POLYTECHNIC UNIVERISTY OF THE PHILIPPINES
COLLEGE OF SCIENCE
Department of Biology
Instructional Manual
in
ENVIRONMENTAL SCIENCE
by:
EnP. Ibylou Bandala-Golla, PhD.
James Santiago
Academic Year 2020 - 2021
Course Description:
Environmental science is the study of interrelationships between humans and the natural
world. Environmental science is an interdisciplinary field that includes both scientific and
social aspects of human impact on the world. The field of environmental science involves
an understanding of scientific principles, economic influences, and political action.
Environmental decisions often involve compromise. A decision that may be supportable
from a scientific or economic point of view may not be supportable from a political point
of view without modification. Often political decisions relating to the environment may
not be supported by economic analysis. A central factor that makes the study of
environmental science so interesting/frustrating/challenging is the high degree of
interrelatedness among seemingly unrelated factors.
General Objectives:
1. Recognize that the field of environmental science includes social, political, and
economic aspects in addition to science.
2. Understand that science is usually reliable because information is gathered in a
manner that requires impartial evaluation and continuous revision.
3. Describe examples that illustrate the interrelated nature of environmental
science.
4. Understand why most social and political decisions are made with respect to
political jurisdictions but environmental problems do not necessarily coincide
with these human-made boundaries.
5. Understand the concept of sustainability.
6. Recognize that human population growth contributes to environmental problems.
7. Recognize that people rely on the services provided by ecosystems.
8. Understand that food security is an issue for many people in the less- developed
world.
9. Recognize that there are governance issues that make it difficult to solve
environmental problems.
10. Recognize that the quality of the environment has an important impact on human
health.
11. Understand that personal security incorporates economic, political, cultural,
social, and environmental aspects.
12. Describe environmental impacts of globalization.
13. Recognize the central role energy use has on environmental problems.
14. Explain the connection between material wealth and resource exploitation.
15. Explain some of the relationships between affluence, poverty, and environmental
degradation.
2
General Instructions
3
Module 1 - Basic Concepts in Ecology and Environmental
Science
Introduction to Environmental Science
What makes Environmental Science different from other
Sciences?
The Scientific Method and Critical Thinking
5
Module 2 - Earth’s Physical Systems: Energy and Geology
Systems and Feedback Loops
Earth’s Energy Source
Earth’s Geological Processes
9
9
11
12
Module 3 – Earth’s Ecological Systems
Earth’s Ecology
Energy Flow through Ecosystems
Biogeochemical Cycles in Ecosystems
16
16
18
20
Module 4 – Evolution, Biodiversity, and Population Ecology
Evolution: An Introduction
Levels of Ecological Organization
Population Ecology
Species Interactions
Ecological Communities
23
23
25
26
27
28
Module 5 - Population Principles and Demography
General Principles of Population Growth
Demography: Principles governing human populations
31
32
41
Module 6 – Earth’s Natural Resources
Food and Soil Resources
Sustainable Agriculture
Water and Air Resources
Petroleum Resources / Fossil Fuels
Nuclear Power
Renewable and Sustainable Energy Resources
50
51
60
62
68
71
75
Module 7 - Global and Regional Environmental Problems:
Causes, Interconnections, and Proposed Solutions
Water Pollution
Air Pollution
Solid and Hazardous Waste
Deforestation
Biodiversity Loss
Global Climate Change
Stratospheric Ozone Depletion
Concept of Sustainable Development
78
79
90
92
99
104
115
119
123
Module 8 - Philippine Agenda
128
Final Output
138
3
5
6
7
General Instructions
Please do not write on this module. Answers to this module should be written on a
separate document. A notebook is preferred bearing the subject title, full name, and
course, year and section. Although it is preferred, it is NOT MANDATORY
.
If a notebook is not possible, you can write your answers on pieces of papers. Compile
your answers and staple them together.
Please DO NOT vandalize, reproduce, modify, distribute, sell, or anything similar in nature
without permission. Unauthorized physical and/or electronic (e.g. web page, social media
account) copies of any part of this module are strictly prohibited.
Follow the format below FOR EVERY ACTVITY that you accomplish. If you have more
than one page for an activity, include still your basic information, and activity and page
number.
Sample format:
Environmental Science
Name: Dela Cruz, Juan
Course, Year, and Section: BS-ABC 1-1
Activity name and number: Activity 01 - Introduction
Grading System:
Quizzes & oral reports (Activities) 70%
Final Exam
30%
100%
Passing grade: 75% (3.0)
General Rubric for Essays
This is the general scoring rubric for grading the essays in this module. Please use this
as a guide when writing essays.
Content (40%)
Essay has a specific central idea that is clearly stated in the opening sentence. It is
appropriate, has concrete details that support the central idea and show originality and
focus.
Research (40%)
Essay has cited researched information and introduced personal ideas to enhance essay
cohesiveness.
Organization (20%)
Essay is logically organized and well-structured. Critical thinking skills are evident.
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MODULE 01
BASIC CONCEPTS IN ECOLOGY AND ENVIRONMENTAL SCIENCE
Time Frame: 1 Week (W2)
Overview:
Lesson 1: Introduction to Environmental Science
Lesson 2: What makes Environmental Science different from other Sciences
Objectives:
1. Define and articulate some common environmental terminologies
2. Define ecology and enumerate the different hierarchical levels of ecology.
3. Recognize that the field of environmental science includes social, political, and
economic aspects in addition to science.
4. Differentiate Environmental Science, Environmental Studies and
Environmentalism
5. Understand that science is mostly reliable because information is gathered in a
manner that requires impartial evaluation and continuous revision.
6. Describe examples that illustrate the interrelated nature of environmental
science.
7. Understand that knowing probability reduces uncertainty.
8. Acknowledge that science is a cumulative process
9. Explain and apply the scientific method.
I.
Introduction to Environmental Science
Our environment surrounds us. Our environment consists of all the living and non-living
things around us. It encompasses built environments – structures and living spaces –
as well as natural components such as plants and animals. The fundamental insight of
environmental science is that we humans are a part of the natural world, not separate
from it, and we are dependent on a healthy, functioning planet.
The terms ecology, environmentalism, environmental studies, and environmental science
are often used interchangeably. This leads to misconceptions and confusion by the
general public.
1. Ecology – the scientific study of the interrelations of organisms and their
environments. Ecology as a science plays an important role in our understanding
of various ecosystems. It is an interdisciplinary field that includes both biology and
earth science, but is a separate area of study from environmentalism, natural
history, and environmental science.
Ecologists study populations and communities of living organisms, physiological
and behavioral adaptations of species to their environment, interactions among
species and functions of ecosystems such as energy flow and nutrient cycling.
Ecologists may study plants or animals in terrestrial, fresh water, or marine
environments, and in tropical, temperate, or polar regions
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2. Environmentalism - Environmentalism refers to a way of thinking and a
movement of political activism based on a common conviction that our natural
environment should be protected. It takes many forms, from local homeowners
organizing grassroots activities to fishermen banding together to stop pollution,
and extends to national and international activities.
The motivations of environmentalists are often health-related (preventing
contaminant poisoning), economic (maintaining valuable natural resources such
as fisheries), or aesthetic (maintaining a more attractive place to live).
3. Environmental Science - focuses on the interactions between the physical,
chemical, and biological components of the environment, including their effects on
all types of organisms.
Environmental Scientists study, develop, implement and advise on policies and
plans for managing and protecting the environment, flora, fauna and other natural
resources. Environmental Scientists also ensure to incorporate sustainable
practices (social, economic, and environmental) into all levels of operations of
various industry such as oil and gas, and the mining industry.
II.
What make environmental science different from other sciences
People depend on the environment. People can live only in an environment with certain
kinds of characteristics and within certain ranges of availability of resources. Because
modern science and technology give us the power to affect the environment, we have to
understand how the environment works, so that we can live within its constraints.
Environmental Science involves many sciences
•
Environmental Science is interdisciplinary in nature, it integrates many
disciplines such as biology, geology, hydrology, climatology, meteorology,
oceanography, and soil science among others.
Environmental Science also involves nonscientific fields that we have to do with how we
value environment.
•
Environmental Science also encompasses other fields such as anthropology,
economics, history, and philosophy. In order to gather to gather the best
information to address environmental concerns, we be aware of the cultural and
historical contexts in which we make decisions about the environment.
Environmental Science deals with many topics that have great emotional effects on
people, and therefore are subject to debate and to strong feelings that often ignore
scientific information.
•
The field of Environmental Science also integrates natural sciences with
environmental law, environmental impact, and environmental planning.
6
Finding solutions to environmental problems involves more than simply gathering facts
and understanding the scientific issues of a particular problem. It also has much to do
with our systems of values and issues of social justice. To solve our environmental
problems, we must understand what our values are and which potential solutions are
socially just. Then we can apply scientific knowledge about specific problems and find
acceptable solutions.
III.
The scientific method and critical thinking
The scientific method is a technique for testing ideas with observations. It includes several
assumptions and a series of interrelated steps.
The assumptions are:
a. The universe functions in accordance with fixed natural laws.
b. All events arise from some cause and, in turn, cause other events.
c. We can use our senses and reasoning abilities to detect and describe natural laws.
The steps of the scientific method are:
a. Make observations.
b. Ask questions - Determining which questions to ask is one of the most important
steps in the investigation process.
c. Develop a hypothesis.
d. Make predictions.
e. Test the predictions.
f. Analyze and interpret results.
It is important to distinguish between observations and inferences.
•
Observations, the basis of science, may be made through any of the five
senses or by instruments that measure beyond what we can sense.
o
•
We might observe that a substance is a white, crystalline material with a
sweet taste.
Inferences are generalizations that arise from a set of observations. When
everyone or almost everyone agrees with what is observed about a particular
thing, the inference is often called a fact.
o
We might infer from these observations alone that the substance is sugar.
When scientists wish to test an inference, they convert it into a hypothesis, which is a
statement that can be disproved. The hypothesis continues to be accepted until it is
disproved. In testing a hypothesis, a scientist tries to keep all relevant variables constant
except for the independent and dependent variables. An experiment is an activity
designed to test the validity of a hypothesis; it involves manipulating variables, or
conditions that can change. In a controlled experiment, the experiment is compared to
a standard, or control—an exact duplicate of the experiment except for the one variable
being tested (the independent variable). Any difference in outcome (dependent variable)
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between the experiment and the control can be attributed to the effect of the independent
variable.
When variables cannot be manipulated - climate change is an example of this - a natural
experiment is performed. In such experiments, researchers test their hypothesis by
searching for correlation, a statistical relationship between variables. Natural experiments
provide evidence that is weaker than manipulative experiments but can still make for
strong science.
Science is based on inductive reasoning, also called induction: It begins with specific
observations and then extends to generalizations, which may be disproved by testing
them. If such a test cannot be devised, then we cannot treat the generalization as a
scientific statement. Although new evidence can disprove existing scientific theories,
science can never provide absolute proof of the truth of its theories.
A scientific theory is a grand scheme that relates and explains many observations and
is supported by a great deal of evidence.
Scientists record data from their studies and analyze the data using statistical tests to see
if the hypothesis is supported. If the results disprove a hypothesis, the hypothesis is
rejected and a new one may be proposed. If the repeated tests fail to reject a particular
hypothesis, it will ultimately be accepted as true.
Scientists use accumulated knowledge to develop explanations that are consistent with
currently accepted hypotheses. Sometimes an explanation is presented as a model. A
model is “a deliberately simplified construct of nature.” It may be a physical working model,
a pictorial model, a set of mathematical equations, or a computer simulation.
Measurements are approximations that may be more or less exact, depending on the
measuring instruments and the people who use them. A measurement is meaningful
when accompanied by an estimate of the degree of uncertainty, or error. Accuracy in
measurement is the extent to which the measurement agrees with an accepted value.
Precision is the degree of exactness with which a measurement is made. A precise
measurement may not be accurate. The estimate of uncertainty provides information on
the precision of a measurement.
The scientific process does not stop with the scientific method.
a. Peer review. Research results are submitted to a journal for publication. Other
scientists who specialize in the subject area are asked to provide comments and
critiques and judge whether the work merits publication. This process is known as
peer review.
b. Conference presentations. Scientists frequently present their work at professional
conferences and receive informal comments on their work prior to publication.
c. Grants and funding. Most scientists spend considerable time writing grant
applications to private foundations or government agencies for support of their
research. These applications are also usually subjected to peer review. Conflicts
of interest sometimes arise when results are in conflict with the interests of the
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funding agency. This has occurred in the case of private industry funding.
Government agencies have also occasionally suppressed findings to avoid policy
implications.
d. Repeatability. The careful scientist may test a hypothesis repeatedly in various
ways before submitting it for publication. After publication, other scientists will
attempt to reproduce the results in their own analyses.
e. Theories. If a hypothesis survives repeated testing by numerous research teams,
it may be incorporated into a theory. A theory is a widely accepted, well-tested
explanation of one or more cause and effect relationships that has been
extensively validated by a large amount of research. In science, a theory is not
speculation or hypothesis.
f.
Applications. Knowledge gained from scientific research may be applied to help
fulfill society’s needs and address society’s problems. A correct social response
may still be difficult even when the scientific information is clear, however.
Activity
1. In your own understanding, define the term environment and describe the field of
environmental science.
2. Explain the importance of natural resources and ecosystem services in our lives.
MODULE 02
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EARTH’S PHYSICAL SYSTEMS: ENERGY AND GEOLOGY
Time Frame: 1 Week (W3)
Overview:
Lesson 1: Systems and feedback Loops
Lesson 2: Earth’s Energy Sources
Lesson 3: The Geological Processes
Objectives:
1.
Describe and explain the components and functions of systems.
2.
Explain different model systems and how do feedback loops affect them
3.
Differentiate among forms of energy and explain the basics of energy flow
Distinguish photosynthesis, cellular respiration, and chemosynthesis, and
summarize their importance to living things
4.
Explain how plate tectonics and the rock cycle shape the landscape around us and
the earth beneath our feet
5.
List major types of geologic hazards and describe ways to mitigate their impacts
I.
SYSTEMS AND FEDBACK LOOPS
•
A system is a network of relationships among a group of parts, elements, or
components that interact with and influence one another through the exchange of
energy, matter, and/or information. A single organism, such as your body, is a
system, as are a sewage-treatment plant, a city, and a river. On a much different
scale, the entire Earth is a system. In a broader sense, a system is any part of the
universe you can isolate in thought (in your brain or on your computer) or, indeed,
physically, for the purpose of study.
•
Systems receive inputs, process them, and produce outputs. Systems can have
many inputs, processes, and outputs. Sometimes a system’s output can serve as
an input to that same system in a circular process called a feedback loop.
•
In a negative feedback loop, output driving the system in one direction acts as
input that moves the system in the other direction. Negative feedback loops are
not ―bad feedback loops. They generally stabilize a system. In a positive
feedback loop, the output drives the system further toward one extreme. Positive
feedback loops are usually not ―good; they tend to destabilize a system. Positive
feedback is rare in natural systems not impacted by human behavior.
The inputs and outputs of a complex natural system often occur simultaneously,
keeping the system constantly active. But even processes moving in opposite
directions can be stabilized by negative feedback so that their effects balance out,
creating a state of dynamic equilibrium. Processes in dynamic equilibrium
contribute to homeostasis, where the tendency of the system is to maintain stable
internal conditions. Sometimes processes have to be viewed over long time
periods to see this stability.
•
10
•
It is difficult to fully understand systems by focusing on their individual components
because systems can show emergent properties, characteristics that are not
evident in the system’s components. Systems rarely have well-defined boundaries,
so deciding where one system ends and another begins can be difficult. Systems
may exchange energy, matter, and information with other systems, or may contain
or be contained within other systems.
•
We may perceive Earth’s systems in various ways. The lithosphere is everything
that is solid earth beneath our feet. The atmosphere is comprised of the air
surrounding our planet. The hydrosphere encompasses all water in surface bodies,
underground, and in the atmosphere. The biosphere consists of all the planet’s
living organisms, or biotic components, and the abiotic portions of the environment
with which they interact. All of these systems interact and their boundaries overlap.
Ultimately, it is impossible to isolate any one in discussing an environmental
system.
II.
•
EARTH’S ENERGY SOURCE
Energy is the capacity to change the position, physical composition, or
temperature of matter – in other words, a force than can accomplish work. Energy
comes in different forms.
1. Potential energy is the energy of position.
2. Kinetic energy is the energy of motion. It can be expressed as heat
energy, light energy, sound energy, or electrical energy as well.
3. Chemical energy is a special type of potential energy that is held in the
bonds between atoms. Converting a molecule with high-energy bonds
into molecules with lower-energy bonds releases energy by changing
potential energy into kinetic energy.
4. Nuclear energy, the energy in an atomic nucleus, and mechanical energy,
such as that stored in a compressed spring, are also potential energies.
•
Energy is always conserved but can change in quality. The first law of
thermodynamics states that energy can change from one form to another, but
cannot be created or lost. For example, when heated underground water surges
to the surface, the kinetic energy of its movement will equal the potential energy it
held underground. The second law of thermodynamics states that energy tends
to change from a more-ordered state to a less-ordered state, as long as no force
counteracts this tendency. Systems tend to move toward increasing disorder, or
entropy. The order of an object or system can be increased through the input of
additional energy from outside the system. Living organisms maintain their
structure and function by consuming energy (food). The nature of an energy
source determines how easily people can harness it. In every transfer of energy,
some portion escapes. The degree to which we successfully capture energy is
termed the energy conversion efficiency and is the ratio of useful output of energy
to the amount that needs to be input.
•
Light energy from the sun powers most living systems. Some organisms use the
sun’s radiation to produce their own food. Such organisms are called autotrophs
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or primary producers and include green plants, algae, and cyanobacteria.
Autotrophs turn light energy from the sun into chemical energy in a process called
photosynthesis. In photosynthesis, sunlight powers a series of chemical reactions
that converts water and carbon dioxide into sugars and oxygen, transforming
diffuse energy from the sun into concentrated energy the organism can use.
•
Photosynthesis produces food for plants and animals In a series of chemical
reactions called light reactions, photosynthesis uses solar energy to split water
molecules to form hydrogen ions and the oxygen we breathe. The light reactions
produce energy molecules that fuel reactions in the Calvin cycle where sugars are
formed. The net process of photosynthesis is defined by the chemical equation:
6CO2 + 6H2O + the sun’s energy → C6H1206 (sugar) + 6O2. Animals depend on
the sugars and oxygen from photosynthesis. E. Cellular respiration releases
chemical energy. Organisms make use of the chemical energy created by
photosynthesis in a process called cellular respiration, which is vital to life. Cells
employ oxygen to convert glucose back into its original starting materials, water
and carbon dioxide, and release energy to form chemical bonds or perform other
tasks within cells. The net equation for cellular respiration is the exact opposite of
that for photosynthesis: C6H12O6 (sugar) + 6O2 → 6CO2 + 6H2O + energy The
energy released per glucose molecule in respiration is only two thirds of the
energy input per glucose molecule in photosynthesis, an example of the second
law of thermodynamics. Cellular respiration occurs in all living things and in both
the autotrophs that create glucose and in heterotrophs, or consumers.
•
Geothermal energy also powers Earth’s systems. A minor energy source is the
gravitational pull of the moon, which, in conjunction with the sun, causes ocean
tides. A more significant additional energy source is the geothermal heating
emanating from inside the earth, powered primarily by radiation from radioisotopes
deep inside our planet.
•
Hydrothermal vents are areas in the deep ocean from which jets of geothermally
heated water emerge. Hydrothermal vent communities utilize chemical energy
instead of light energy. Communities of living organisms at these locations
depend on bacteria at the base of the food web; these bacteria fuel themselves
by chemosynthesis using the chemical bond energy of hydrogen sulfide: 6CO2 +
6H2O + 3 H2S → C6H12O6 (sugar) + 3H2SO4
III.
EARTH’S GEOLOGICAL PROCESSES
•
A good place to begin understanding how our planet functions is right beneath our
feet: rocks, soil, and sediments. Our planet is dynamic and this dynamism is what
motivates geology, the study of Earth’s physical features, processes and history.
Two geological processes of fundamental importance are plate tectonics and the
rock cycle.
•
Most geological processes take place near the Earth’s surface. Earth’s center is
a dense core consisting mostly of iron, solid in the inner core and molten in the
outer core. Surrounding the core is a less dense, elastic layer called the mantle.
A portion of the upper mantle is the asthenosphere, which contains soft rock.
Above that is the harder rock we know as the lithosphere. The lithosphere includes
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the Earth’s crust, the thin layer of rock that covers the surface. The heat from inner
Earth rises to the surface and dissipates. Where the asthenosphere approaches
within a few miles of the surface, we can drill to tap geothermal energy. But the
soil and rock just below the Earth’s surface is fairly constant in temperature,
(cooler than the air in summer and warmer than the air in winter), allowing homes
to use geothermal energy efficiently. The heat from the inner layers of the Earth
also drives convection currents that move mantle material. As this material moves
it drags lithospheric plates along the surface. This movement is known as plate
tectonics.
•
Plate tectonics shape Earth’s geography. Our planet’s surface consists of about
15 major tectonic plates which move at rates of roughly 2 to 15 cm per year. The
plates’ movement has influenced Earth’s climate and life’s evolution. There are
three types of plate boundaries.
•
At divergent plate boundaries, tectonic plates push apart as magma rises upward
to the surface, creating new crust as it cools. An example is the Mid-Atlantic ridge.
Where two plates meet, they may slip and grind alongside one another, forming a
transform plate boundary or a fault. The San Andreas Fault in California is an
example of this type of boundary. When plates collide at convergent plate
boundaries, two scenarios are possible. One plate may slide beneath the other in
a process called subduction. This can lead to volcanic eruptions. The Cascades
in the Pacific Northwest are an example and led to the eruption of Mount Saint
Helens in 1980 and 2004. When two plates of continental lithosphere meet, the
continental crust on both sides resists subduction and instead crushes together,
bending, buckling, and deforming layers of rock from both plates in a continental
collision. The Himalayas were formed in this manner and continue to be uplifted.
•
Tectonics produce Earth’s landforms. Tectonic processes shape climate and life’s
evolution by changing areas of coastal regions to continental interiors and the
reverse.
Over geological time, rocks and the minerals that comprise them are heated,
melted, cooled, broken down, and reassembled in a very slow process called the
rock cycle. A rock is any solid aggregation of minerals. A mineral is any naturally
occurring solid element of inorganic compound with a crystal structure, a specific
chemical composition, and distinct physical properties.
•
•
If magma is released through the lithosphere, it may flow or splatter across Earth’s
surface as lava. Rock that forms when lava cools is called igneous rock. There
are two main classes of igneous rock. Intrusive igneous rock forms when magma
cools slowly and solidifies while it is below the Earth’s surface, giving rise to rocks
with large crystals such as granite. The second class is formed when molten rock
is ejected from a volcano and cools quickly. This class is called extrusive igneous
rock and its most common representative is basalt.
•
Through weathering, particles of rock blown by wind or washed away by water
come to rest downhill, downstream, or downwind from their sources, eventually
forming sediments. Sediments can also form chemically from the precipitation of
substances out of solution. Sedimentary rock is formed as sediments are
physically pressed together; dissolved minerals bind the particles together in a
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process known as lithification. Sandstone, shale, and limestone are examples of
sedimentary rock. These processes also create the fossils of organisms and the
fossil fuels we use for energy.
•
When any type of rock is subjected to great heat and pressure, such as from
geologic forces deep underground, it may alter its form, becoming metamorphic
rock. Metamorphic rock includes slate and marble.
•
Geologic and Natural Hazards Earth’s geothermal heating gives rise to creative
forces that shape our planet. They can include hazards such as earthquakes and
volcanoes. Nine out of ten of the world’s earthquakes and over half of the world’s
volcanoes occur on plate boundaries that are on the circum-Pacific belt, the socalled “ring of fire.” large amount of ash and cinder in a sudden explosion, such
as during Mount Saint Helen’s 1980 eruption. Volcanic eruptions exert
environmental impacts. Large eruptions can depress temperatures throughout the
world as a result of ash blocking sunlight and sulfuric acid hazes that block
radiation and cool the atmosphere.
•
Landslides are a form of mass wasting. A landslide occurs when large amounts of
rock or soil collapse and flow downhill. Landslides are a severe and sudden
•
Earthquakes result from movement at plate boundaries and faults. Plate
boundaries and other places where faults occur may relieve built up pressure in
fits and starts. Each release of energy causes what we know as an earthquake.
Damage from earthquakes is generally greatest where soils are loose or saturated
with water. Engineers have developed ways to protect buildings from earthquakes
and such designs are an important part of new building codes in earthquake-prone
areas such as California and Japan.
•
Volcanoes arise from rifts, subduction zones, or hotspots. Where molten rock, hot
gas, or ash erupt through the Earth’s surface, a volcano is formed, often creating
a mountain over time as cooled lava accumulates. At some volcanoes, such as
Mount Kilauea in Hawaii, lava flows continuously downhill. At others, a volcano
may let loose manifestation of mass wasting, the downslope movement of soil and
rock due to gravity. Mass wasting can be brought about by human land practices
that expose or loosen soil. Mass wasting events can be colossal and deadly, such
as the mudslides that occur after torrential hurricane rainfall or following volcanic
eruptions.
•
Tsunamis can follow earthquakes, volcanoes, or landslides. Earthquakes,
volcanic eruptions, and large coastal landslides can all displace huge volumes of
ocean water instantaneously and trigger a tsunami, an immense swell or wave of
water that can travel thousands of miles across oceans. Residents of the United
States are vulnerable to tsunamis as well. A Canary Island volcano could put
Atlantic-coast cities at risk.
•
We can worsen or mitigate the impacts of natural hazards. Flooding, coastal
erosion, wildfire, tornadoes, and hurricanes are “natural hazards” whose impacts
can be worsened by the choices that we make. As the population grows, more
people live in areas susceptible to disaster, sometimes by choice.
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•
We use and engineer landscapes in ways that can increase the severity of natural
hazards. As we change Earth’s climate by emitting greenhouse gases, we alter
patterns of precipitation, increasing risks of drought, flooding and fire. Rising sea
levels increase coastal erosion. We can reduce the impacts of hazards through
the thoughtful use of technology and a solid understanding of geology and ecology.
Activity
1. Identify at least five (5) of the natural ang geologic hazard the Philippines have
encountered in the past decade. As regular citizens, how can we contribute to
mitigate the impact of the identified natural hazards?
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MODULE 03
EARTH’S ECOLOGICAL SYSTEMS
Time Frame: 3 Weeks (W4-6)
Overview:
Lesson 1: The Earth’s Ecology
Lesson 2: Energy flow through ecosystems
Lesson 3: Biogeochemical cycles in ecosystems
Objectives:
1.
Enumerate the different components of ecosystems
2.
Enumerate and define the different biomes.
3.
Identify and list abiotic and biotic factors in an ecosystem.
4.
Explain the significance of limiting factors.
5.
Articulate the processes involved in the flow of energy through ecosystems.
6.
Trace and explain how different forms of matter such as water, carbon, nitrogen,
phosphorus, and sulfur are transferred across the different components of the
ecosystem.
7.
Describe energy flow through an ecosystem.
8.
Relate the concepts of food webs and food chains to trophic levels.
9.
Describe the role of producers, consumers, and decomposers in the cycling of
carbon atoms through ecosystems.
I. The Earth’s Ecology
•
Ecology is the scientific study of relationships in the natural world. It includes
relationships between organisms and their physical environments (physiological
ecology); between organisms of the same species (population ecology); between
organisms of different species (community ecology); and between organisms and
the fluxes of matter and energy through biological systems (ecosystem ecology).
Ecologists study these interactions in order to understand the abundance and
diversity of life within Earth's ecosystems—in other words, why there are so many
plants and animals, and why there are so many different types of plants and
animals.
•
Geography has a profound impact on ecosystems because global circulation
patterns and climate zones set basic physical conditions for the organisms that
inhabit a given area. The most important factors are temperature ranges, moisture
availability, light, and nutrient availability, which together determine what types of
life are most likely to flourish in specific regions and what environmental
challenges they will face.
•
Earth is divided into distinct climate zones that are created by global circulation
patterns. The tropics are the warmest, wettest regions of the globe, while
subtropical high-pressure zones create dry zones at about 30° latitude north and
south. Temperatures and precipitation are lowest at the poles. These conditions
16
create biomes— broad geographic zones whose plants and animals are adapted
to different climate patterns. Since temperature and precipitation vary by latitude,
Earth's major terrestrial biomes are broad zones that stretch around the globe.
Each biome contains many ecosystems (smaller communities) made up of
organisms adapted for life in their specific settings.
•
Land biomes are typically named for their characteristic types of vegetation, which
in turn influence what kinds of animals will live there. Soil characteristics also vary
from one biome to another, depending on local climate and geology. compares
some key characteristics of three of the forest biomes. Aquatic biomes (marine
and freshwater) cover three-quarters of the Earth's surface and include rivers,
lakes, coral reefs, estuaries, and open ocean. The distribution of temperature, light,
and nutrients set broad conditions for life in aquatic biomes in much the same way
that climate and soils do for land biomes. Marine and freshwater biomes change
daily or seasonally. For example, in the intertidal zone where the oceans and land
meet, areas are submerged and exposed as the tide moves in and out. During the
winter months lakes and ponds can freeze over, and wetlands that are covered
with water in late winter and spring can dry out during the summer months. There
are important differences between marine and freshwater biomes. The oceans
occupy large continuous areas, while freshwater habitats vary in size from small
ponds to lakes covering thousands of square kilometers. As a result, organisms
that live in isolated and temporary freshwater environments must be adapted to a
wide range of conditions and able to disperse between habitats when their
conditions change or disappear.
•
Aquatic and coastal systems also show biome-like patterns. One might consider
the shallows along the world’s coastlines to represent one aquatic system, the
continental shelves another, and the open ocean, deep sea, coral reefs, and kelp
forests as still other distinct sets of communities. Many coastal systems—such as
salt marshes, rocky intertidal communities, mangrove forests and estuaries—
share both terrestrial and aquatic components. Freshwater systems such as those
in the Great Lakes are widely distributed throughout the world.
We can divide the world into various terrestrial biomes.
1. Temperate deciduous forest is found in eastern North America and is characterized by
broadleaf trees that lose their leaves in the fall.
2. Moving westward from the Great Lakes, we find temperate grasslands that were once
widespread but have now been mostly converted to agricultural land.
3. Temperate rainforest is found in the Pacific Northwest and is a forest type known for
its high biodiversity and potential to produce large volumes of commercially important
products.
4. Tropical rainforest is found in regions near the equator, and is characterized by high
rainfall year-round, uniformly warm temperatures, high biodiversity, and lush vegetation.
5. Tropical areas that are warm year-round but where rainfall is lower overall and highly
seasonal give rise to tropical dry forests, or tropical deciduous forests.
6. Dry tropical areas across large stretches of Africa, South America, India, and Australia
are savannas—regions of grasslands interspersed with clusters of trees.
7. Desert is the driest biome on Earth, and much of the rainfall occurs during isolated
storms. Deserts are not always hot, but they have low humidity and relatively little
17
vegetation to insulate them. Temperatures, therefore, may vary widely from day to night
and across seasons.
8. Tundra is nearly as dry as desert, but is located in cold regions at very high latitudes
along the northern edges of Russia, Canada, and Scandinavia. Little daylight in winter
and lengthy, cool days in summer result in a landscape of lichens and low, scrubby
vegetation without trees.
9. The northern coniferous forest, or boreal forest, often called taiga, develops in cooler,
drier regions than temperate rainforests. Taigas stretch in a broad band across much of
Canada, Alaska, Russia, and Scandinavia.
10. Chaparral is found in areas of Mediterranean climate, and consists of densely
thicketed evergreen shrubs.
•
Since biomes represent consistent sets of conditions for life, they will support
similar kinds of organisms wherever they exist, although the species in the
communities in different places may not be taxonomically related. For example,
large areas of Africa, Australia, South America, and India are covered by
savannas (grasslands with scattered trees). The various grasses, shrubs, and
trees that grow on savannas all are generally adapted to hot climates with distinct
rainy and dry seasons and periodic fires, although they may also have
characteristics that make them well-suited to specific conditions in the areas
where they appear.
•
Species are not uniformly spread among Earth's biomes. Tropical areas generally
have more plant and animal biodiversity than high latitudes, measured in species
richness (the total number of species present). This pattern, known as the
latitudinal biodiversity gradient, exists in marine, freshwater, and terrestrial
ecosystems in both hemispheres.
II. Energy flow through ecosystems
•
Ecosystems maintain themselves by cycling energy and nutrients obtained from
external sources. At the first trophic level, primary producers (plants, algae, and
some bacteria) use solar energy to produce organic plant material through
photosynthesis. Herbivores—animals that feed solely on plants—make up the
second trophic level. Predators that eat herbivores comprise the third trophic level;
if larger predators are present, they represent still higher trophic levels. Organisms
that feed at several trophic levels (for example, grizzly bears that eat berries and
salmon) are classified at the highest of the trophic levels at which they feed.
Decomposers, which include bacteria, fungi, molds, worms, and insects, break
down wastes and dead organisms and return nutrients to the soil. On average
about 10 percent of net energy production at one trophic level is passed on to the
next level. Processes that reduce the energy transferred between trophic levels
include respiration, growth and reproduction, defecation, and nonpredatory death
(organisms that die but are not eaten by consumers). The nutritional quality of
material that is consumed also influences how efficiently energy is transferred,
because consumers can convert high-quality food sources into new living tissue
more efficiently than low-quality food sources. The low rate of energy transfer
between trophic levels makes decomposers generally more important than
producers in terms of energy flow. Decomposers process large amounts of
18
organic material and return nutrients to the ecosystem in inorganic form, which
are then taken up again by primary producers. Energy is not recycled during
decomposition, but rather is released, mostly as heat (this is what makes compost
piles and fresh garden mulch warm).
•
An ecosystem's gross primary productivity (GPP) is the total amount of organic
matter that it produces through photosynthesis. Net primary productivity (NPP)
describes the amount of energy that remains available for plant growth after
subtracting the fraction that plants use for respiration. Productivity in land
ecosystems generally rises with temperature up to about 30°C, after which it
declines, and is positively correlated with moisture. On land primary productivity
thus is highest in warm, wet zones in the tropics where tropical forest biomes are
located. In contrast, desert scrub ecosystems have the lowest productivity
because their climates are extremely hot and dry.
•
In the oceans, light and nutrients are important controlling factors for productivity.
Light penetrates only into the uppermost level of the oceans, so photosynthesis
occurs in surface and near-surface waters. Marine primary productivity is high
near coastlines and other areas where upwelling brings nutrients to the surface,
promoting plankton blooms. Runoff from land is also a source of nutrients in
estuaries and along the continental shelves. Among aquatic ecosystems, algal
beds and coral reefs have the highest net primary production, while the lowest
rates occur in the open due to a lack of nutrients in the illuminated surface layers
•
How many trophic levels can an ecosystem support? The answer depends on
several factors, including the amount of energy entering the ecosystem, energy
loss between trophic levels, and the form, structure, and physiology of organisms
at each level. At higher trophic levels, predators generally are physically larger
and are able to utilize a fraction of the energy that was produced at the level
beneath them, so they have to forage over increasingly large areas to meet their
caloric needs. Because of these energy losses, most terrestrial ecosystems have
no more than five trophic levels, and marine ecosystems generally have no more
than seven. This difference between terrestrial and marine ecosystems is likely
due to differences in the fundamental characteristics of land and marine primary
organisms. In marine ecosystems, microscopic phytoplankton carry out most of
the photosynthesis that occurs, while plants do most of this work on land.
Phytoplankton are small organisms with extremely simple structures, so most of
their primary production is consumed and used for energy by grazing organisms
that feed on them. In contrast, a large fraction of the biomass that land plants
produce, such as roots, trunks, and branches, cannot be used by herbivores for
food, so proportionately less of the energy fixed through primary production travels
up the food chain. Growth rates may also be a factor. Phytoplankton are extremely
small but grow very rapidly, so they support large populations of herbivores even
though there may be fewer algae than herbivores at any given moment. In contrast,
land plants may take years to reach maturity, so an average carbon atom spends
a longer residence time at the primary producer level on land than it does in a
marine ecosystem. In addition, locomotion costs are generally higher for terrestrial
organisms compared to those in aquatic environments. The simplest way to
describe the flux of energy through ecosystems is as a food chain in which energy
passes from one trophic level to the next, without factoring in more complex
19
relationships between individual species. Some very simple ecosystems may
consist of a food chain with only a few trophic levels. For example, the ecosystem
of the remote wind-swept Taylor Valley in Antarctica consists mainly of bacteria
and algae that are eaten by nematode worms . More commonly, however,
producers and consumers are connected in intricate food webs with some
consumers feeding at several trophic levels.
•
An important consequence of the loss of energy between trophic levels is that
contaminants collect in animal tissues—a process called bioaccumulation. As
contaminants bioaccumulate up the food web, organisms at higher trophic levels
can be threatened even if the pollutant is introduced to the environment in very
small quantities.
III. Biogeochemical cycles in ecosystems
•
Biogeochemical Cycling in Ecosystems Along with energy, water and several
other chemical elements cycle through ecosystems and influence the rates at
which organisms grow and reproduce. About 10 major nutrients and six trace
nutrients are essential to all animals and plants, while others play important roles
for selected species. The most important biogeochemical cycles affecting
ecosystem health are the water, carbon, nitrogen, and phosphorus cycles. As
noted earlier, most of the Earth's area that is covered by water is ocean. In terms
of volume, the oceans dominate further still: nearly all of Earth's water inventory
is contained in the oceans (about 97 percent) or in ice caps and glaciers (about 2
percent), with the rest divided among groundwater, lakes, rivers, streams, soils,
and the atmosphere. In addition, water moves very quickly through land
ecosystems. These two factors mean that water's residence time in land
ecosystems is generally short, on average one or two months as soil moisture,
weeks or months in shallow groundwater, or up to six months as snow cover. But
land ecosystems process a lot of water: almost two-thirds of the water that falls on
land as precipitation annually is transpired back into the atmosphere by plants,
with the rest flowing into rivers and then to the oceans. Because cycling of water
is central to the functioning of land ecosystems, changes that affect the hydrologic
cycle are likely to have significant impacts on land ecosystems. Both land and
ocean ecosystems are important sinks for carbon, which is taken up by plants and
algae during photosynthesis and fixed as plant tissue.
•
Carbon cycles relatively quickly through land and surface-ocean ecosystems, but
may remain locked up in the deep oceans or in sediments for thousands of years.
The average residence time that a molecule of carbon spends in a terrestrial
ecosystem is about 17.5 years, although this varies widely depending on the type
of ecosystem: carbon can be held in old-growth forests for hundreds of years, but
its residence time in heavily grazed ecosystems where plants and soils are
repeatedly turned over may be as short as a few months. Human activities,
particularly fossil fuel combustion, emit significant amounts of carbon each year
over and above the natural carbon cycle. Currently, human activities generate
about 7 billion tons of carbon per year, of which 3 billion tons remain in the
atmosphere. The balance is taken up in roughly equal proportions by oceans and
land ecosystems. Identifying which ecosystems are absorbing this extra carbon
and why this uptake is occurring are pressing questions for ecologists. Currently,
20
it is not clear what mechanisms are responsible for high absorption of carbon by
land ecosystems. One hypothesis suggests that higher atmospheric CO2
concentrations have increased the rates at which plants carry out photosynthesis
(so-called CO2 fertilization), but this idea is controversial. Controlled experiments
have shown that elevated CO2 levels are only likely to produce short-term
increases in plant growth, because plants soon exhaust available supplies of
important nutrients such as nitrogen and phosphorus that also are essential for
growth.
•
Nitrogen and phosphorus are two of the most essential mineral nutrients for all
types of ecosystems and often limit growth if they are not available in sufficient
quantities. (This is why the basic ingredients in plant fertilizer are nitrogen,
phosphorus, and potassium, commonly abbreviated as NPK.) A slightly expanded
version of the basic equation for photosynthesis shows how plants use energy
from the sun to turn nutrients and carbon into organic compounds: CO2 + PO4
(phosphate) + NO3 (nitrate) + H2O → CH2O, P, N (organic tissue) + O2 Because
atmospheric nitrogen (N2) is inert and cannot be used directly by most organisms,
microorganisms that convert it into usable forms of nitrogen play central roles in
the nitrogen cycle. So-called nitrogen-fixing bacteria and algae convert ammonia
(NH4) in soils and surface waters into nitrites (NO2) and nitrates (NO3), which in
turn are taken up by plants. Some of these bacteria live in mutualistic relationships
on the roots of plants, mainly legumes (peas and beans), and provide nitrate
directly to the plants; farmers often plant these crops to restore nitrogen to
depleted soils. At the back end of the cycle, decomposers break down dead
organisms and wastes, converting organic materials to inorganic nutrients. Other
bacteria carry out denitrification, breaking down nitrate to gain oxygen and
returning gaseous nitrogen to the atmosphere. Human activities, including fossil
fuel combustion, cultivation of nitrogen-fixing crops, and rising use of nitrogen
fertilizer, are altering the natural nitrogen cycle. Together these activities add
roughly as much nitrogen to terrestrial ecosystems each year as the amount fixed
by natural processes; in other words, anthropogenic inputs are doubling annual
nitrogen fixation in land ecosystems.
•
The main effect of this extra nitrogen is over-fertilization of aquatic ecosystems.
Excess nitrogen promotes algal blooms, which then deplete oxygen from the water
when the algae die and decompose. Additionally, airborne nitrogen emissions
from fossil fuel combustion promote the formation of ground-level ozone,
particulate emissions, and acid rain.
•
Phosphorus, the other major plant nutrient, does not have a gaseous phase like
carbon or nitrogen. As a result, it cycles more slowly through the biosphere. Most
phosphorus in soils occurs in forms that organisms cannot use directly, such as
calcium and iron phosphate. Usable forms (mainly orthophosphate, or PO4) are
produced mainly by decomposition of organic material, with a small contribution
from weathering of rocks amount of phosphate available to plants depends on soil
pH. At low pH, phosphorus binds tightly to clay particles and is transformed into
relatively insoluble forms containing iron and aluminum. At high pH, it is lost to
other inaccessible forms containing calcium. As a result, the highest
concentrations of available phosphate occur at soil pH values between 6 and 7.
Thus soil pH is an important factor affecting soil fertility. Excessive phosphorus
21
can also contribute to over-fertilization and eutrophication of rivers and lakes.
Human activities that increase phosphorus concentrations in natural ecosystems
include fertilizer use, discharges from wastewater treatment plants, and use of
phosphate detergents
Activity
1. Read and study Executive Order 533 s. 2006 – Integrated Coastal Management
Policy.
2. With your understanding on Biogeochemical Cycle, would you agree that EO 533
would ensure the sustainable management of coastal and marine resources?
22
MODULE 04
EVOLUTION, BIODIVERSITY, AND POPULATION ECOLOGY
Time Frame: 3 Weeks (W7-9)
Overview:
Lesson 1: Evolution: An Introduction
Lesson 2: Levels of Ecological Organization
Lesson 3: Species Interaction
Lesson 4: Population Ecology
I.
Evolution: An Introduction
1.
A species is a particular type of organism that shares certain characteristics and
can breed with one another and produce fertile offspring. A population is a group
of individuals of a particular species that live in a particular area. Biological
evolution consists of genetic change in organisms across generations. Natural
selection is the process by which inherited characteristics that enhance survival
and reproduction are passed on more frequently to future generations, altering the
genetic makeup of populations through time.
2.
In 1858, Charles Darwin and Alfred Russell Wallace each independently proposed
the concept of natural selection as a mechanism for evolution and as a way to
explain the great variety of living things.
a.
b.
c.
d.
Individuals of the same species vary in their characteristics.
Organisms produce more offspring than can possibly survive.
Some offspring may be more likely than others to survive and reproduce.
Characteristics that give certain individuals an advantage in surviving and
reproducing might be inherited by their offspring.
e. These characteristics would tend to become more prevalent in the
population in future generations.
3.
A trait or characteristic that promotes success is called an adaptive trait, or an
adaptation. Natural selection acts on genetic variation. Accidental changes in
DNA are called mutations and can give rise to genetic variation among individuals.
If a mutation occurs in a sperm or egg cell, it may be passed on to the next
generation. Most mutations have little effect; some are deadly; others are
beneficial. When organisms reproduce sexually, they mix, or recombine, their
genetic material so that a portion of each parent’s genes contribute to the genes
of the offspring.
4.
Selective pressures from the environment influence adaptation. Closely related
species living in different environments may evolve differently as a result of
23
different selective pressures. Environments change over time and traits that
produce success at one time or location may not do so at another. Natural
selection helps to elaborate and diversify traits that may lead to new species and
new types or organisms.
5.
Evidence of natural selection is all around us. This process of selection conducted
under human direction is termed artificial selection. Many of our domestic pets and
food crops are a result of this process.
6.
Evolution generates biological diversity. Biological diversity, or biodiversity, refers
to the variety of life across all levels of biological organization, including the
diversity of species and their genes, the diversity of populations within a
community, and the diversity of communities within an ecosystem. Scientists have
described about 1.8 million species but estimate that 100 million may exist.
7.
Speciation produces new types of organisms. When populations of the same
species are kept separate, their individuals no longer come in contact, so their
genes no longer mix. If there is no contact, the mutations that occur in one
population cannot spread to the other. Eventually the populations may diverge
enough so that even if they come together again they may not be able to
interbreed and have become different species.
8.
Populations can be separated in many ways. Geographic isolation, or allotropic
speciation – caused by such issues as ice sheet movement, mountain range
building, climate change and similar events – is considered to be the main mode
of species formation. Other mechanisms such as hybridization or different feeding
and mating characteristics can also result in speciation. H. We can infer the history
of life’s diversification by comparing organisms. Scientists represent the history of
divergence on diagrams called phylogenic trees. They illustrate hypotheses of
how divergence took place by looking at similarities among genes or external
characteristics of organisms. By mapping traits such as flights, swimming, or
vocalization on the trees according to which organisms possess them, biologists
can infer evolutionary histories.
9.
The fossil record teaches us about life’s long history. Hard parts of organisms are
often preserved after death when sediments are compressed into rock and
minerals replace the organic material, leaving behind a fossil. Dating these
sediments allows scientists to produce a fossil record. The fossil record shows an
evolution of life on Earth over a period of at least 3.5 billion years with a generally
increasing number of species over time. 3. The species living today are a small
fraction of those that ever existed, many of which disappeared during episodes of
mass extinction.
10. Speciation
and extinction together determine Earth’s biodiversity. The
disappearance of a species is called extinction. The fossil record indicates an
24
average existence of a species on Earth to be 1-10 million years. Human impact
appears to be speeding up extinctions.
11. Some species are more vulnerable to extinction than others. Generally, extinction
occurs when environmental conditions change rapidly or severely enough that a
species cannot genetically adapt to the change. Some species are vulnerable
because they are endemic, occurring in only a single place on the planet.
12. Earth has seen several episodes of mass extinction. There have been five mass
extinction events at widely spaced intervals in Earth’s history. Each wiped out
anywhere from 50 to 95% of Earth’s species each time. The best known of these
occurred 65 million years ago and brought an end to the dinosaurs, but it was not
the largest.
13. The sixth mass extinction is upon us. Many biologists conclude that human
activities have caused an extinction rate that is 100-1,000 times greater than the
historic background rate. Amphibians, such as the golden toad, are disappearing
at a higher rate than other organisms, with 170 species having disappeared in the
last few decades and 30% of their species in danger of extinction.
II.
Levels of Ecological Organization
14. Ecology is the study of interactions among organisms and between organisms and
their environments. We study ecology at several levels. Life occurs in a hierarchy
of levels, from the atoms, molecules, and cells up through the biosphere, which is
the cumulative total of living things on Earth and the areas they inhabit. At the level
of the organism, ecology describes the relationships between the organism and
its physical environment.
Population ecology examines the dynamics of
population change and the factors that affect its distribution and abundance.
15. Communities are made up of multiple interacting species that live in the same
area. Community ecology focuses on species diversity and interactions among
species. 5. Ecosystems encompass communities and the abiotic (nonliving)
material, and forces with which their members interact. Ecosystem ecology
reveals patterns, such as the flows of energy and nutrients, by studying living and
non-living components of systems.
16. Each organism has habitat needs. The specific environment in which an organism
lives is its habitat, which consists of living and non-living elements around it. Each
organism thrives in certain habitats and not others, leading to non-random
patterns of habitat use. Mobile organisms can choose where to live by habitat
selection. For non-mobile organisms whose young disperse and settle passively,
habitat uses result from success in some and failures in others. The habitat needs
of many organisms often conflict with those of humans who want to alter or
develop habitats for human use.
25
A species’ niche reflects
its use of resources and its functional role in a community. Species with very
specific requirements are said to be specialists. Those with broad tolerances, able
to use a wide array of habitats or resources, are generalists.
17. Niche and specialization are key concepts in ecology.
III.
Population Ecology
18. Populations exhibit characteristics that help predict their dynamics. Population
size is the number of individual organisms present at a given time. Population
density is the number of individuals in a population, per unit area. This is often the
major consideration for success or failure of mating or food competition.
Population distribution, or population dispersion, is the spatial arrangement of
organisms within a particular area. Ecologists define three types: random, uniform,
and clumped. A population’s sex ratio is its proportion of males to females. Age
distribution, or age structure, describes the relative numbers of organisms of each
age within a population. Birth and death rates measure the number of births and
deaths per 1,000 individuals for a given time period. The likelihood of death varies
with age; this can be graphically shown in survivorship curves.
19. Populations may grow, shrink, or remain stable. Demographers, scientists who
study human populations, use mathematical concepts to study population
changes. Population growth or decline is determined by four factors: births, deaths,
immigration into an area, and emigration away from an area. The natural rate of
population growth is determined by subtracting the death rate from the birth rate.
The population growth rate equals the crude birth rate plus the immigration rate,
minus the crude death rate plus the emigration rate.
20. Unregulated populations increase by exponential growth. When a population
increases by a fixed percentage each year, it is said to undergo exponential
growth.
21. Limiting factors restrain population growth. Every population is eventually
contained by limiting factors, which are physical, chemical, and biological
characteristics of the environment. The interaction of the limiting factors
determines the carrying capacity. The logistic growth curve, an S-shaped curve,
shows a population that increases sharply at first and then levels off as it is
affected by limiting factors.
22. The influence of some factors on population depends on population density. The
influence of density-dependent factors waxes and wanes according to population
density. Density-independent factors are not affected by population density.
23. Carrying capacities can change. Limiting factors are diverse and complex, and
help keep population levels below carrying capacity. Some organisms can alter
26
their environment to reduce environmental resistance and increase carrying
capacity. Humans have appropriated immense proportions ofthe planet’s
resources and in the process have reduced the carrying capacities for many other
organisms.
24. Reproductive strategies vary among species. Species that devote large amounts
of energy and resources to caring for a few offspring are said to be K-selected,
because their populations tend to stabilize over time at or near their carrying
capacity. Species that are r-selected have high biotic potential and devote their
energy and resources to producing as many offspring as possible in a relatively
short time. K is an abbreviation for carrying capacity, and species that are Kselected speies are ones that tend to stabilize over time at or near the carrying
capacity. Changes in populations influence the composition of communities.
IV.
Species Interactions
25. Competition can occur when resources are limited. Competitive interactions can
take place among members of the same species (intraspecific competition), or
among members of two or more different species (interspecific competition).
Competitive exclusion occurs when one species excludes the other from resource
use entirely. Competing species that live side-by-side at a certain ratio of
population sizes may reach a stable equilibrium point—species coexistence.
Coexisting species that use the same resources tend to minimize competition by
using only a portion of the total array of resources—their niche, or ecological role
in the community—that they are capable of using.
a. The full niche of a species is called its fundamental niche.
b. An individual that plays only part of its role because of competition or other
species interactions is said to be displaying a realized niche.
26. Over time, competing species may evolve to use slightly different resources or to
use their shared resources in different ways; this is resource partitioning.
Because species limit their resource use, over time, character displacement may
occur as they evolve physical characteristics that reflect their reliance on a
particular portion of the resource.
27. Several types of interactions are exploitative. Exploitation occurs when one
member of an interaction exploits another for its own gain.
28. Predators kill and consume prey. Predation is the process by which an individual
of one species, predator, hunts, captures, kills, and consumes an individual of
another species, its prey. Predation can sometimes drive population dynamics,
causing cycles in population sizes. Predation also has evolutionary ramifications:
More adept predators will leave more and healthier offspring, leading to the
27
evolution of adaptations that make them better hunters. The same selective
pressure acts on prey species that evolve defenses against being eaten.
29. Parasites exploit living hosts. Parasitism is a relationship in which one organism,
the parasite, depends on another, the host, for nourishment or some other benefit
while simultaneously doing the host harm. Parasitism usually does not result in an
organism’s immediate death. Many parasites live in close contact with their hosts,
such as disease pathogens, tapeworms, ticks, and lamprey. Other types of
parasites are free-living and come into contact with their hosts only infrequently
(e.g., nest parasites such as cuckoos and cowbirds). Some parasites cause little
harm, but others may kill their hosts to survive, called parasitoids. Hosts and
parasites can become locked in a duel of escalating adaptations called the
evolutionary arms race, resulting in coevolution.
30. Herbivores exploit plants. Herbivory occurs when animals feed on the tissues of
plants. Herbivory does not kill the plant, but can affect growth and reproducti on.
31. Mutualists help one another. Mutualism is a relationship in which two or more
species benefit from interacting with one another. Many mutualistic
relationships—like many parasitic relationships—occur between organisms that
live in close physical contact; thisis called symbiosis. Free-living organisms such
as bees and flowers also engage in mutualism in the process of pollination.
32. Some interactions have no effect on some participants. Amensalism is a
relationship in which one organism is harmed and the other is unaffected.
Commensalism occurs when one organism benefits and the other is unaffected.
V.
Ecological Communities
33. Energy passes among trophic levels. As organisms feed on one another, energy
moves through the community, from one rank in the feeding hierarchy, or trophic
level, to another. Producers, or autotrophs (―self-feeders), comprise the first
trophic level.
34. Producers include terrestrial green plants, cyanobacteria, and algae, and all of
them capture solar energy and use photosynthesis to produce sugars. The
chemosynthetic bacteria of hot springs and deep-sea hydrothermal vents use
geothermal energy in a similar way to produce food.
35. The second level consists of organisms that consume producers (e.g., deer and
grasshoppers) are known as primary consumers. i. Most of them consume plants
and are called herbivores. Examples include deer and grasshoppers.
36. The third level consists of secondary consumers, which prey on primary
consumers. Wolves preying on deer are an example of secondary consumers.
28
37. Predators that feed at higher trophic levels are known as tertiary consumers. An
example of this is hawks that eat rodents that have eaten grasshoppers.
Secondary and tertiary consumers are carnivores because they eat animals.
Animals that eat both plant and animal food are omnivores. Detritivores and
decomposers consume nonliving organic matter.
38. Energy, biomass, and numbers decrease at higher trophic levels. At each trophic
level, most of the energy that organisms use is lost through respiration. The first
trophic level (producers) contains a large amount of energy, while the second
(primary consumers) contains less energy—only that amount gained from
consuming producers. The third trophic level (secondary consumers) contains still
less energy, and higher trophic levels (tertiary consumers) contain the least. A
general rule of thumb is that each trophic level contains just 10% of the energy of
the trophic level below it, although the actual proportion can vary greatly.
39. This pattern can be visualized as a pyramid, and also tends to hold for the
numbers of organisms at each trophic level, with fewer organisms existing at
higher trophic levels than at lower trophic levels. This same pyramid-like
relationship also often holds true for biomass: the collective mass of living matter
in a given place and time.
40. Humans can decrease their ecological footprint by eating lower on the pyramid—
choosing vegetarianism or reducing meat consumption that takes more energy
from the trophic pyramid than a plant-centered diet would.
41. Food webs show feeding relationships and energy flow. As energy is transferred
from species on lower trophic levels to species on higher trophic levels, it is said
to pass up a food chain, a linear series of feeding relationships. A food web is a
visual map of energy flow, showing the many paths by which energy passes
among organisms as they consume one another.
42. Some organisms play bigger roles in communities than others. A keystone species
is a species that has a particularly strong or far- reaching impact. Large-bodied
secondary or tertiary consumers are often considered keystone species.
Predators at high trophic levels can promote populations of organisms at low
trophic levels by keeping species at intermediate trophic levels in check. This is
called the trophic cascade. Some species attain keystone species status not
through what they eat, but by physically modifying the environment.
43. Communities respond to disturbance in different ways. Human activities are
among the major forces of disturbance in ecological communities worldwide. A
community that resists change and remains stable despite disturbance is said to
show resistance to the disturbance. Alternatively, a community may show
resilience, meaning that it changes in response to disturbance but later returns to
29
its original state. A community may be modified by disturbance permanently and
may never return to its original state.
44. Succession follows severe disturbance. If a disturbance is severe enough to
eliminate all or most of the species in a community, the affected site will undergo
a somewhat predictable series of changes that ecologists call succession.
45. Primary succession follows a disturbance so severe that no vegetation or soil life
remains from the community that previously occupied the site. In primary
succession, a biotic community is built essentially from scratch.
46. Secondary succession begins when a disturbance dramatically alters an existing
community but does not destroy all living things or all organic matter in the soil. At
terrestrial sites, primary succession takes place after a bare expanse of rock, sand,
or sediment becomes newly exposed. Species that arrive first and colonize the
new substrate are referred to as pioneer species. i. Pioneer species, such as
lichens, are the first to arrive. ii. Lichens secrete acid, starting the process of soil
formation. iii. New, larger organisms arrive, establish themselves, and pave the
way for more new species, where eventually a climax community becomes
established.
47. In the traditional view of succession, the transitions between stages of succession
eventually lead to a climax community, which remains in place with little
modification until some disturbance restarts succession.
48. Communities may undergo shifts. Today, ecologists recognize that the dynamics
of community change are far more variable and less predictable than originally
thought. In addition, climax communities are not determined solely by climate, but
rather may vary with soil conditions and other factors from one time or place to
another. Moreover, once a community is disturbed and changes are set in
motion, there is no guarantee that the community will ever return to its original
state. A phase shift or regime shift is where the overall character of the community
fundamentally changes.
Activity
1. Read and study – Republic Act 110338 (Expanded National Integrated Protected
Areas System)
2. Name at least three (3) terrestrial, three (3) inland wetland, and three (3) coastal
and marine Protected Areas (PAs) in the Philippines. Prepare a simple matrix by
identifying the types of ecosystems and indicator species present in the identified
PAs.
30
Module 05
Population Principles and Demography
Time Frame: 2 Weeks (Week 10-11)
Overview:
Lesson 1: General principles of population growth
1. Biotic potential
2. Exponential population growth
3. Environmental resistance
4. Ecosystem carrying capacity
Lesson 2: Demography: Principles governing human populations
1. Total fertility rate
2. Rate of natural increase
3. Migration patterns and growth rates
4. Population age structures
5. Demographic transitions
6. Environmental factors
Case study: Population growth in China
7. Future world population trends
8. Cutting global population growth
Objectives:
After successfully completing this module, students should be able to:
1. Explain the concepts of population and demography.
2. Define the different demographical characteristics of a population and explain how
they relate to each other.
3. Explain the four factors that produce changes in population size.
4. Identify Thomas Malthus, relate his ideas on human population growth, and
explain why he may or may not have been wrong.
5. Explain why it is impossible to precisely determine how many people Earth can
support—that is, Earth’s carrying capacity for humans.
6. Define demographics and describe the demographic transition.
7. Relate total fertility rates to each of the following: cultural values, social and
economic status of women, availability of family planning services, and
government policies.
8. Explain the link between education and total fertility rates.
9. Explain how highly developed and developing countries differ in population
characteristics such as infant mortality rate, total fertility rate, replacement-level
fertility, and age structure.
31
Lesson 1. General Principles of Population Growth
1. Biotic Potential
Individuals of a given species are part of a larger organization called a population.
Populations exhibit characteristics that are distinct from those of the individuals in them.
Some of the features characteristic of populations but not of individuals are birth and
death rates, growth rates, and age structure. Studying populations of nonhuman species
provides insight into some of the processes that affect the growth of human populations.
Understanding human population change is important because the size of the human
population is central to most of Earth’s environmental problems and their solutions.
Biotic Potential is the general study of population changes. One of the most important
properties of living things is that their abundances change over time and space. This is
as true for our own species as it is for all others, including those that directly or indirectly
affect our lives—for example, by providing our food, or materials for our shelter, or causing
diseases and other problems— and those that we just like having around us or knowing
that they exist.
Different species have different biotic potentials (also called intrinsic rates of increase).
Several factors influence the biotic potential of a species:
a.
b.
c.
d.
the age at which reproduction begins;
the fraction of the life span during which an individual can reproduce;
the number of reproductive periods per lifetime; and
the number of offspring produced during each period of reproduction.
Significant differences in biotic potential exist between species – many large mammals,
like humans or elephants, will only produce one offspring per year and some small
organisms, like insects, will produce thousands of offspring per year. Organisms do not
tend to fulfill their biotic potential because most species do not live under ideal
environmental conditions. At some point, population growth will be hindered by predators,
disease, changes in environment, a lack of available food, or a combination of these
factors. These factors, called life history characteristics, determine whether a particular
species has a large or a small biotic potential.
Generally, larger organisms, such as blue whales and elephants, have the smallest biotic
potentials, whereas microorganisms have the greatest biotic potentials. Under ideal
conditions (that is, in an environment with unlimited resources), certain bacteria reproduce
by dividing in half every 30 minutes. At this rate of growth, a single bacterium increases
to a population of more than 1 million in just 10 hours and exceeds 1 billion in 15 hours.
If you plot bacterial population numbers versus time, the graph takes on the characteristic
32
J shape of exponential population growth (Figure C-1).
When a population grows exponentially, the larger the
population gets, the faster it grows. Regardless of
species, whenever a population grows at its biotic
potential, population size plotted versus time gives the
same J-shaped curve. The only variable is time. It may
take longer for a dolphin population than for a bacterial
population to reach a certain size dolphin do not
reproduce as rapidly as bacteria, but both populations
will always increase exponentially as long as their
growth rates remain constant.
Figure: C-1
(from: Visualizing Environmental Science, Berg 4th Ed. 2014)
2. Exponential Population Growth
In theory, any kind of organism could take over the Earth just by reproducing. For instance,
imagine that we started with a single pair of male and female rabbits. If these rabbits and
their descendants reproduced at top speed ("like bunnies") for 7 years, without any deaths,
we would have enough rabbits to cover the entire state of Rhode Island. And that's not
even so impressive – if we used E. coli bacteria instead, we could start with just one
bacterium and have enough bacteria to cover the Earth with a 1-foot layer in just 36 hours.
As you've probably noticed, there isn't a 1-foot layer of bacteria covering the entire Earth,
nor have bunnies taken possession of Rhode Island. Why, then, don't we see these
populations getting as big as they theoretically could? E. coli, rabbits, and all living
organisms need specific resources, such as nutrients and suitable environments, in order
to survive and reproduce. These resources are limited, and a population can only reach
a size that match the availability of resources in its local environment.
Population ecologists use a variety of mathematical methods to model population
dynamics (how populations change in size and composition over time). Some of these
models represent growth without environmental constraints, while others include
"ceilings" determined by limited resources. Mathematical models of populations can be
used to accurately describe changes occurring in a population and, importantly, to predict
future changes.
33
Modeling population growth rates
To understand the different models that are used to represent population dynamics, let's
start by looking at a general equation for the population growth rate (change in number of
individuals in a population over time):
𝑑𝑁
= 𝑟𝑁
𝑑𝑇
In this equation, dN/dT is the growth rate of the population in a given instant, N is
population size, T is time, and r is the per capita rate of increase –that is, how quickly the
population grows per individual already in the population.
If we assume no movement of individuals into or out of the population, r is just a function
of birth and death rates.
The equation above is very general, and we can make more specific forms of it to describe
two different kinds of growth models: exponential and logistic.
• When the per capita rate of increase (r) takes the same positive value regardless of
the population size, then we get exponential growth.
• When the per capita rate of increase (r) decreases as the population increases towards
a maximum limit, then we get logistic growth.
i. Exponential growth
Bacteria grown in the lab provide an excellent example of exponential growth.
In exponential growth, the population’s growth rate increases over time, in proportion to
the size of the population.
Let’s take a look at how this works. Bacteria reproduce by binary fission (splitting in half),
and the time between divisions is about an hour for many bacterial species. To see how
this exponential growth, let's start by placing 1,000 bacteria in a flask with an unlimited
supply of nutrients. After 1 hour: Each bacterium will divide, yielding 2,000 bacteria (an
increase of 1000 bacteria). After 2 hours: Each of the 2,000 bacteria will divide,
producing 4,000 (an
increase
of 2,000 bacteria).
After 3 hours:
Each
of
the 4,000 bacteria will divide, producing 8,000 (an increase of 400040004000 bacteria).
34
The key concept of exponential growth is that the
population growth rate —the number of organisms
added in each generation— increases as the
population gets larger. And the results can be dramatic:
after 1 day (24 cycles of division), our bacterial
population
would
have
grown
from 1000 to
over 16 billion! When population size, N, is plotted
over time, a J-shaped growth curve is created.
How do we model the exponential growth of a
population?
As we mentioned briefly above, we get
Figure C-2.
exponential growth when r (the per capita rate of
increase) for our population is positive and constant. While any positive, constant r can
lead to exponential growth, you will often see exponential growth represented with
an r of rmax.
rmax is the maximum per capita rate of increase for a particular species under ideal
conditions, and it varies from species to species. For instance, bacteria can reproduce
much faster than humans, and would have a higher maximum per capita rate of increase.
The maximum population growth rate for a species, sometimes called its biotic potential,
is expressed in the following equation:
𝑑𝑁
= 𝑟𝑚𝑎𝑥 𝑁
𝑑𝑇
ii. Logistic growth
Exponential growth is not a very sustainable state of
affairs, since it depends on infinite amounts of
resources (which tend not to exist in the real world).
Exponential growth may happen for a while, if there
are few individuals and many resources. But when
the number of individuals gets large enough,
resources start to get used up, slowing the growth
rate. Eventually, the growth rate will plateau, or level
off, making an S-shaped curve. The population size
at which it levels off, which represents the maximum
population size a particular environment can support,
is called the carrying capacity, or K.
35
Figure C-3.
We can mathematically model logistic growth by modifying our equation for exponential
growth, using an r (per capita growth rate) that depends on population size (N) and how
close it is to carrying capacity (K). Assuming that the population has a base growth rate
of rmax when it is very small, we can write the following equation:
𝑑𝑁
(𝐾 − 𝑁)
= 𝑟𝑚𝑎𝑥
𝑁
𝑑𝑇
𝐾
At any given point in time during a population's growth, the expression K−N, tells us how
many more individuals can be added to the population before it hits carrying capacity.
(K – N)/K, then, is the fraction of the carrying capacity that has not yet been “used up.”
The more carrying capacity that has been used up, the more the (K – N)/K term will reduce
the growth rate.
When the population is tiny, N is very small compared to K. The (K - N)/K term becomes
approximately (K/K) or 1, giving us back the exponential equation. This fits with our graph
above: the population grows near-exponentially at first, but levels off more and more as it
approaches K.
One of the first people to recognize that the human population can’t increase indefinitely
was Thomas Malthus (1766–1834), a British economist. He pointed out that human
population growth is not al- ways desirable—a view contrary to the beliefs of his day and
to those of many people even today. Noting that human population can increase faster
than its food supply, he warned that the inevitable consequences of population growth
would be famine, disease, and war. Since Malthus’s time, the human population has
increased from about 1 billion to 7 billion.
On the surface, it seems that Malthus was wrong. Our population has grown dramatically
because geographic expansion and scientific advances have allowed food production to
keep pace with population growth. Malthus’s ideas may ultimately be proved correct,
however, because we don’t know whether this increased food production is sustainable.
Have we achieved this increase in food production at the environmental cost of reducing
the planet’s ability to meet the needs of future populations? Many economists suggest
that market forces and future technologies will help us prevent resource depletion such
as soil degradation and over- fishing in the ocean. But the truth is that we still do not know
if Malthus was wrong or right.
Our world population was 7 billion in late 2011, an increase of about 95 million from 2010.
This increase was not due to a rise in the birth rate (b), although high birth rates are a
serious problem in many countries. In fact, the world birth rate has declined slightly during
the past 200 years. The population growth is due instead to a dramatic decrease in the
death rate (d), which has occurred primarily because greater food production, better
36
medical care, and improvements in water quality and sanitation practices have increased
life expectancy for a great majority of the global population.
3. Environmental Resistance
Certain populations—particularly those of bacteria, protists, and certain insects—may
exhibit exponential population growth for a short period. However, organisms don’t
reproduce indefinitely at their biotic potentials because the environment sets limits, which
are collectively called environmental resistance.
Thus, the environment controls population size: As the population increases, so does
environmental resistance, which limits population growth.
There two kinds of Environmental Resistance
a. Density Dependent Factor
Let's start off with an example. Imagine a population of organisms—let's say, deer—with
access to a fixed, constant amount of food. When the population is small, the limited
amount of food will be plenty for everyone. But, when the population gets large enough,
the limited amount of food may no longer be sufficient, leading to competition among the
deer. Because of the competition, some deer may die of starvation or fail to have offspring,
decreasing the per capita—per individual—growth rate and causing population size to
plateau or shrink.
In this scenario, competition for food is a density-dependent limiting factor. In general, we
define density-dependent limiting factors as factors that affect the per capita growth rate
of a population differently depending on how dense the population already is. Most
density-dependent factors make the per capita growth rate go down as the population
increases. This is an example of negative feedback that limits population growth.
Density-dependent limiting factors can lead to a logistic pattern of growth, in which a
population's size levels off at an environmentally determined maximum called
the carrying capacity. Sometimes this is a smooth process; in other cases, though, the
population may overshoot carrying capacity and be brought back down by densitydependent factors
Density-dependent limiting factors tend to be biotic—living organism-related—as
opposed to physical features of the environment. Some common examples of densitydependent limiting factors include:
37
Competition within the population. When a population reaches a high density,
there are more individuals trying to use the same quantity of resources. This can
lead to competition for food, water, shelter, mates, light, and other resources
needed for survival and reproduction.
ii. Predation. Higher-density populations may attract predators who wouldn’t bother
with a sparser population. When these predators eat individuals from the
population, they decrease its numbers but may increase their own. This can
produce interesting, cyclical patterns.
iii. Disease and parasites. Disease is more likely to break out and result in deaths
when more individuals are living together in the same place. Parasites are also
more likely to spread under these conditions.
iv. Waste accumulation. High population densities can lead to the accumulation of
harmful waste products that kill individuals or impair reproduction, reducing the
population’s growth.
i.
Density-dependent regulation can also take the form of behavioral or physiological
changes in the organisms that make up the population. For example, rodents called
lemmings respond to high population density by emigrating in groups in search of a new,
less crowded place to live. This process has been misinterpreted as a mass suicide of
sorts in popular culture because the lemmings sometimes die while trying to cross bodies
of water.
b. Density-independent limiting factors
The second group of limiting factors consists of density-independent limiting factors that
affect per capita growth rate independent of how dense the population is.
As an example, let's consider a wildfire that breaks out in a forest where deer live. The
fire will kill any unlucky deer that are present, regardless of population size. An individual
deer's chance of dying doesn't depend at all on how many other deer are around. Densityindependent limiting factors often take the form of natural disasters, severe weather, and
pollution.
Unlike density-dependent limiting factors, density-independent limiting factors alone can’t
keep a population at constant levels. That’s because their strength doesn’t depend on the
size of the population, so they don’t make a "correction" when the population size gets
too large. Instead, they may lead to erratic, abrupt shifts in population size. Small
populations may be at risk of getting wiped out by sporadic, density-independent events.
Over longer periods, environmental resistance may eventually reduce the rate of
population growth to nearly zero. This leveling out occurs at or near the environment’s
carrying capacity (K).
38
4. Ecological Carrying Capacity
In nature, carrying capacity is dynamic and
changes in response to environmental changes. An
extended drought, for example, might decrease the
amount of vegetation growing in an area, and this
change, in turn, would lower the carrying capacity
for deer and other herbivores in that environment.
G. F. Gause, a Russian ecologist who conducted
experiments in the 1930s, grew a population of
Paramecium in a test tube. He supplied a limited
amount of food daily and replenished the media to
eliminate the buildup of wastes. Under these
conditions, the population increased exponentially
at first, but then its growth rate declined to zero, and
the population size leveled off.
Figure C-4.
When a population influenced by environmental resistance is graphed over a long period,
the curve has an S shape. The curve shows the population’s initial exponential increase
(note the curve’s J shape at the start, when environmental resistance is low). Then the
population size levels out as it approaches the carrying capacity of the environment. The
rate of population growth is proportional to the amount of existing resources, and
competition leads to limited population growth. Although the S curve is an
oversimplification of how most populations change over time, it fits some populations
studied in the laboratory, as well as a few studied in nature.
A population rarely stabilizes at K (carrying capacity), as shown in Figure 7.4, but its size
may temporarily rise higher than K. It will then drop back to, or below, the carrying
capacity. Sometimes a population that overshoots K will experience a population crash,
an abrupt decline from high to low population density when resources are exhausted.
Such an abrupt change is commonly observed in bacterial cultures, zooplankton, and
other populations whose resources are exhausted.
Apply those concepts to the human population.
Figure C-5 shows the increase in human
population. On our finite planet the human
population will eventually be limited by some
factor or combination of factors. We can group
limiting factors into those that affect a
population during the year in which they
become limiting (short-term factors), those
whose effects are apparent after one year but
before ten years (intermediate-term factors),
and those whose effects are not apparent for
39
Figure C-5 .
ten years (long-term factors). Some factors fit into more than one category, having, say,
both short-term and intermediate-term effects.
An important short-term factor is the disruption of food distribution in a country, commonly
caused by drought or by a shortage of energy for transporting food.
Intermediate-term factors include desertification; dispersal of certain pollutants, such as
toxic metals, into waters and fisheries; disruption in the supply of non-renewable
resources, such as rare metals used in making steel alloys for transportation machinery;
and a decrease in the supply of firewood or other fuels for heating and cooking.
Long-term factors include soil erosion, a decline in groundwater supplies, and climate
change. A decline in resources available per person suggests that we may already have
exceeded Earth’s long-term human carrying capacity.
Since the rise of the modern environmental movement in the second half of the 20th
century, much attention has focused on estimating the human carrying capacity of Earth—
the total number of people that our planet could support indefinitely. This estimation has
typically involved three methods. One method, which we have already discussed, is to
simply extrapolate from past growth, assuming that the population will follow an S-shaped
logistic growth curve and gradually level off.
The second method can be referred to as the packing- problem approach. This method
simply considers how many people might be packed onto Earth, not taking into sufficient
account the need for land and oceans to provide food, water, energy, construction
materials, the need to maintain biological diversity, and the human need for scenic beauty.
This approach, which could also be called the standing-room-only approach, has led to
very high estimates of the total number of people that might occupy Earth—as many as
50 billion.
More recently, a philosophical movement has developed at the other extreme. Known as
deep ecology, this third method makes sustaining the biosphere the primary moral
imperative. Its proponents argue that the whole Earth is necessary to sustain life, and
therefore everything else must be sacrificed to the goal of sustaining the biosphere.
People are considered active agents of destruction of the biosphere, and therefore the
total number of people should be greatly reduced. Estimates based on this rationale for
the desirable number of people vary greatly, from a few million up.
Between the packing-problem approach and the deep-ecology approach are a number of
options. It is possible to set goals in between these extremes, but each of these goals is
a value judgment, again reminding us of one of this book’s themes: science and values.
What constitutes a desirable quality of life is a value judgment. The perception of what is
desirable will depend in part on what we are used to, and this varies greatly.
40
Moreover, what quality of life is possible depends not just on the amount of space
available but also on technology, which in turn is affected by science. Scientific
understanding also tells us what is required to meet each quality-of-life level. The options
vary. If all the people of the world were to live at the same level as those of the United
States, with our high resource use, then the carrying capacity would be comparatively
low. If all the people of the world were to live at the level of those in Bangladesh, with all
of its risks as well as its poverty and its heavy drain on biological diversity and scenic
beauty, the carrying capacity would be much higher.
In summary, the acceptable carrying capacity is not simply a scientific issue; it is an issue
combining science and values, within which science plays two roles. First, by leading to
new knowledge, which in turn leads to new technology, it makes possible both a greater
impact per individual on Earth’s resources and a higher density of hu- man beings.
Second, scientific methods can be used to forecast a probable carrying capacity once a
goal for the average quality of life, in terms of human values, is chosen. In this second
use, science can tell us the implications of our value judgments, but it cannot provide
those value judgments.
Lesson 2: Demography: Principles governing human populations
Demography (derived from the Greek words demos, people, and graphein, to write or to
measure) encompasses vital statistics about people, such as births, deaths, and where
they live, as well as total population size. In this section we will investigate ways to
measure and describe human populations and discuss demographic factors that
contribute to population growth.
There is an ultimate carrying capacity for
the human population. Eventually, limiting
factors will cause human populations to
stabilize. However, unlike other kinds of
organisms, humans are also influenced
by social, political, economic, and ethical
factors. We have accumulated knowledge
that allows us to predict the future. We
can make conscious decisions based on
the likely course of events and adjust our
lives accordingly. Part of our knowledge is
Fig. C – 6 Total fertility rates for the whole world have fallen by
the certainty that as populations continue
more than half over the past 50 years. Much of this dramatic
to increase, death rates and birth rates will change has occurred in China and India. Progress has lagged in
sub-Saharan Africa,
become equal. This can happen by allowing but by 2050 the world average should be approaching the
the death rate to rise or by choosing to limit the birth rate. Controlling human population
would seem to be a simple process. Once people understand that lowering the birth rate
is more humane than allowing the death rate to rise, they should make the “correct”
decision and control their birth rates; however, it is not quite that simple.
41
1. TOTAL FERTILITY RATE
The most important determinant of the rate at which human populations grow is related
to how many women in the population are having children and the number of children
each woman will have. The total fertility rate of a population is the number of children born
per woman in her lifetime. A total fertility rate of 2.1 is known as replacement fertility, since
parents produce 2 children who will replace the parents when they die. Eventually, if the
total fertility rate is maintained at 2.1, population growth will stabilize. A rate of 2.1 is used
rather than 2.0 because some children do not live very long after birth and therefore will
not contribute to the population for very long. When a population is not growing, and the
number of births equals the number of deaths, it is said to exhibit zero population growth.
For several reasons, however, a total fertility rate of 2.1 will not necessarily immediately
result in a stable population with zero growth. First, the death rate may fall as living
conditions improve and people live longer. If the death rate falls faster than the birth rate,
there will still be an increase in the population even though it is reproducing at the
replacement rate
Fertility has declined in recent decades. Fecundity is the physical ability to reproduce,
whereas fertility is the actual production of offspring. A common statistic used to describe
fertility in a population is the crude birth rate, the number of births in a year per thousand
persons. It is statistically “crude” in the sense that it is not adjusted for population
characteristics, such as the number of women of reproductive age.
The total fertility rate, the average number of children per woman, is sometimes easier to
remember. In the last 50 years, fertility rates have declined dramatically almost
everywhere except sub-Saharan Africa, where poverty and other factors remain
persistently entrenched. In 1975 the average family in Mexico, for instance, had 7
children. By 2017, however, the average Mexican woman had only 2.17 children.
Similarly, in Iran total fertility fell from 6.5 in 1975 to 1.8 in 2017. According to the World
Health Organization, the global average fertility rate is 2.45, and about half the world’s
192 countries are now at or below a replacement rate of 2.1 children per couple.
This decline cuts across economic regions. Bangladesh, still one of the poorest countries,
reduced its fertility rate from 6.9 in 1980 to only 2.1 children per woman in 2017. China’s
one-child-per-family policy decreased the fertility rate from 6 in 1970 to 1.6 in 2017. This
program was remarkably successful in reducing population growth, but China decided to
end it in 2015. Despite these dramatic declines, population growth will continue because
much of the world’s population is very young. Brazil, for example, now has a fertility rate
of only 1.8 children per woman. But 26 percent of its population is under 14, so the
population will continue to grow for some decades. Demographers call this population
momentum. Since the 1960s, which saw the fastest growth and shortest population
doubling times ever, many people concerned about resource availability have been eager
42
to see zero population growth (ZPG). Zero growth occurs when number of deaths exactly
equals number of births plus immigration.
Ironically, now that many populations are falling below replacement levels, it is emerging
that economists are unable to accommodate zero population growth. States and
businesses need constantly growing numbers of workers, and especially consumers, to
maintain economic growth. One of the strong forces promoting China’s abandonment of
the one-child policy was this economic growth imperative. It remains unclear how these
contrasting priorities of environmental conservation, economic growth, and social stability
will be resolved.
Fertility is influenced by culture
A number of social and economic pressures affect decisions about family size, which in
turn affect the population at large. Factors that increase people’s desires to have babies
are called pronatalist pressures. Raising a family may be the most enjoyable and
rewarding part of many people’s lives. Children can be a source of pleasure, pride, and
comfort. They may be the only source of support for elderly parents in countries without
a social security system. Where infant mortality rates are high, couples may need to have
many children to ensure that at least a few will survive to take care of them when they are
old. Where there is little opportunity for upward mobility, children give status in society,
express parental creativity, and provide a sense of continuity and accomplishment
otherwise missing from life.
Often children are valuable to the family not only for future income but even more as a
source of current income and help with household chores. In much of the developing
world, small children tend domestic animals and younger siblings, fetch
water, gather firewood, help grow crops, or sell things in the marketplace
Society also has a need to replace members who die or become incapacitated. This need
often is codified in cultural or religious values that encourage bearing and raising children.
Some societies look upon families with few or no children with pity or contempt, and for
them the idea of deliberately controlling fertility may be shocking, even taboo. Women
who are pregnant or have small children have special status and protection. Boys
frequently are more valued than girls because they carry on the family name and are
expected to support their parents in old age. Couples may have more children than they
desire in an attempt to produce a son who lives to maturity.
Male pride often is linked to having as many children as possible. In Niger and Cameroon,
for example, men on average want 12.6 and 11.2 children, respectively. Women in these
countries want only 5 or 6 on average. Even though a woman might desire fewer children,
however, she may have few choices and little control over her own fertility. In many
societies a woman has no status outside of her role as wife and mother. Yet without
children, she may have no source of support in her old age.
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Education and income affect the desire for children
Higher education and personal freedom for women often result in decisions to limit
childbearing. When women have opportunities to earn a salary, they are less likely to stay
home and have many children. Not only do many women find the challenge and variety
of a career attractive, but the money that they earn outside the home becomes an
important part of the family budget. Also, educated women are more likely to have the
family status to make their own decisions about childbearing.
In less-developed countries, where feeding and clothing children can be a minimal
expense, adding one more child to a family usually doesn’t cost much. By contrast, raising
a child in a developed country can cost hundreds of thousands of dollars, and it can be
hard for parents to afford more than one or two.
Cultural and political factors also influence childbearing. The period between 1910 and
1930 was a time of industrialization and urbanization. Women were getting more
education than ever before and entering the workforce in large numbers. The Great
Depression in the 1930s made it economically difficult for families to have children, and
birth rates were low. The birth rate increased at the beginning of World War II (as it often
does in wartime). A “baby boom” followed World War II, as couples were reunited and
new families started. During this time the government encouraged women to leave their
wartime jobs and stay home. A high birth rate persisted through the times of prosperity
and optimism of the 1950s but began to fall in the 1960s. Part of this decline was caused
by the small number of babies born in the 1930s, which resulted in fewer young adults to
give birth in the 1960s. Part was due to changed perceptions of the ideal family size.
Whereas in the 1950s women typically wanted four children or more, the norm dropped
to one or two (or no) children in the 1970s. A small “echo boom” occurred in the 1980s,
as baby boomers began to have children, but changing economics and attitudes seem to
have altered our view of ideal family size in the United States.
2. RATE OF NATURAL INCREASE
Natural increase. Put simply, natural increase is the difference between the numbers of
births and deaths in a population; the rate of natural increase is the difference between
the birthrate and the death rate. Given the fertility and mortality characteristics of
the human species (excluding incidents of catastrophic mortality), the range of possible
rates of natural increase is rather narrow. For a nation, it has rarely exceeded 4 percent
per year; the highest known rate for a national population—arising from the conjunction
of a very high birthrate and a quite low death rate—is that experienced in Kenya during
the 1980s, in which the natural increase of the population approximated 4.1 percent per
annum. Rates of natural increase in other developing countries generally are lower; these
countries averaged about 2.5 percent per annum during the same period. Meanwhile the
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rates of natural increase in industrialized countries are very low: the highest is
approximately 1 percent, most are in the neighborhood of several tenths of 1 percent, and
some are slightly negative (that is, their populations are slowly decreasing).
China has made impressive efforts to feed its people, bring its population growth under
control, and encourage economic growth. Between 1972 and 2007, the country cut its
crude birth rate in half and trimmed its TFR from 5.7 to 1.6 children per woman, compared
to 2.05 in the United States. Despite such drops China is the world’s most populous
country. If current trends continue, China’s population is expected to peak around 2040
and then begin a slow decline. Since 1980, China has moved 350 million people (an
amount greater than the entire U.S. population) from extreme poverty to middle-class
consumers and is likely to double that number by 2010. China also has aliteracy rate of
91% and has boosted life expectancy to 72 years. By 2020, some economists project that
China could become the world’s leading economic power.
In the 1960s, government officials concluded that the only alternative to strict population
control was mass starvation. To achieve a sharp drop in fertility, China established the
most extensive, intrusive, and strict family planning and population control program in the
world. It discourages premarital sex and urges people to delay marriage and limit their
families to one child each. Married couples who pledge to have no more than one child
receive more food, larger pensions, better housing, free health care, salary bonuses, free
school tuition, and preferential employment opportunities for their child. Couples who
break their pledge lose such benefits.
The government also provides married couples with free sterilization, contraceptives, and
abortion. However, reports of forced abortions and other coercive actions have brought
condemnation from the United States and other national governments. In China, there is
a strong preference for male children, because unlike sons, daughters are likely to marry
and leave their parents. A folk saying goes, “Rear a son, and protect yourself in old age.”
Some pregnant Chinese women use ultrasound to determine the gender of their fetus,
and some get an abortion if it is female. The result: a rapidly growing gender imbalance
or “bride shortage” in China’s population, with a projected 30–40 million surplus of men
expected by 2020. Because of this skewed sex ratio, teen-age girls in some parts of rural
China are being kidnapped and sold as brides for single men in other parts of the country.
With fewer children, the average age of China’s population is increasing rapidly. By 2020,
31% of China’s population will be over 60 years old compared to 8% in 2007. This graying
of the Chinese population could lead to a declining work force, higher wages for younger
workers, lack of funds for supporting continuing economic development, and fewer
children and grandchildren to care for the growing number of elderly people. These and
other factors may slow economic growth and lead to some relaxation of China’s one child
population control policy. Some middle-class couples now have more than one child and
pay the fines.
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China also faces serious resource and environmental problems. It has 20% of the world’s
population, but only 7% of the world’s freshwater and cropland, 4% of its forests, and 2%
of its oil. In 2005, China’s deputy minister of the environment summarized the country’s
environmental problems: “Our raw materials are scarce, we don’t have enough land, and
our population is constantly growing. Half of the water in our seven largest rivers is
completely useless. One-third of the urban population is breathing polluted air.”
China’s economy is growing at one of the world’s highest rates as the country undergoes
rapid industrialization. More middle-class Chinese will consume more resources per
person, increasing China’s ecological footprint within its own borders and in other parts
of the world that provide it with resources. This will put a strain on the earth’s natural
capital unless China steers a course toward more sustainable economic development.
Future world population trends
The human population has reached a
turning point. Although our numbers
continue to increase, the world growth rate
(r) has declined slightly over the past
several years, from a peak of 2.2 percent
per year in the mid-1960s to the current
growth rate of 1.2 percent per year.
Population experts at the United Nations
and the World Bank project that the growth
rate will continue to decrease slowly until
zero population growth is attained toward
the end of the 21st century. Exponential
growth of the human population will end,
and the S curve may replace the J curve.
The United Nations periodically publishes
population projections for the 21st century.
The latest (2010) U.N. figures forecast that
the human population will reach 9.3 billion in
the year 2050 (their “medium” projection),
and could range between 8.1 billion (their
“low” projection) and 10.6 billion (their “high”
projection) (Figure C-7). The estimates vary
depending on fertility changes, particularly
Figure C-7.
in less developed countries, because that is
where almost all of the growth will take place. Population projections must be interpreted
with care because they vary depending on what assumptions are made. In projecting that
the world population will be 8.1 billion (their low projection) in the year 2050, U.N.
population experts assume that the average number of children born to each woman in
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all countries will have declined to 1.7 by 2045–2050. The average number of children
born to each woman on Earth is currently 2.5. If the decline to 1.7 doesn’t occur, our
population could be significantly higher. If the average number of children born to each
woman declines to 2.17 in 2045–2050 instead of 1.5, the 2050 population will be 9.3 billion
(the U.N. medium projection).
Small differences in fertility, then, produce large differences in population forecasts.
The main unknown factor in any population growth scenario is Earth’s carrying capacity.
Most published estimates of how many people Earth can support range from 4 billion to
16 billion. For example, in 2004, environmental economists in the Netherlands performed
a detailed analysis of 69 recent studies of Earth’s carrying capacity for humans. Based
on current technology, they estimated that 7.7 billion is the upper limit of human
population that the world can support. Even the low U.N. projection for 2050 exceeds this
value.
These estimates vary widely depending on what assumptions are made about standard
of living, resource consumption, technological innovations, and waste generation. If we
want all people to have a high level of material well-being equivalent to the lifestyles in
highly developed countries, then Earth will support far fewer humans than if everyone
lives just above the subsistence level. Unlike with other organisms, environmental
constraints aren’t the exclusive determinant of Earth’s carrying capacity for humans.
Human choices and values must be factored into the assessment.
Figure C-8 .
What will happen to the human population when it approaches Earth’s carrying capacity?
Optimists suggest that a decrease in the birth rate will stabilize the human population.
Some experts take a more pessimistic view and predict that our ever-expanding numbers
will cause widespread environmental degradation and make Earth uninhabitable for
humans as well as other species (Figure C-8). These population researchers contend that
a massive wave of human suffering and death will occur. This view doesn’t mean we will
47
go extinct as a species, but it projects severe hardship for many people. Some experts
think the human population has already exceeded the carrying capacity of the
environment, a potentially dangerous situation that threatens our long-term survival as a
species.
Cutting global population growth
Dispersal—moving from one place to another— used to be a solution for unsustainable
population growth, but not today. As a species, we humans have expanded our range
throughout Earth, and few habitable areas remain that have the resources to adequately
support a major increase in human population. It is unlikely that death rates will increase
substantially in the foreseeable future. Consequently, global human population will not
stabilize unless birth rates drop. Cultural traditions, women’s social and economic status,
family planning, and government policies all influence total fertility rate (TFR).
Culture and Fertility
The values and norms of a society—what is considered right and important and what is
expected of a person— are all a part of that society’s culture. A society’s culture, which
includes its language, beliefs, and spirituality, exerts a powerful influence over individuals
by controlling behavior. Gender—that is, varying roles men and women are expected to
fill—is an important part of culture. Different societies have different gender expectations.
With respect to fertility and culture, a couple is expected to have the number of children
traditional in their society.
High TFRs are traditional in many cultures. The motivations for having many babies vary
from culture to culture, but a major reason for high TFRs is that infant and child mortality
rates are high. For a society to endure, it must produce enough children who can survive
to reproductive age. If infant and child mortality rates are high, TFRs must be high to
compensate. Although world infant and child mortality rates are decreasing, it will take
longer for culturally embedded fertility levels to decline. Parents must have confidence
that the children they already have will survive before they stop having additional babies.
The Social and Economic Status of Women
Gender inequality exists to varying degrees in most societies: Women don’t have the
same rights, opportunities, or privileges as men. Gender disparities include the lower
political, social, economic, and health status of women compared to men. For example,
more women than men live in poverty, particularly in developing countries. In most
countries, women are not guaranteed equality in legal rights, education, employment and
earnings, or political participation. Because sons are more highly valued than daughters,
girls are often kept at home to work rather than being sent to school.
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In most developing countries, a higher percentage of women are illiterate than men.
However, definite progress has been made in recent years in increasing literacy in both
women and men and in narrowing the gender gap. Fewer young women and men are
illiterate than older women and men within a given country. Worldwide, some 90 million
girls aren’t given the opportunity to receive a primary (elementary school) education.
Laws, customs, and lack of education often limit women to low-skilled, low-paying jobs.
In such societies, marriage is usually the only way for a woman to achieve social influence
and economic security.
Evidence suggests that the single most important factor affecting high TFRs may be the
low status of women in many societies. An effective strategy for reducing population
growth, then, is to improve the social and economic status of women. The average age
at which women marry affects the TFR; in turn, the laws and customs of a given society
affect marriage age. Women who marry are more likely to bear children than women who
don’t marry, and the earlier a woman marries, the more children she is likely to have.
In nearly all societies, women with more education tend to marry later and have fewer
children. Providing women with educational opportunities delays their first childbirth,
thereby reducing the number of childbearing years and increasing the amount of time
between generations. Education provides greater career opportunities and may change
women’s lifetime aspirations. Education increases the probability that women will know
how to control their fertility. It also provides knowledge to improve the health of the
women’s families, which results in a decrease in infant and child mortality.
A study in Kenya showed that 10.9 percent of children born to women with no education
died by age 5, as compared with 7.2 percent of children born to women with a primary
education, and 6.4 percent of children born to women with a secondary education.
Education also increases women’s career options and provides ways of achieving status
besides having babies. Education may also have an indirect effect on TFR. Children who
are educated have a greater chance of improving their living standards, partly because
they have more employment opportunities. Parents who recognize this may be more
willing to invest in the education of a few children than in the birth of many children whom
they can’t afford to educate.
Family Planning Services
Socioeconomic factors may encourage people to want smaller families, but fertility
reduction won’t become a reality without the availability of health and family planning
services. The governments of most countries recognize the importance of educating
people about basic maternal and child health care. Developing countries that have
significantly lowered their TFRs credit many of these results to effective family planning
programs.
49
Prenatal care and proper birth spacing make women healthier. In turn, healthier women
give birth to healthier babies, leading to fewer infant deaths. Family planning services
provide information on reproductive physiology and contraceptives, as well as on the
actual contraceptive devices available, to people who wish to control the number of
children they have or to space out their children’s births. Family planning programs are
most effective when they are designed with sensitivity to local social and cultural beliefs.
Family planning services don’t try to force people to limit their family sizes; rather, they
attempt to convince people that small families (and the contraceptives that promote small
families) are acceptable and desirable. Contraceptive use is strongly linked to lower
TFRs. Research has shown that 90 percent of the decrease in fertility in 31 developing
countries was a direct result of increased knowledge and availability of contraceptives. In
highly developed countries, where TFRs are at replacement levels or lower, an average
of 72 percent of married women of reproductive age use contraceptives for birth control.
Activity:
1. How does the study of population ecology help us understand why some
populations grow, some remain stable, and others decline?
2. Why has human population growth, which increased exponentially for centuries,
started to decline in the past few decades?
3. What is carrying capacity? Do you think carrying capacity applies to people as well
as to other organisms? Why or why not?
Additional Resources:
Carson, R. L. (1964). Silent spring. Greenwich, Conn: Fawcett.
http://www.life.illinois.edu/bio100/lectures/s10lects/04s10-population9ind.html
https://www.khanacademy.org/science/biology/ecology/population-growth-andregulation/a/mechanisms-of-population-regulation
https://populationeducation.org/what-biotic-potential/
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Module 6:
Earth’s Natural Resources
Time Frame: 3 Weeks (Week 12-14)
Overview:
I.
Earth’s Natural Resources
A. Food and soil resources
1.
Green revolution agriculture
a. Soil erosion
b. Pesticide toxicity- biomagnification and bioaccumulation
c. Bioengineering: Genetically modified crops (GMOs)
2.
Sustainable agriculture
B. Water and air resources
C. Petroleum resources/fossil fuels
D. Nuclear power
E. Renewable and sustainable energy resources
Objectives:
1. Identify fossil fuels as the major sources of energy for industrialized nations.
2. Differentiate between nonrenewable and renewable sources of energy.
3. Differentiate between resources and reserves.
4. Describe three factors that cause the amount of reserves to change.
5. Identify the different threats to the Earth’s natural resources.
6. Explain and articulate the trends and status of the different resources of the planet.
7. Describe four environmental issues related to the use of biomass to provide energy.
8. Describe environmental issues related to the development of hydroelectric power.
9. Describe how active and passive solar heating designs differ.
10. Describe two methods used to generate electricity from solar energy.
11. Describe how wind, geothermal, and tidal energy are used to produce electricity.
12. Recognize that wind, geothermal, and tidal energy can be developed only in areas
with the proper geologic or geographical features.
13. Recognize that energy conservation can significantly reduce our need for additional
energy sources.
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I.
Earth’s Natural Resources
Lesson 1. Food and Soil Resources
This topic aims to develop the understanding of the attributes of soil required to support
good plant growth, how these attributes may deteriorate under various practices, and
what is necessary to maintain a productive soil specifically for agricultural purposes and
food production.
Soil can be defined as solid material of geological and biological origin that is changed
by chemical, biological, and physical processes, giving it the ability to support plant
growth. A rich soil is much more than the dirt you might get out of any hole in the ground.
Indeed, agriculturists cringe when anyone refers to soil as “dirt.” The quality of soil can
make the difference between harvesting an abundant crop and abandoning a field to
weeds.
1. The Green Revolution
Throughout history there have been many revolutions that have occurred and changed
human lives, such as Intellectual Revolution and the Industrial Revolution. In the mid- and
late-20th century a revolution occurred that dramatically changed the field of agriculture,
and this revolution was known as the Green Revolution.
The Green Revolution was a period when the productivity of global agriculture increased
drastically as a result of new advances. During this time period, new chemical fertilizers
and synthetic herbicides and pesticides were created. The chemical fertilizers made it
possible to supply crops with extra nutrients and, therefore, increase yield. The newly
developed synthetic herbicides and pesticides-controlled weeds, deterred or kill insects,
and prevented diseases, which also resulted in higher productivity.
In addition to the chemical advances utilized during this time period, high-yield crops were
also developed and introduced. High-yield crops are crops that are specifically designed
to produce more overall yield. A method known as multiple cropping was also
implemented during the Green Revolution and lead to higher productivity. Multiple
cropping is when a field is used to grow two or more crops throughout the year, so that
the field constantly has something growing on it. These new farming techniques and
advances in agricultural technology were utilized by farmers all over the world, and when
combined, intensified the results of the Green Revolution.
a. Benefits of the Green Revolution
As a result of the Green Revolution and the introduction of chemical fertilizers, synthetic
herbicides and pesticides, high-yield crops, and the method of multiple cropping, the
agricultural industry was able to produce much larger quantities of food. This increase in
productivity made it possible to feed the growing human population.
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One person who is famous for his involvement in the Green Revolution is the scientist
Norman Borlaug. In the 1940s, Norman Borlaug developed a strain of wheat that could
resist diseases, was short, which reduced damage by wind, and could produce large seed
heads and high yields. He introduced this variety of wheat in Mexico and within twenty
years the production of wheat had tripled. This allowed for the production of more food
for people in Mexico and also made it possible for Mexico to export their wheat and sell it
in other countries. Norman Borlaug helped introduce this high-yield variety of wheat to
other countries in need of increased food production, and he eventually won a Nobel
Peace Prize for his work with developing high-yield crops and for helping prevent
starvation in many developing countries.
In addition to producing larger quantities of food, the Green Revolution was also beneficial
because it made it possible to grow more crops on roughly the same amount of land with
a similar amount of effort. This reduced production costs and also resulted in cheaper
prices for food in the market.
The ability to grow more food on the same amount of land was also beneficial to the
environment because it meant that less forest or natural land needed to be converted to
farmland to produce more food. This is demonstrated by the fact that from 1961 to 2008,
as the human population increased by 100% and the production of food rose by 150%,
the amount of forests and natural land converted to farm only increased by 10%. The
natural land that is currently not needed for agricultural land is safe for the time being,
and can be utilized by animals and plants for their natural habitat.
b. Issues with the Green Revolution
Although the Green Revolution had several benefits, there were also some issues
associated with this period that affected both the environment and society. The use of
chemical fertilizers and synthetic herbicides and pesticides dramatically influenced the
environment by increasing pollution and erosion. The new materials added to the soil and
plants polluted the soil and water systems around the fields. The pollution of the water
exposed people and the environment downstream to the chemicals being used in the
farm fields. The pollution of the soil resulted in lower soil quality, which increased the risk
of erosion of the topsoil.
i. Soil Erosion and Soil Degradation
In natural ecosystems, there is always a turnover of plant material, so new detritus is
continuously being added to topsoil. However, when humans cut forests, graze livestock,
or grow crops (in an unsustainable manner), the soil is at the mercy of their management
or mismanagement. Soil degradation is a reduction in the capacity of soil to support plant
life and to perform ecosystem functions. One of the most critical forms of soil
degradation is erosion.
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Forms of Erosion
How is topsoil lost? The most pervasive and damaging force is erosion, which occurs
when water and wind pick up particles of soil and carry them away. Erosion occurs any
time soil is exposed to the elements. The removal may be slow and subtle, as when soil
is gradually blown away by wind, or it may be dramatic, as when gullies are washed out
in a storm.
In most natural terrestrial ecosystems, a vegetative cover protects against erosion. The
vegetation intercepts falling raindrops, and the water infiltrates gently into the loose topsoil
without disturbing its structure. With good infiltration, runoff is minimal. Runoff that does
occur is slowed as the water moves through the vegetative or litter mat. Similarly,
vegetation slows the velocity of wind and holds soil particles.
-
Splash, Sheet, and Gully Erosion.
When soil is left bare and unprotected, it is easily eroded. Splash erosion occurs in
storms as the impact of falling raindrops breaks up the clumpy structure of the topsoil.
The dislodged particles wash into spaces between other aggregates, clogging pores and
thereby decreasing infiltration and aeration. The decreased infiltration results in more
water running off, carrying away the fine particles from the surface, a phenomenon called
sheet erosion. As further runoff occurs, the water converges into rivulets and streams,
which have greater volume, velocity, and energy and hence greater capacity to pick up
and re- move soil. The result is erosion into gullies, or gully erosion. This process of
erosion can become a cycle that perpetuates itself.
-
Desert Pavement and Cryptogamic Crusts.
Both wind and water erosion involve the differential removal of soil particles. The lighter
particles of humus and clay are the first to be carried away, while rocks, stones, and
coarse sand remain behind. Consequently, as erosion removes the finer materials, the
remaining soil becomes progressively coarser—sandy, stony, and finally, rocky. Such
coarse soils frequently reflect past or ongoing erosion. Did you ever wonder why deserts
are full of sand? The sand is what remains after the finer, lighter clay and silt particles
have blown away. In some deserts, however, the removal of fine material by wind has left
a thin surface layer of stones and gravel called a desert pavement, which protects the
underlying soil against further erosion. Vehicular and pedestrian traffic damage this
surface layer, allowing another episode of erosion to commence.
Soil with a crust hardened from drying may be colonized by certain kinds of primitive
plants (algae, lichens, and mosses) called cryptogams. Their growth and colonization
create a crust on the soil, called a cryptogamic crust. Such crusts have a positive
ecological impact; they stabilize soil, slow erosion, and add nutrients through nitrogen
fixation. However, they can also inhibit water infiltration and seed generation.
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Cryptogramic crust is readily broken up by livestock trampling or human intrusion. If the
soil below is loosened, it can again be subject to wind and water erosion.
Practices that Cause erosion
Erosion is one of the main elements of soil degradation. Practices that expose soil to
erosion include overcultivation, overgrazing, and deforestation, all of which are a
consequence of unsustainable management practices. Yet as we will see, many of the
impacts of these practices can be reversed.
-
Overcultivation
Traditionally, the first step in growing crops has been plowing to control weeds. The
drawback is that the soil is then exposed to erosion by wind and water. Further, the soil
may remain bare for a considerable time after planting and again after harvest. Plowing
is frequently considered necessary to loosen soil to improve aeration and infiltration
through it, yet all too often the effect is just the reverse. Splash erosion destroys soil’s
aggregate structure and seals its surface, so that aeration and infiltration are decreased. The weight of the tractors used in plowing compacts the soil. Plowing also
accelerates the loss of water through evaporation.
Despite the harmful impacts inherent in cultivation, systems of crop rotation—a cash
crop such as corn every third year, with hay and clover (which fixes nitrogen as well as
adding organic matter) in between—have proved sustainable. If farmers abandon crop
rotation, degradation and erosion exceed regenerative processes, and the result is a
decline in the quality of soil. This is the essence of overcultivation.
-
Overgrazing
Grasslands that are too steep or receive too little rainfall to support cultivated crops
have traditionally been used for grazing livestock. In fact, about two-thirds of dryland
areas are rangelands. Unfortunately, such lands are often overgrazed. As grass
production fails to keep up with consumption, erosion follows and the land becomes
barren.
Overgrazing is not a new problem. In the United States in the 1800s, the American
bison were slaughtered to starve out Native Americans and allow for stocking the
rangelands with cattle. Cattle overgrazing became rampant, leading to erosion and
encroachment by hardy desert plants such as sagebrush, mesquite, and juniper, which
are not palatable to cattle. Western rangelands now produce less than half the livestock
forage they produced before the advent of commercial grazing. desertification affects
some 85% of North America’s dry-lands and that the most widespread cause of
rangeland are public lands that are not owned by the people who graze the animals.
55
Where this is the case, herders who choose to have fewer livestock on the range
sacrifice income, while others continue to overgraze the range.
-
Deforestation
Forest ecosystems are extremely efficient at holding and recycling nutrients and at
absorbing and holding water because they maintain and protect very porous, humus-rich
topsoil. Investigators at Hubbard Brook Forest in New Hampshire found that converting a
hillside from forest to grassland doubled the amount of runoff and increased the leaching
of nutrients many-fold. Much worse is what occurs if the forest is simply cut and its soil is
left exposed. The topsoil becomes saturated with water and the muddy mass slides off
the slope and into waterways, leaving only barren subsoil, which continues to erode.
Forests continue to be cleared at an alarming rate. The problem is particularly acute when
tropical rain forests are cut. Because of leaching by rainwater, tropical soils (oxisols) are
notoriously lacking in nutrients. When the forests are cleared, the thin layer of humus with
nutrients readily washes away. Only the nutrient-poor subsoil is left.
ii.
Pesticide Toxicity
In addition to chemical fertilizers, mechanized monoculture requires large amounts of
other agricultural chemicals, such as pesticides, growth regulators, and preservatives. It
is important to have an understanding of basic terms used to discuss the various
chemicals employed to control pests. A pesticide is any chemical used to kill or control
populations of unwanted fungi, animals, or plants, often called pests. The term pest is not
scientific but refers to any organism that is unwanted. Insects that feed on crops are pests,
while others, such as bees, are beneficial for pollinating plants. Unwanted plants are
generally referred to as weeds.
Pesticides can be subdivided into several categories based on the kinds of organisms
they are used to control. Insecticides are used to control insect populations by killing them.
Unwanted fungal pests that can weaken plants or destroy fruits are controlled by
fungicides. Mice and rats are killed by rodenticides, and plant pests (weeds) are controlled
by herbicides. Since pesticides do not kill just pests but can kill a large variety of living
things, including humans, these chemicals might be more appropriately called biocides.
A perfect pesticide is one that kills or inhibits the growth of only the specific pest organism
causing a problem. The pest is often referred to as the target organism. However, most
pesticides are not very specific and kill many nontarget organisms as well. For example,
most insecticides kill both beneficial and pest species, rodenticides kill other animals as
well as rodents, and most herbicides kill a variety of plants, both pests and non-pests.
Many of the older pesticides were very stable and remained active for long periods of
time. These are called persistent pesticides. Pesticides that break down quickly are called
nonpersistent pesticides.
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-
Insecticides
If insects are not controlled, they consume a large proportion of the crops produced by
farmers. In small garden plots, insects can be controlled by manually removing them and
killing them. However, in large fields, this is not practical, so people have sought other
ways to control pest insects.
The first synthetic organic insecticide to be used was DDT [1,1,1-trichloro-2,2-bis(pchlorophenyl)ethane]. DDT was originally thought to be the perfect insecticide. It was
inexpensive, long-lasting, relatively harmless to humans, and very deadly to insects. After
its discovery, it was widely used in agriculture and to control disease-carrying insects.
During the first ten years of its use (1942– 52), DDT is estimated to have saved five million
lives, primarily because of its use in controlling disease-carrying mosquitoes.
However, scientists began to recognize several problems associated with the use of DDT.
They documented that insect populations that were repeatedly subjected to spraying by
DDT developed resistance to it and larger doses were required to kill the pest insects.
Ecologists and crop scientists did studies on how the death of non-target organisms
affected surrounding ecosystems and natural predators and parasites of pest insects.
This was a particular problem because DDT is a persistent chemical. Studies of the
breakdown of DDT in the environment showed that it had a long half-life.
Finally, it was discovered that because it is persistent, DDT tends to accumulate and
reach higher concentrations in older animals and in animals at higher trophic levels. The
problem was particularly acute in species of birds such as eagles, pelicans, and
cormorants that were predators on fish. Scientists documented that as DDT levels in the
birds increased, they produced eggs with thin shells, which were easily broken in the nest.
Consequently, the populations of these birds dropped precipitously.
Chlorinated hydrocarbons are a group of pesticides of complex, stable structure
that contain carbon, hydrogen, and chlorine. DDT was the first such pesticide
manufactured, but several others have been developed. Other chlorinated
hydrocarbons are chlordane, aldrin, heptachlor, dieldrin, and endrin. It is not fully
understood how these compounds work, but they are believed to affect the nervous
systems of insects, resulting in their death.
Organophosphates and Carbamates. Because of the problems associated with
persistent insecticides, nonpersistent insecticides that decompose to harmless
products in a few hours or days were developed. However, like other insecticides,
these are not species-specific; they kill beneficial insects as well as harmful ones.
Although the short half-life prevents the accumulation of toxic material in the
environment, it is a disadvantage for farmers, since more frequent applications are
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required to control pests. This requires more labor and fuel and, therefore, is more
expensive.
-
Herbicides
Weeds are plants we do not want to have growing in a particular place. Weed control is
extremely important for agriculture because weeds take nutrients and water from the soil,
making them unavailable to the crop species. In addition, weeds may shade the crop
species and prevent it from getting the sunlight it needs for rapid growth. At harvest time,
weeds reduce the efficiency of harvesting machines. Also, weeds generally must be
sorted from the crop before it can be sold, which adds to the time and expense of
harvesting.
Many of the recently developed herbicides can be very selective if used appropriately.
Some are used to kill weed seeds in the soil before the crop is planted, while others are
used after the weeds and the crop begin to grow. In some cases, a mixture of herbicides
can be used to control several weed species simultaneously.
-
Fungicides and Rodenticides
Fungus pests can be divided into two categories. Some are natural decomposers of
organic material, but when the organic material being destroyed happens to be a crop or
other product useful to humans, the fungus is considered a pest. Other fungi are parasites
on crop plants; they weaken or kill the plants, thereby reducing the yield. Fungicides are
used as fumigants (gases) to protect agricultural products from spoilage, as sprays and
dusts to prevent the spread of diseases among plants, and as seed treatments to protect
seeds from rotting in the soil before they have a chance to germinate. Methylmercury is
often used on seeds to protect them from spoilage before germination. However, since
methylmercury is extremely toxic to humans, these seeds should never be used for food.
To reduce the chance of a mix- up, treated seeds are usually dyed a bright color.
iii.
Bio-engineering: Genetically Modified Crops
Farmers have been involved in manipulating the genetic makeup of their plants and
animals since these organisms were first domesticated. Initially, farmers either
consciously or accidentally chose to plant specific seeds or breed certain animals that
had specific desirable characteristics. In the past, if pests devastated a field of crops and
a few plants stayed alive and healthy, the seeds from these healthy plants were used to
generate the next crop. Thus, the beneficial factors that made the plants resistant were
transferred to the next generation, making the new generation of crops slightly more
resistant to the same pests. This resulted in local varieties with particular characteristics.
When the laws of genetics began to be understood in the early 1900s, scientists began
to make precise crosses between carefully selected individuals to enhance the likelihood
that their offspring would have certain highly desirable characteristics. This led to the
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development of hybrid seeds and specific breeds of domesticated animals. Controlled
plant and animal breeding resulted in increased yields and better disease resistance in
domesticated plants and animals. These activities are still the major driving force for
developing improved varieties of domesticated organisms.
-
Genetically Modified Crops
When the structure of DNA was discovered and it was determined that the DNA of
organisms could be manipulated, an entirely new field of plant and animal breeding arose.
Genetic engineering or biotechnology involves inserting specific pieces of DNA into the
genetic makeup of organisms. The organism with the altered genetic makeup is known
as a genetically modified organism. The DNA inserted could be from any source, even an
entirely different organism.
In agricultural practice, two kinds of genetically modified organisms have received
particular attention. One involves the insertion of genes from a specific kind of bacterium
called Bacillus thuringiensis israeliensis (Bti). The bacterial genes produce a material that
causes the destruction of the lining of the gut of insects that eat it. It is a natural insecticide
that is a part of the plant. To date, these genes have been inserted into the genetic
makeup of several crop plants, including corn and cotton.
A second kind of genetic engineering involves inserting a gene for herbicide resistance
into the genome of certain crop plants. The value of this to farmers is significant. For
example, a farmer can plant cotton with very little preparation of the field to rid it of weeds.
When both the cotton and the weeds begin to grow, the field is sprayed with a specific
herbicide that will kill the weeds but not harm the cotton because it contains genes that
allow it to resist the effects of the herbicide.
The use of genetically modified crops has become extremely important worldwide. Three
crops are particularly important: corn (maize), soybeans, and cotton. In the United States,
at least 90 percent of cotton, soybeans, and corn grown are genetically modified.
Worldwide 81 percent of soybeans and cotton, 35 percent of corn, and 30 percent of
rapeseed (canola) are genetically modified. The United States accounts for 40 percent of
all genetically modified crops planted globally.
Many groups oppose the use of genetically modified organisms. They argue that this
technology is going a step too far, that no long-term studies have been done to ensure
their safety, that there are dangers we cannot anticipate, and that if such crops are grown,
they should be labeled so that the public knows when they are consuming products from
genetically modified organisms.
Supporters argue that all plant and animal breeding involve genetic manipulation and that
this is just a new kind of genetic manipulation. A great deal of evidence exists that genes
travel between species in nature and that genetic engineering simply makes a common,
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natural process more frequent. Over the next 20 to 30 years, scientists hope to use
biotechnology to produce high-yield plant strains that are more resistant to insects and
disease, thrive on less fertilizer, make their own nitrogen fertilizer, do well in slightly salty
soils, withstand drought, and use solar energy more efficiently during photosynthesis.
These new kinds of genetically modified organisms will continue to be developed and
tested, and the political arguments about their appropriateness will continue as well.
A. Sustainable Agriculture
What Is Sustainable Agriculture?
If you had to choose, which would you prefer to eat: food that is grown more naturally or
food that is enhanced by spraying it with pesticides or applying chemical fertilizers?
Most people would prefer the natural food that is free of chemicals and artificial
enhancements. Unfortunately, the majority of food we consume is produced
using industrialized agriculture, which is a type of agriculture where large quantities of
crops and livestock are produced through industrial techniques for the purpose of sale.
This type of agriculture relies heavily on a variety of chemicals and artificial enhancements,
such as pesticides, fertilizers, and genetically modified organisms. This type of agriculture
also uses a large amount of fossil fuels and large machines to manage the farm land.
Although industrialized agriculture has made it possible to produce large quantities of food,
due to the negative aspects of this technique, there has been a shift towards sustainable
agriculture.
Sustainable agriculture is a type of agriculture that focuses on producing long-term
crops and livestock while having minimal effects on the environment. This type of
agriculture tries to find a good balance between the need for food production and the
preservation of the ecological system within the environment. In addition to producing
food, there are several overall goals associated with sustainable agriculture, including
conserving water, reducing the use of fertilizers and pesticides, and promoting biodiversity
in crops grown and the ecosystem. Sustainable agriculture also focuses on maintaining
economic stability of farms and helping farmers improve their techniques and quality of
life.
There are many farming strategies that are used that help make agriculture more
sustainable. Some of the most common techniques include growing plants that can create
their own nutrients to reduce the use of fertilizers and rotating crops in fields, which
minimizes pesticide use because the crops are changing frequently. Another common
technique is mixing crops, which reduces the risk of a disease destroying a whole crop
and decreases the need for pesticides and herbicides. Sustainable farmers also utilize
water management systems, such as drip irrigation, that waste less water.
a. Benefits of Sustainable Agriculture
There are many benefits of sustainable agriculture, and overall, they can be divided into
human health benefits and environmental benefits.
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-
On human health:
•
-
Crops grown through sustainable agriculture are better for people. Due to the
lack of chemical pesticides and fertilizers, people are not being exposed to or
consuming synthetic materials. This limits the risk of people becoming ill from
exposure to these chemicals. In addition, the crops produced through
sustainable agriculture can also be more nutritious because the overall crops
are healthier and more natural.
On the environment:
•
One major benefit to the environment is that sustainable agriculture uses 30%
less energy per unit of crop yield in comparison to industrialized agriculture.
This reduced reliance on fossil fuels results in the release of less chemicals
and pollution into the environment.
•
Maintaining soil quality, reducing soil degradation and erosion, and saving
water. I
•
Increases biodiversity of the area by providing a variety of organisms with
healthy and natural environments to live in.
•
More sustainable agriculture can help reduce excessive dependence on oil
by increasing the use of renewable fuels. Some farmers have shown that they
can use energy from the sun, wind, and flowing water, and natural gas
produced from farm wastes for most or all of the energy they need for food
production.
b. Shifting to Sustainable Agriculture
Analysts suggest four major strategies to help farmers make the transition to more
sustainable organic agriculture:
1. greatly increase research on sustainable agriculture and human nutrition;
2. set up demonstration projects so farmers can see how more sustainable organic
agricultural systems work;
3. provide subsidies and increased foreign aid to encourage its use;
4. establish training programs in sustainable organic agriculture for farmers and
government agricultural officials, and encourage the creation of college curricula
in sustainable organic agriculture and human nutrition.
Activity:
1. List three changes in your lifestyle that could reduce your impact on soil erosion.
Which, if any, of these changes are you willing to make?
2. What are the three most important actions you would take to reduce hunger (a)
in the country where you live and (b) in the world?
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Lesson 2: Water and Air resources
Earth’s Water Resources
Earth’s oceans contain 97% of the planet’s water, so just 3% is fresh water, water with
low concentrations of salts. Most fresh water is trapped as ice in the vast glaciers and ice
sheets of Greenland. A storage location for water such as an ocean, glacier, pond, or
even the atmosphere is known as a reservoir. A water molecule may pass through a
reservoir very quickly or may remain for much longer. The amount of time a molecule
stays in a reservoir is known as its residence time. Earth’s oceans contain 97% of the
planet’s water, so just 3% is fresh water, water with low concentrations of salts. Most fresh
water is trapped as ice in the vast glaciers and ice sheets of Greenland. A storage location
for water such as an ocean, glacier, pond, or even the atmosphere is known as a reservoir.
A water molecule may pass through a reservoir very quickly or may remain for much
longer. The amount of time a molecule stays in a reservoir is known as its residence time.
Three States of Water
Because of the unique properties of water, water molecules can cycle through almost
anywhere on Earth. The water molecule found in your glass of water today could have
erupted from a volcano early in Earth history. In the intervening billions of years, the
molecule probably spent time in a glacier or far below the ground. The molecule surely
was high up in the atmosphere and maybe deep in the belly of a dinosaur. Where will that
water molecule go next? Water is the only substance on Earth that is present in all three
states of matter – as a solid, liquid or gas. Along with that, Earth is the only planet where
water is present in all three states. Because of the ranges in temperature in specific
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locations around the planet, all three phases may be present in a single location or in a
region. The three phases are solid (ice or snow), liquid (water), and gas (water vapor).
The Water Cycle
Because Earth’s water is present in all three states, it can get into a variety of
environments around the planet. The movement of water around Earth’s surface is
the hydrologic (water) cycle. The Sun, many millions of kilometers away, provides the
energy that drives the water cycle. Our nearest star directly impacts the water cycle by
supplying the energy needed for evaporation. Most of Earth’s water is stored in the
oceans where it can remain for hundreds or thousands of years. The oceans are
discussed in detail in the chapter Earth’s Oceans.
Water changes from a liquid to a gas by evaporation to become water vapor. The Sun’s
energy can evaporate water from the ocean surface or from lakes, streams, or puddles
on land. Precipitation can be rain, sleet, hail, or snow. Sometimes precipitation falls back
into the ocean and sometimes it falls onto the land surface.
When water falls from the sky as rain it may enter streams and rivers that flow downward
to oceans and lakes. Water that falls as snow may sit on a mountain for several months..
Snow and ice slowly melt over time to become liquid water, which provides a steady flow
of fresh water to streams, rivers, and lakes below. A water droplet falling as rain could
also become part of a stream or a lake. At the surface, the water may eventually evaporate
and reenter the atmosphere.
A significant amount of water infiltrates into the ground. Soil moisture is an important
reservoir for water. Water trapped in soil is important for plants to grow. Water may seep
through dirt and rock below the soil through pores infiltrating the ground to go into Earth’s
groundwater system. Groundwater enters aquifers that may store fresh water for
centuries. Alternatively, the water may come to the surface through springs or find its way
back to the oceans. Plants and animals depend on water to live and they also play a role
in the water cycle. Plants take up water from the soil and release large amounts of water
vapor into the air through their leaves, a process known as transpiration. People also
depend on water as a natural resource.
Water forms/Sources of Water
a. Streams and Rivers
Fresh water in streams, ponds, and lakes is an extremely important part of the water cycle
if only because of its importance to living creatures. Along with wetlands, these fresh
water regions contain a tremendous variety of organisms. Streams are bodies of water
that have a current; they are in constant motion. Geologists recognize many categories
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of streams depending on their size, depth, speed, and location. Creeks, brooks, tributaries,
bayous, and rivers might all be lumped together as streams. In streams, water always
flows downhill, but the form that downhill movement takes varies with rock type,
topography, and many other factors. Stream erosion and deposition are extremely
important creators and destroyers of landforms
b. Ponds and Lakes
Ponds and lakes are bordered by hills or low rises, so that the water is blocked from
flowing directly downhill. Ponds are small bodies of fresh water that usually have no outlet;
ponds are often are fed by underground springs. Lakes are larger bodies of water. Lakes
are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water
usually drains out of a lake through a river or a stream and all lakes lose water to
evaporation.
c. Wetlands
They are lands that are wet for significant periods of time. They are common where water
and land meet. Wetlands can be large flat areas or relatively small and steep areas.
Wetlands are rich and unique ecosystems with many species that rely on both the land
and the water for survival. Only specialized plants are able to grow in these conditions.
Wetlands tend have a great deal of biological diversity. Wetland ecosystems can also be
fragile systems that are sensitive to the amounts and quality of water present within them.
d. Groundwater
Although this may seem surprising, water beneath the ground is commonplace. Usually
groundwater travels slowly and silently beneath the surface, but in some locations, it
bubbles to the surface at springs. Groundwater is the largest reservoir of liquid fresh water
on Earth and is found in aquifers, porous rock and sediment with water in between. Water
is attracted to the soil particles and capillary action, which describes how water moves
through a porous media, moves water from wet soil to dry areas.
e. The Water Table
For a groundwater aquifer to contain the same amount of water, the amount of recharge
must equal the amount of discharge. What are the likely sources of recharge? What are
the likely sources of discharge? In wet regions, streams are fed by groundwater; the
surface of the stream is the top of the water table. In dry regions, water seeps down from
the stream into the aquifer. These streams are often dry much of the year. Water leaves
a groundwater reservoir in streams or springs. People take water from aquifers, too. What
happens to the water table when there is a lot of rainfall? What happens when there is a
drought? Although groundwater levels do not rise and fall as rapidly as at the surface,
over time the water table will rise during wet periods and fall during droughts.
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f.
Groundwater Use
Groundwater is an extremely important water source for people. Groundwater is a
renewable resource and its use is sustainable when the water pumped from the aquifer
is replenished. It is important for anyone who intends to dig a well to know how deep
beneath the surface the water table is.
g. Springs
Groundwater meets the surface in a stream, as shown below, or a spring. A spring may
be constant, or may only flow at certain times of year. Towns in many locations depend
on water from springs. Springs can be an extremely important source of water in locations
where surface water is scarce.
h. Wells
A well is created by digging or drilling to reach groundwater. When the water table is
close to the surface, wells are a convenient method for extracting water. When the water
table is far below the surface, specialized equipment must be used to dig a well. Most
wells use motorized pumps to bring water to the surface, but some still require people to
use a bucket to draw water up.
Air Resources
Air is not a unique element or compound. Rather, air is a mixture of many discrete gases,
each with its own physical properties, in which varying quantities of tiny solid and liquid
particles are suspended.
Major Components
The composition of air is not constant; it varies from time to time and from place to place.
If the water vapor, dust, and other variable components were removed from the
atmosphere, we would find that its makeup is very stable worldwide up to an altitude of
about 80 kilometers (50 miles).
Two gases—nitrogen and oxygen—make up 99 percent of the volume of clean, dry air.
Although these gases are the most plentiful components of air and are of great
significance to life on Earth, they are of minor importance in affecting weather
phenomena. The remaining 1percent of dry air is mostly the inert gas argon (0.93 percent)
plus tiny quantities of a number of other gases. Carbon dioxide, although present in only
minute amounts (0.037 percent), is nevertheless an important constituent of air. Carbon
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dioxide is of great interest to meteorologists because it is an efficient absorber of energy
emitted by Earth and thus influences the heating of the atmosphere.
Variable Components
Air includes many gases and particles that vary significantly from time to time and place
to place. Important examples include water vapor, dust particles, and ozone. Although
usually present in small percentages, they can have significant effects on weather and
climate.
The amount of water vapor in the air varies considerably, from practically none at all up
to about 4 percent by volume. Why is such a small fraction of the atmosphere so
significant? Certainly, the fact that water vapor is the source of all clouds and precipitation
would be enough to explain its importance. However, water vapor has other roles. Like
carbon dioxide, it has the ability to absorb heat given off by Earth as well as some solar
energy. It is therefore important when we examine the heating of the atmosphere.
When water changes from one state to another, it absorbs or releases heat. This energy
is termed latent heat, which means “hidden heat.” As we shall see in later chapters, water
vapor in the atmosphere transports this latent heat from one region to another, and it is
the energy source that helps drive many storms.
The movements of the atmosphere are sufficient to keep a large quantity of solid and
liquid particles suspended within it. Although visible dust sometimes clouds the sky, these
relatively large particles are too heavy to stay in the air for very long. Still, many particles
are microscopic and remain suspended for considerable periods of time. They may
originate from many sources, both natural and human made, and include sea salts from
breaking waves, fine soil blown into the air, smoke and soot from fires, pollen and
microorganisms lifted by the wind, ash and dust from volcanic eruptions, and more.
Collectively, these tiny solid and liquid particles are called aerosols.
From a meteorological standpoint, these tiny, often invisible particles can be significant.
First, many acts as surfaces on which water vapor can condense, an important function
in the formation of clouds and fog. Second, aerosols can absorb, reflect, and scatter
incoming solar radiation. Thus, when an air-pollution episode is occurring or when ash
fills the sky following a volcanic eruption, the amount of sunlight reaching Earth’s surface
can be measurably reduced. Finally, aerosols contribute to an optical phenomenon we
have all observed—the varied hues of red and orange at sunrise and sunset
Ozone
Another important component of the atmosphere is ozone. It is a form of oxygen that
combines three oxygen atoms into each molecule (O3). Ozone is not the same as oxygen
we breathe, which has two atoms per molecule (O 2). There is very little of this gas in the
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atmosphere, and its distribution is not uniform. In the lowest portion of the atmosphere,
ozone represents less than one part in 100 million. It is concentrated well above the
surface in a layer called the stratosphere, between 10 and 50 kilometers.
In this altitude range, oxygen molecules (O 2) are split into single atoms of oxygen (O)
when they absorb ultraviolet radiation emitted by the Sun. Ozone is then created when a
single atom of oxygen (O) and a molecule of oxygen (O 2) collide. This must hap- pen in
the presence of a third, neutral molecule that acts as a catalyst by allowing the reaction
to take place without itself being consumed in the process. Ozone is concentrated in the
10- to 50- kilometer height range because a crucial balance exists there: The ultraviolet
radiation from the Sun is sufficient to produce single atoms of oxygen, and there are
enough gas molecules to bring about the required collisions.
The presence of the ozone layer in our atmosphere is crucial to those of us who dwell on
Earth. The reason is that ozone absorbs the potentially harmful ultraviolet (UV) radiation
from the Sun. If ozone did not filter a great deal of the ultraviolet radiation, and if the Sun’s
UV rays reached the surface of Earth undiminished, our planet would be uninhabitable
for most life as we know it. Thus, anything that reduces the amount of ozone in the
atmosphere could affect the well-being of life on Earth.
Troposphere
The bottom layer in which we live, where temperature decreases with an increase in
altitude, is the troposphere. The term literally means the region where air “turns over” a
reference to the appreciable vertical mixing of air in this lowermost zone. The troposphere
is the chief focus of meteorologists, because it is in this layer that essentially all important
weather phenomena occur.
The temperature decrease in the troposphere is called the environmental lapse rate. Its
average value is 6.5° C per kilometer (3.5° F per 1,000 feet), a figure known as the normal
lapse rate. It should be emphasized, however, that the environmental lapse rate is not
constant, but rather can be highly variable, and must be regularly measured.
Stratosphere
Beyond the tropopause is the stratosphere. In the stratosphere, the temperature remains
constant to a height of about 20 kilometers (12 miles) and then begins a gradual increase
that continues until the stratopause, at a height of nearly 50 kilometers (30 miles) above
Earth’s surface. Below the tropopause, atmospheric properties like temperature and
humidity are readily transferred by large-scale turbulence and mixing. Above the
tropopause, in the stratosphere, they are not. Temperatures increase in the stratosphere
because it is in this layer that the atmosphere’s ozone is concentrated. Recall that ozone
absorbs ultraviolet radiation from the Sun. As a consequence, the stratosphere is heated.
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Mesosphere
In the third layer, the mesosphere, temperatures again decrease with height until, at the
mesopause, more than 80 kilometers (50 miles) above the surface, the temperature
approaches —90°C(—130°F). The coldest temperatures any- wherein the atmosphere
occur at the mesopause. Because accessibility is difficult, the mesosphere is one of the
least explored regions of the atmosphere. The reason is that it cannot be reached by the
highest research balloons nor is it accessible to the lowest orbiting satellites. Recent
technological developments are just beginning to fill this knowledge gap.
Thermosphere
The fourth layer extends outward from the mesopause and has no well-defined upper
limit. It is the thermosphere, a layer that contains only a tiny fraction of the atmosphere’s
mass. In the extremely rarefied air of this outermost layer, temperatures again increase,
owing to the absorption of very short-wave, high-energy solar radiation by atoms of
oxygen and nitrogen.
Temperatures rise to extremely high values of more than lOO0° C in the thermosphere.
But such temperatures are not com- parable to those experienced near Earth’s surface.
Temperature is defined in terms of the average speed at which molecules move. Because
the gases of the thermosphere are moving at very high speeds, the temperature is very
high. But the gases are so sparse that, collectively, they possess only an insignificant
quantity of heat. For this reason, the temperature of a satellite orbiting Earth in the
thermosphere is determined chiefly by the amount of solar radiation it absorbs and not by
the high temperature of the almost nonexistent surrounding air. If an astronaut inside were
to expose his or her hand, it would not feel hot.
Lesson 3: Petroleum Resources/Fossil Fuels
Fossil fuels are the remains of once-living organisms that were pre- served and altered
as a result of geologic forces. Significant differences exist in the formation of coal from
that of oil and natural gas. Biological and geologic processes in various parts of the
geologic cycle produce the sedimentary rocks in which we find coal—are our primary
energy sources; they provide approximately 90% of the energy consumed worldwide.
Coal
Coal was formed from plant material that had been subjected to heat and pressure.
Freshwater swamps covered many regions of the Earth 300 million years ago. Conditions
in these swamps favored extremely rapid plant growth, resulting in large accumulations
of plant material. Because this plant material collected under water, decay was inhibited,
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and a spongy mass of organic material formed. It is thought that the chemical nature of
these ancient plants and the lack of many kinds of decay organisms at that time also
contributed to the accumulation of plant material. Today we see deposits of plant
materials, known as peat, being formed in bogs.
Due to geologic changes in the Earth, some of these organic deposits were submerged
by seas. The plant material that had collected in the swamps was then covered by
sediment. The weight of the sediment on top of the deposit compressed it and heat from
the Earth caused the evaporation of water and other volatile compounds. Thus, the
original plant material was transformed into coal. Depending on the amount of time the
organic matter has been subjected to geologic processes, several different grades of coal
are produced.
Oil and Natural Gas
Oil and natural gas, like coal, are products from the past. They probably originated from
microscopic marine organisms. When these organisms died and accumulated on the
ocean bottom and were buried by sediments, their breakdown released oil droplets.
Gradually, the muddy sediment formed rock called shale, which contained dispersed oil
droplets. Although shale is common and contains a great deal of oil, extraction from shale
is difficult because the oil is not concentrated. However, in instances where a layer of
porous sand- stone formed on top of the oil-containing shale and an impermeable layer
of rock formed on top of the sandstone, concentrations of oil often form. Usually, the
trapped oil does not exist as a liquid mass but rather as a concentration of oil within
sandstone pores, where it accumulates because water and gas pressure force it out of
the shale. These accumulations of oil are more likely to occur if the rock layers were folded
by geological forces.
Natural gas, like oil, forms from fossil remains. If the heat generated within the Earth
reached high enough temperatures, natural gas could have formed along with or instead
of oil. This would have happened as the organic material changed to lighter, more volatile
(easily evaporated) hydrocarbons than those found in oil. The most common hydrocarbon
in natural gas is the gas methane (CH4). Water, liquid hydrocarbons, and other gases
may be present in natural gas as it is pumped from a well.
The conditions that led to the formation of oil and gas deposits were not evenly distributed
throughout the world. Figure 9.6 illustrates the geographic distribution of oil reserves. The
Middle East has about 50 percent of the world’s oil reserves. Figure 9.7 shows the
geographic distribution of natural gas reserves. Eurasia (primarily Russia) and the Middle
East have about 70 percent of the world’s natural gas reserves.
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Use of Fossil Fuels
The three nonrenewable fossil-fuel resources—coal, oil, and natural gas—supply over 80
percent of the energy consumed world- wide. Each fuel has advantages and
disadvantages and requires special techniques for its production and use.
Coal Use
Coal is the world’s most abundant fossil fuel, but it supplies less than 30 percent of the
energy used in the world. It varies in quality and is generally classified in four categories:
lignite, sub- bituminous, bituminous, and anthracite. Lignite (brown) coal has a high
moisture content and is crumbly in nature, which makes it the least desirable form. It has
a low energy content that makes transportation over long distances uneconomic.
Therefore, most lignite is burned in power plants built near the coal mine. Over 60 percent
of the lignite used is from Europe.
Sub-bituminous coal has a lower moisture content and a higher carbon content (46– 60
percent) than lignite and is typically used as fuel for electric power plants. Bituminous
(soft) coal has a low moisture content and a high car- bon content (60–86 percent). It is
primarily used in electrical power generation but is also used in other industrial
applications such as cement production and steel making. Bituminous coal is the most
widely used because it is the easiest to mine and the most abundant. It supplies about 20
percent of the world’s energy requirements. Anthracite (hard) coal is 86–98 percent
carbon. It is relatively rare and is used primarily in heating of buildings and for specialty
uses.
Oil Use
Worldwide about 33 percent of the energy consumed comes from oil. Oil has several
characteristics that make it superior to coal as a source of energy. Its extraction causes
less environmental damage than does coal mining. It is a more concentrated source of
energy than coal, it burns with less pollution, and it can be moved easily through pipes.
Almost half of the oil used in the United States is as gasoline for cars.
Natural Gas Use
Natural gas, the third major source of fossil-fuel energy, supplies over 20 percent of the
world’s energy. Although natural gas is used primarily for heat energy, it does have other
uses, such as the manufacture of petrochemicals and fertilizer. Methane contains
hydrogen atoms that are combined with nitrogen from the air to form ammonia, which can
be used as fertilizer.
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Lesson 4: Nuclear power
Hard as it may be to believe, nuclear energy is the energy contained in an atom’s nucleus.
Two nuclear processes can be used to release that energy to do work: fission and fusion.
Nuclear fission is the splitting of atomic nuclei, and nuclear fusion is the fusing, or
combining, of atomic nuclei. A by-product of both fission and fusion is the release of
enormous amounts of energy.
Nuclear energy for commercial use is produced by splitting atoms in nuclear reactors,
which are devices that produce controlled nuclear fission. In the United States, almost all
of these reactors use a form of uranium oxide as fuel.
Nuclear fusion, despite decades of research to try to develop it, remains only a theoretical
possibility.
All atoms are composed of a central region called the nucleus, which contains positively
charged protons and neutrons that have no charge. In most atoms, the various forces in
the nucleus are balanced and the nucleus is stable. However, some isotopes of atoms
are radioactive; that is, the nuclei of these atoms are unstable and spontaneously
decompose. Neutrons, electrons, protons, and other larger particles are released during
nuclear disintegration, along with a great deal of energy. The rate of decomposition is
consistent for any given isotope. It is measured and expressed as radioactive half-life,
which is the time it takes for one-half of the radioactive material to spontaneously
decompose.
Nuclear disintegration releases energy from the nucleus as radiation, of which there are
three major types:
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Alpha radiation consists of a moving particle composed of two neutrons and two
protons. Alpha radiation usually travels through air for less than a meter and can
be stopped by a sheet of paper or the outer, nonliving layer of the skin.
Beta radiation consists of moving electrons released from nuclei. Beta particles
travel more rapidly than alpha particles and will travel through air for a couple of
meters. They are stopped by a layer of clothing, glass, or aluminum.
Gamma radiation is a type of electromagnetic radiation that does not consist of
particles. Other forms of electromagnetic radiation are X rays, light, and radio
waves. Gamma radiation can pass through your body, several centimeters of lead,
or nearly a meter of concrete.
When a radioactive isotope disintegrates and releases particles, it becomes a different
kind of atom. For example, uranium-238 ultimately produces lead—but it goes through
several steps in the process.
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Nuclear Chain Reaction
In addition to releasing alpha, beta, and gamma radiation when they disintegrate, the
nuclei of a few kinds of atoms release neutrons. When moving neutrons hit the nuclei of
certain other atoms, they can cause those nuclei to split as well. An atom that has a
nucleus that will split is said to be fissionable and the process of splitting is known as
nuclear fission. If these splitting nuclei also release neutrons, they can strike the nuclei
of other atoms, which also disintegrate, resulting in a continuous process called a nuclear
chain reaction. (Only certain kinds of atoms are suitable for the development of a nuclear
chain reaction. The two materials commonly used in nuclear reactions are uranium-235
and plutonium-239. In addition, there must be a certain quantity of nuclear fuel (a critical
mass) in order for a nuclear chain reaction to occur. It is this process that results in the
large amounts of energy released from bombs or nuclear reactors.
Nuclear Fission Reactors
A nuclear reactor is a device that permits a sustained, controlled nuclear fission chain
reaction. There are four important materials that are involved in producing a controlled
nuclear chain reaction: the fuel, a moderator, control rods, and the core coolant.
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The fuel most commonly used in nuclear reactors is uranium-235 (U-235). When
the nucleus is split, two to three rapidly moving neutrons are released, along with
large amounts of energy that can be harnessed to do work.
Moderators are used to slow down the fast-moving neutrons so that they are more
effective in splitting other U-235 nuclei and maintaining a chain reaction. The most
commonly used moderators are water and graphite.
Control rods contain non-fissionable materials that absorb the neutrons produced
by fissioning uranium and prevent the neutrons from splitting other atoms. By
moving the control rods into the reactor the number of neutrons available to cause
fission is reduced and the reaction slows. If the control rods are withdrawn, more
fission occurs, and more particles, radiation, and heat are produced.
The coolant is needed to manage the large amount of heat produced within the
nuclear reactor. The coolant is needed to transfer the heat away from the reactor
core to the turbine to produce electricity. In most reactors the core coolant is water,
which also serves as the moderator, but gases and liquid metals can also be used
as coolants in special kinds of nuclear reactors.
In the production of electricity, a nuclear reactor serves the same function as burning a
fossil fuel. It produces heat, which converts water to steam to operate a turbine that
generates electricity. After passing through the turbine, the steam must be cooled, and
the water is returned to the reactor to be heated again. Various types of reactors have
been constructed to furnish heat for the pro- duction of steam. They differ in the moderator
used, in how the reactor core is cooled, and in how the heat from the core is used to
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generate steam. The three most common kinds of nuclear reactors are boiling-water
reactors, pressurized-water reactors, and heavy- water reactors.
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Boiling-water reactors use water as both a moderator and a reactor-core
coolant. Steam is formed within the reactor and transferred directly to the turbine,
which turns to generate electricity. A disadvantage of the boiling-water reactor is
that the steam passing to the turbine must be treated to remove any radiation.
Even then, some radioactive material is left in the steam; therefore, the generating
building must be shielded. About 20 percent of the nuclear reactors in the world
are boiling-water reactors.
Pressurized-water reactors also use water as a moderator and reactor-core
coolant but the water is kept under high pressure so that steam is not allowed to
form in the reactor. A secondary loop transfers the heat from the pressurized water
in the reactor to a steam generator. The steam is used to turn the turbine and
generate electricity. Such an arrangement reduces the risk of radiation in the
steam but adds to the cost of construction by requiring a secondary loop for the
steam generator. About 60 percent of the nuclear reactors in the world are
pressurized-water reactors. Most of the reactors currently under construction are
of this type.
Heavy-water reactors are a third type of reactor that uses water as a coolant.
This type of reactor was developed by Canadians and uses water that contains
the hydrogen isotope deuterium in its molecular structure as the reactor-core
coolant and moderator. Since the deuterium atom is twice as heavy as the more
common hydrogen isotope, the water that contains deuterium weighs slightly more
than ordinary water. Heavy-water reactors are similar to pressurized-water
reactors in that they use a steam generator to convert regular water to steam in a
secondary loop. The major advantage of a heavy-water reactor is that naturally
occurring uranium isotopic mixtures serve as a suitable fuel while other reactors
require that the amount of U-235 be enriched to obtain a suitable fuel. This is
possible because heavy water is a better neutron moderator than is regular water.
Since it does not require enriched fuel, the cost of producing fuel for a heavy-water
reactor is less than that for other reactors. About 10 percent of this nuclear reactor
is this type.
There are two types of reactors that are not currently popular but may become important
in the future.
Gas-cooled reactors were developed by atomic scientists in the United Kingdom.
Carbon dioxide serves as a coolant for a graphite-moderated core. As in the heavy-water
reactor, natural isotopic mixtures of uranium are used as a fuel. However, this is not a
popular type of reactor. China is the only country that plans to build one in the near future.
Nuclear breeder reactors are nuclear fission reactors that form new nuclear fuel as they
operate to produce electricity. Because the process requires fast- moving neutrons, water
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cannot be used as a moderator because it slows the neutrons too much and most models
of breeder reactors function without a moderator. Because it is necessary to move heat
away from the reactor core very efficiently, most breeder reactors use liquid metal (often
liquid sodium) as a core coolant. Thus, they are often called liquid metal fast- breeder
reactors. When a fast-moving neutron hits a non-fissionable uranium-238 (U-238) nucleus
and is absorbed, an atom of fissionable plutonium-239 (Pu-239) is produced. Remember
that U-235 is a nuclear fuel and U-238 is not. Thus, a breeder reactor converts a nonfuel
(U-238) into a fuel (Pu-239).
During the early stages of the development of nuclear power plants, breeder reactors
were seen as the logical step after nuclear fission development because they would
reduce the need for uranium, which is a nonrenewable material. However, most breeder
reactors are considered experimental and because they produce plutonium-239, which
can be used to produce nuclear weapons, they are politically sensitive. Most countries
have discontinued their breeder reactor programs following accidents or political
decisions. The United Kingdom. Germany, the United States, and France have breeder
reactors that are currently not in operation. Russia, China, India, and Japan have
operating breeder reactors, and India is currently building a new breeder reactor.
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The nuclear fuel cycle consists of mining and processing uranium, generating
nuclear power through controlled fission, reprocessing spent fuel, disposing of
nuclear waste, and decommissioning power plants. Each part of the cycle is
associated with characteristic processes, all with different potential environmental
problems.
The present burner reactors (mostly light-water reactors) use uranium-235 as a
fuel. Uranium is a nonrenewable resource mined from the Earth. If many more
burner reactors were constructed, we would face fuel shortages. Nuclear energy
based on burning uranium-235 in light-water reactors is thus not sustainable. For
nuclear energy to be sustainable, safe, and economical, we will need to develop
breeder reactors.
Radioisotopes affect the environment in two major ways: by emitting radiation that
affects other materials, and by entering ecological food chains.
Major environmental pathways by which radiation reaches people include uptake
by fish ingested by people, uptake by crops ingested by people, inhalation from
air, and exposure to nuclear waste and the natural environment.
The dose response for radiation is fairly well established. We know the dose–
response for higher exposures, when illness or death occurs. However, there are
vigorous de- bates about the health effects of low-level exposure to radiation and
what relationships exist between exposure and cancer. Most scientists believe
that radiation can cause cancer. But, Ironically, radiation can be used to kill cancer
cells, as in radiotherapy treatments.
We have learned from accidents at nuclear power plants that it is difficult to plan
for the human factor. People make mistakes. We have also learned that we are
not as prepared for accidents as we would like to think. Some believe that people
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are not ready for the responsibility of nuclear power. Others believe that we can
design much safer power plants where serious accidents are impossible.
Transuranic nuclear waste is now being disposed of in salt beds—the first disposal
of radioactive waste in the geologic environment in the United States.
There is a consensus that high-level nuclear waste may be safely disposed of in
the geologic environment. The problem has been to locate a site that is safe and
not objectionable to the people who make the decisions and to those who live in
the region.
Nuclear power is again being seriously evaluated as an alternative to fossil fuels.
On the one hand, it has ad- vantages: It emits no carbon dioxide, will not contribute
to global warming or cause acid rain, and can be used to produce alternative fuels
such as hydrogen. On the other hand, people are uncomfortable with nuclear
power because of waste-disposal problems and possible accidents.
Lesson 5: Renewable and sustainable energy resources
Alternative and Renewable Energy
Because of these looming threats to the reserves of the conventional source of energy:
fossil fuel, some possible substitutes are being considered. This has led to the rise of a
number of alternative energy sources. While the viability of each can be argued, they all
contribute something positive when compared to fossil fuels: lower emissions, lower fuel
prices and the reduction of pollution and possibly less disturbance to biodiversity
compared to how fossil fuels are extracted.
Here are eleven of the most prominent alternative fuel sources and the benefits they offer
and potential for increased uptake in the coming years.
a. Solar Power - When most people think of alternative energy sources, they tend
to use solar power as an example. The technology has evolved massively over
the years and is now used for large-scale energy production and power generation
for single homes.
This energy source is completely renewable and the costs of installation are
outweighed by the money saved in energy bills from traditional suppliers.
Nevertheless, solar cells are prone to deterioration over large periods of time and
are not as effective in unideal weather conditions.
b. Hydroelectric method is some of the earliest means of creating energy, though
its use began to decline with the rise of fossil fuels. Despite this, it still accounts
for approximately seven percent of the energy produced in the United States.
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Hydroelectric energy carries with it a number of benefits. Not only is it a clean
source of energy, which means it doesn’t create pollution and the myriad issues
that arise from it, but it is also a renewable energy source. Better yet, it also offers
a number of secondary benefits that are not immediately apparent. The dams
used in generating hydroelectric power also contribute to flood control and
irrigation techniques.
c. Wave - Water again proves itself to be a valuable contributor to alternative energy
fuel sources with wave energy converters. These hold an advantage over tidal
energy sources because they can be placed in the ocean in various situations and
locations.
Much like with tidal energy, the benefits come in the lack of waste produced. It is
also more reliable than many other forms of alternative energy and has enormous
potential when used properly.
Again, the cost of such systems is a major contributing factor to slow uptake. We
also don’t yet have enough data to find out how wave energy converters affect
natural ecosystems.
d. Biofuels In contrast to biomass energy sources, biofuels make use of animal and
plant life to create energy. In essence they are fuels that can be obtained from
some form of organic matter.
They are renewable in cases where plants are used, as these can be regrown on
a yearly basis. However, they do require dedicated machinery for extraction, which
can contribute to increased emissions even if biofuels themselves don’t. Biofuels
are increasingly being adopted, particularly in the United States. They accounted
for approximately seven percent of transport fuel consumption as of 2012.
e. Natural gas sources have been in use for a number of decades, but it is through
the progression of compression techniques that it is becoming a more viable
alternative energy source. In particular, it is being used in cars to reduce carbon
emissions. Demand for this energy source has been increasing. In 2016, the lower
48 states of the United States reached record levels of demand and consumption.
Despite this, natural gas does come with some issues. The potential for
contamination is larger than with other alternative fuel sources and natural gas still
emits greenhouse gases, even if the amount is lower than with fossil fuels.
f.
Geothermal power is about extracting energy from the ground around us. It is
growing increasingly popular, with the sector as a whole experiencing five percent
growth in 2015.
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The World Bank currently estimates that around forty countries could meet most
of their power demands using geothermal power.
This power source has massive potential while doing little to disrupt the land.
However, the heavy upfront costs of creating geothermal power plants has led to
slower adoption than may have been expected for a fuel source with so much
promise.
This form of energy generation has become increasingly popular in recent years.
It offers much the same benefits that many other alternative fuel sources do in that
it makes use of a renewable source and generates no waste.
g. Wind Energy Current wind energy installations power roughly twenty million
homes in the United States per year and that number is growing. Most states in
the nation now have some form of wind energy set-up and investment into the
technology continues to grow.
Unfortunately, this form of energy generation also presents challenges. Wind
turbines restrict views and may be dangerous to some forms of wildlife.
h. Biomass energy comes in a number of forms. Burning wood has been used for
thousands of years to create heat, but more recent advancements have also seen
waste, such as that in landfills, and alcohol products used for similar purposes.
Focusing on burning wood, the heat generated can be equivalent to that of a
central heating system. Furthermore, the costs involved tend to be lower and the
amount of carbon released by this kind of fuel falls below the amount released by
fossil fuels.
However, there are a number of issues that you need to consider with these
systems, especially if installed in the home. Maintenance can be a factor, plus you
may need to acquire permission from a local authority to install one.
i.
Tidal Energy uses the power of water to generate energy, much like with
hydroelectric methods but its application has more in common with wind
turbines in many cases.
Though it is a fairly new technology, its potential is enormous. A report produced
in the United Kingdom estimated that tidal energy could meet as much as 20% of
the UK’s current electricity demands.
j.
Hydrogen Energy Unlike other forms of natural gas, hydrogen is a completely
clean burning fuel. Once produced, hydrogen gas cells emit only water vapor and
warm air when in use. The major issue with this form of alternative energy is that
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it is mostly derived from the use of natural gas and fossil fuels. As such, it could
be argued that the emissions created to extract it counteract the benefits of its
use.
The process of electrolysis, which is essential for the splitting of water into
hydrogen and oxygen, makes this less of an issue. However, electrolysis still ranks
below the previously mentioned methods for obtaining hydrogen, though research
continues to make it more efficient and cost-effective.
Almost all alternative energy source are renewable (at least shorter time to regenerate
compared to fossil fuel). However, not all can be considered as sustainable and green.
Being categorized as sustainable and green entails a difference in either production and
extraction.
Activity:
1. Cite an example of alternative energy that is not sustainable? Why do you think
so?
Resources:
1. https://study.com/academy/lesson/what-is-the-green-revolution-definitionbenefits-and-issues.html
2. https://courses.lumenlearning.com/geophysical/chapter/distribution-of-earthswater/
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Module 07:
Global and Regional Environmental Problems: Causes, Interconnections, and
Proposed Solutions
Time Frame: 3 Weeks (Week 15-17)
Overview:
Lesson 1: Water pollution
a. Case study: India’s Ganges River: Religion, poverty and health
Lesson 2: Air pollution
a. Case study: Mexico City: Urban air pollution
Lesson 3: Solid and hazardous waste
a. Case study 1: Solid waste production in the United States,
b. Case study 2: Hazardous wastes in Bhopal, India
Lesson 4: Deforestation
a. Case study 1: The Philippines
Lesson 5: Biodiversity loss
a. Case study: Costa Rica
Lesson 6: Global Climate Change
Lesson 7: Stratospheric Ozone Depletion
Lesson 8: The Concept of Sustainable Development
General Objectives:
1. Have an overview of the different environmental issues in the present world.
2. Have an overview of the concept of sustainable development
3. Describe environmental impacts of globalization.
4. Recognize the central role energy use has on environmental problems.
5. List the major sources of water pollution.
6. Describe the various methods of waste disposal and the problems associated with each
method.
7. Innovate Approaches to Solid Waste Problems
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Lesson 1: Water Pollution
Lesson Objectives
1. Identify ways how can you conserve water
2. Define water pollution.
3. Analyze sources and effects of water pollution
4. Enumerate the importance of sewage treatment and clean water in developing
countries
5. Evaluate ways of how we control water pollution
Water is essential for life. It is the medium in which all living processes occur. Water
dissolves nutrients and distributes them to cells, regulates body temperature, supports
cells, and removes waste products. We are 60 percent water. We could survive for weeks
without food but only a few days without water.
There are different issues concerning water but for the purpose of this discussion, we will
be focusing on water pollution.
A. Sources of Water Pollution
Water pollution is any physical, biological, or chemical change in water quality that
adversely affects living organisms or makes water unsuitable for desired uses, can be
considered pollution. There are natural sources of water contamination, such as poison
springs, oil seeps, and sedimentation from erosion, and human - caused changes that
affect water quality or usability.
1. Pollution includes point sources and nonpoint sources
Pollution-control standards and regulations usually distinguish between point and
nonpoint pollution sources. Factories, power plants, sewage treatment plants,
underground coal mines, and oil wells are classified as point sources because they
discharge pollution from specific locations, such as drainpipes, ditches, or sewer outfalls.
These sources are discrete and identifiable, so they are relatively easy to monitor and
regulate. It is generally possible to divert effluent from the waste streams of these sources
and treat it before it enters the environment.
In contrast, nonpoint sources of water pollution are diffuse, having no specific location
where they discharge into a particular body of water. They are much harder to monitor
and regulate than point sources because their origins are hard to identify. Nonpoint
sources include runoff from farm fields and feedlots, golf courses, lawns and gardens,
construction sites, logging areas, roads, streets, and parking lots. While point sources
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may be fairly uniform and predictable throughout the year, nonpoint sources are often
highly episodic. The first heavy rainfall after a dry period may flush high concentrations of
gasoline, lead, oil, and rubber residues off city streets, for instance, while subsequent
runoff may be much cleaner.
2. Biological pollution: pathogens and waste
Although the types, sources, and effects of water pollutants are often interrelated, it is
convenient to divide them into major categories for discussion. Here, we look at some of
the important sources and effects of different pollutants.
a. Pathogens - The most serious water pollutants in terms of human health
worldwide are pathogenic (disease-causing) organisms. Among the most
important waterborne diseases are typhoid, cholera, bacterial and amoebic
dysentery, enteritis, polio, infectious hepatitis, and schistosomiasis. Malaria,
yellow fever, and filariasis are transmitted by insects that have aquatic larvae.
Altogether, at least 25 million deaths each year are blamed on water - related
diseases. Nearly two-thirds of the mortalities of children under 5 years old in
poorer countries are linked to these diseases.
The main source of these pathogens is untreated or improperly treated human
wastes. Animal wastes from feedlots or fields near waterways and foodprocessing factories with inadequate waste treatment facilities also are sources of
disease-causing organisms.
In developed countries, sewage treatment plants and other pollution-control
techniques have reduced or eliminated most of the worst sources of pathogens in
inland surface waters. Furthermore, drinking water is generally disinfected by
chlorination, so epidemics of waterborne diseases are rare in these countries. The
United Nations estimates that 90 percent of the people in developed countries
have adequate (safe) sewage disposal, and 95 percent have clean drinking water.
The situation is quite different in less-developed countries, where billions of people
lack adequate sanitation and access to clean drinking water. Conditions are
especially bad in remote, rural areas, where sewage treatment is usually primitive
or nonexistent and purified water is either unavailable or too expensive to obtain.
The World Health Organization estimates that 80 percent of all sickness and
disease in less-developed countries can be attributed to waterborne infectious
agents and inadequate sanitation.
b. Biological Oxygen Demand - The amount of oxygen dissolved in water is a good
indicator of water quality and of the kinds of life it will support. An oxygen content
above 6 parts per million (ppm) will support game fish and other desirable forms
of aquatic life. At oxygen levels below 2 ppm, water will support mainly worms,
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bacteria, fungi, and other detritus feeders and decomposers. Oxygen is added to
water by diffusion from the air, especially when turbulence and mixing rates are
high, and by photosynthesis of green plants, algae, and cyanobacteria. Turbulent,
rapidly flowing water is constantly aerated, so it often recovers quickly from
oxygen-depleting processes. Oxygen is removed from water by respiration and
chemical processes that consume oxygen. Because oxygen is so important in
water, dissolved oxygen (DO) levels are often measured to compare water quality
in different places.
Adding organic materials, such as sewage or paper pulp, to water stimulates
activity and oxygen consumption by decomposers. Consequently, biochemical
oxygen demand (BOD), or the amount of dissolved oxygen consumed by aquatic
microorganisms, is another standard measure of water contamination.
Alternatively, chemical oxygen demand (COD) is a measure of all organic matter
in water.
Downstream from a point source, such as a municipal sewage plant discharge, a
characteristic decline and restoration of water quality can be detected either by
measuring DO content or by observing the types of flora and fauna that live in
successive sections of the river. The oxygen decline downstream is called the
oxygen sag. Upstream from the pollution source, oxygen levels support normal
populations of clean-water organisms. Immediately below the source of pollution,
oxygen levels begin to fall as decomposers metabolize waste materials. Rough
fish, such as carp, bullheads, and gar, are able to survive in this oxygen-poor
environment, where they eat both decomposer organisms and the waste itself.
Farther downstream, the water may become so oxygen depleted that only the
most resistant microorganisms and invertebrates can survive. Eventually, most of
the nutrients are used up, decomposer populations are smaller, and the water
becomes oxygenated once again. Depending on the volumes and flow rates of
the effluent plume and the river receiving it, normal communities may not appear
for several miles downstream.
3. Nutrients cause eutrophication
Water clarity (transparency) is affected by sediments, chemicals, and the
abundance of plankton organisms; clarity is a useful measure of water quality and
water pollution. Rivers and lakes that have clear water and low biological
productivity are said to be oligotrophic (oligo = little + trophic = nutrition). By
contrast, eutrophic waters are rich in organisms and organic materials.
Eutrophication, an increase in nutrient levels and biological productivity, often
accompanies successional changes in lakes. Tributary streams bring in sediments
and nutrients that stimulate plant growth. Over time, ponds and lakes often fill in,
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becoming marshes or even terrestrial biomes. The rate of eutrophication depends
on water chemistry and depth, volume of inflow, mineral content of the surrounding
watershed, and biota of the lake itself.
Human activities can greatly accelerate eutrophication, an effect called cultural
eutrophication. Cultural eutrophication is caused mainly by increased nutrient
input into a water body. Increased productivity in an aquatic system sometimes
can be beneficial. Fish and other desirable species may grow faster, providing a
welcome food source. Often, however, eutrophication produces “blooms” of algae
or thick growths of aquatic plants stimulated by elevated phosphorus or nitrogen
levels. Bacterial populations then increase, fed by larger amounts of organic
matter. The water often becomes cloudy, or turbid, and has unpleasant tastes and
odors. Cultural eutrophication can accelerate the “aging” of a water body
enormously over natural rates. Lakes and reservoirs that normally might exist for
hundreds or thousands of years can be filled in a matter of decades.
Eutrophication also occurs in marine ecosystems, especially in nearshore waters
and partially enclosed bays or estuaries.
Case Study 1: The Ganges River of India
Brief background of the issue: Water is absolutely essential for the basic
sustenance of human being. Most of the civilizations have come up on the banks of
rivers or in the river valleys. India is no exception. In India every city has come up on
the bank of a major river. Total water available in the world is 1,400,000 cubic km.
However, 96.5 percent of it is there in the oceans and only 1.7 percent is ground
water, 1.7 percent is in glaciers and .01 percent is in the atmosphere in the form of
water vapor.
The religion: In India which prevalently practices Hinduism, believes that goddesses
are part of their geographical landscape. This includes the Ganges. The Ganges
River, is known to them as Ma Ganga (or Mother Ganges). It flows from the glaciers
of the Himalayas and crosses much of the subcontinent before flowing into the Indian
Ocean. The religious origins of this goddess are varied, and devotees of different
Hindu gods often believe in different stories about her. One of the more common
stories comes from followers of the god Shiva. Many Shiva devotees believe Mother
Ganges offered to descend to earth to purify the burning coals of the ancestors of
the Hindu sage Bhagiratha. However, she was concerned that her fall from the
cosmic realm would destroy the earth, so Shiva offered to catch her in his hair. Her
waters ran in rivulets through his hair and onto the earth, where she purified the
remains.
The Ganges River is therefore not only a waterway, but a goddess from heaven.
Thus, many Hindus believe that the river has incredible healing powers. It is a
common belief that bathing in the Ganges washes away a person’s bad karma and
is like being in heaven. Some Hindus even believe that being brushed by a breeze
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which contains a single drop of the Ganges will absolve the impurities of multiple
lifetimes. To most Hindus, dying in the holy city of Varanasi, on the banks of the
Ganges, is said to result in moksha—a release from the endless cycle of suffering
and rebirth. It is estimated that 32,000 corpses are cremated each year in Varanasi,
after which their ashes are given to the Ganges. Others who cannot afford cremation
simply wrap and float the body down the river. To access her healing waters, Hindus
travel from all over the world on pilgrimages, often filling containers with water to
bring back to their homes for rituals or healings. In fact, the largest gathering of
human beings in the entire world regularly occurs on the banks of the river at the city
of Allahabad. Every 12 years, the city hosts the Kumbh Mela, a religious festival
during which the central ritual is bathing in the Ganges to achieve moksha. In 2001,
over 30 million pilgrims attended, making it the largest gathering in human history.
The Geopolitics: In the Indian Sub-continent, 30 percent of the major Himalayan
rivers are biologically dead for fishing and usage for human consumption. Increasing
population aggravates the per capita water availability. In 1951 water availability in
India was 5177 m3/person per year, which was reduced to 1342 m 3/person per year
by 2000. With rise in population since year 2000 it became worse. Shortage of water
and its centrality caused major social and geopolitical stresses. India’s neighbors:
Pakistan, China and Bangladesh, are having their own problems due to water
scarcity. Since water resources of Indian Sub-continent are monolithic in nature, the
shortage has its own international ramifications.
The situation: The Ganges river flows through 100 cities with populations over
100,000, and 97 cities and 48 towns with populations between 50,000 to 100,000. A
large proportion of sewage water with higher organic load in the Ganges is from this
population through domestic water usage. Because of the establishment of a large
number of industrial cities on the bank of the Ganges countless tanneries, chemical
plants, textile mills, distilleries, slaughterhouses, and hospitals prosper and grow
along this and contribute to the pollution of the Ganges by dumping untreated waste
into it. One coal-based power plant on the banks of the Pandu River, a Ganges
tributary near the city of Kanpur, burns 600,000 tons of coal each year and produces
210,000 tons of fly ash.
The ash is dumped into ponds from which a slurry is filtered, mixed with domestic
wastewater, and then released into the Pandu River. Fly ash contains toxic heavy
metals such as lead and copper. The amount of parts per million of copper released
in the Pandu before it even reaches the Ganges is thousand times higher than what
is there in the uncontaminated water
Unfortunately, the river has also become one of the most polluted bodies of water in
the entire world, due to India’s exploding population and rapid industrialization. Over
450 million people live in the Ganges river basin, and human waste is the cause of
most of the pollution. Almost five billion liters of sewage flow into the river every day,
only a quarter of which is treated. By Varanasi, the Ganges is an open sewer. Fecal
bacteria at this point is 150 times higher than the safe level for bathing, let alone
drinking. Over 300,000 Indian children die annually from drinking contaminated
water. Industrial effluent also pollutes the river, particularly from tanneries in Kanpur.
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Indian industries dump nearly a billion liters of waste into the river daily.5 Climate
change has worsened the problem: water flow has decreased as Himalayan glaciers
shrink.
For many Hindus, this is unacceptable. Illnesses and deaths have become common,
and many Hindus will not drink or bathe in the river—an important part of their faith—
due to the toxic waters. Many Hindus have called for serious efforts to clean the
Ganges. Hindu holy man Chidanand Saraswati has said that India is “killing its own
mother.” Narendra Modi, a Hindu nationalist elected prime minister in 2014, ran on
religious pledges to restore the purity of the Ganges. Modi even claimed divine
intervention in his election. In his victory speech, given on the Ganges in Varanasi,
he stated: “Ma Ganga has called me… she decided some responsibilities for me. Ma
Ganga is screaming for help, she is saying I hope one of my sons gets me out of this
filth… it has been decided by God for me to serve Ma Ganga.” Modi has since
pledged $3 billion dollars over five years for river clean-up and promised to use Hindu
holy men as project advisors. However, most analysts agree the funds are not nearly
enough to fix the problems on the 2,500-km long river. There is also another issue:
not all Hindus believe cleanup is needed In fact, many Hindus continue to bathe in
or even drink the Ganges regularly. Confident in the healing powers of the divine
river, they believe nothing could compromise the purity of their goddess. For them,
Mother Ganges exists to wash away the impurities and pollution of earth and thus
can cleanse herself.
Major cleanup efforts are thus a waste of money and effort. Some governments and
industries have taken advantage of these beliefs, and have used confidence in the
cleansing power of the Ganges to justify continuing to pollute the river. Other Hindus
acknowledge the problem, but lay blame on Muslims. Because cattle are holy to
many Hindus, Kanpur’s polluting tanneries—which create leather from cowhides—
are all owned by Muslims. Many Muslims claim that they have been unfairly
persecuted by Hindu nationalists, who they say would rather persecute Muslim
businesses than address more expensive sewage issues.
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The Resolution: In March 2017, as cleanup efforts continued to fail, the High Court
of Uttarakhand state confirmed the deified status that Hindus have long given the
river. They issued a judgment that the Ganges and the Yamuna river—a Ganges
tributary—are “living entities” which are entitled to human rights. Those caught
polluting the river could thus be charged with assault or even murder. A few days
later, activists sought murder charges against several politicians on behalf of the
Yamuna River, sections of which are no longer able to support life. However, on July
7, 2017, the Supreme Court of India struck down Uttarakhand state’s ruling, arguing
that treating the rivers as living entities was impractical.
The Ganges is still revered as a living goddess by Hindus across the world, but an
effective solution to its pollution remains elusive.
Activity:
1. Choose any body of water in the Philippines which you deemed to be polluted.
2. Identify the issues that contributes to the pollution in that body of water.
3. Identify the areas/locations/sectors which are affected by this polluted body of
water.
4. Enumerate ways on how you can start to revive it and make it a functional.
Lesson 2: Air Pollution
Air pollution is the presence of chemicals in the atmosphere in concentrations high
enough to harm organisms, ecosystems, or materials, or to alter climate. The effects of
air pollution range from annoying to lethal.
Air pollutants come from natural and human sources. Natural sources include dust blown
by wind pollutants from wildfires and volcanic eruptions, and volatile organic chemicals
released by some plants.
Most natural air pollutants are spread out over the globe or removed by chemical cycles,
precipitation, and gravity. However, chemicals emitted from volcanic eruptions (Figure 152) and some natural forest fires can reach harmful levels.
Human inputs of outdoor air pollutants occur mostly in industrialized and urban areas
where people, motor vehicles, and factories are concentrated. Most of these pollutants
enter the atmosphere from the burning of coal in power and industrial plants (stationary
sources, and gasoline and diesel fuel in motor vehicles (mobile sources).
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Scientists classify outdoor air pollutants into two categories. Primary pollutants are
harmful chemicals emitted directly into the air from natural processes and human
activities. While in the atmosphere, some primary pollutants may react with one another
or with the basic components of air to form new harmful chemicals, called secondary
pollutants.
Figure no. 15 -2
Basic Pollutants include the following:
1. Carbon Oxides: Carbon monoxide (CO) is a colorless, odorless, and highly toxic gas
that forms, during the in- complete combustion of carbon-containing materials. Major
sources are motor vehicle exhaust, clearing and burning of forests and grasslands,
tobacco smoke, and cooking with open fires and inefficient stoves.
CO reacts with hemoglobin in red blood cells and re- duces the ability of blood to
transport oxygen to body cells and tissues. Chronic exposure can trigger heart attacks
and aggravate lung diseases such as asthma and emphysema. At high levels, CO
causes headache, nausea, drowsiness, mental impairment, collapse, coma, and
death.
2. Carbon dioxide (CO2) is a colorless, odorless gas. About 93% of the CO2 in the
atmosphere is the result of the natural carbon cycle. The rest comes from human
activities, mostly burning fossil fuels and clearing forests and grasslands. Emissions
from human activities have been rising sharply since the industrial revolution.
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Increasing levels of CO2 can contribute to warming of the atmosphere and global
climate change.
3.
Nitrogen Oxides and Nitric Acid. Nitrogen oxide (NO) is a colorless gas that forms
when nitrogen and oxygen gas in air react at the high-combustion temperatures in
automobile engines and coal-burning power plants. Lightning and certain bacteria in
soil and water also produce NO as part of the nitrogen cycle.
In the air, NO reacts with oxygen to form nitrogen dioxide (NO2), a reddish-brown
gas. Collectively, NO and NO2 are called nitrogen oxides (NOx). Some of the NO2
reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) —
components of acid deposition. Both NO and NO 2 play a role in the formation of
photochemical smog – a mix of chemicals formed under the influence of sunlight in
cities with heavy traffic. Nitrous oxide (N 2O), a greenhouse gas, is emitted from
fertilizers and animals wastes and is produced by burning fossil fuels.
Nitrogen oxides can irritate the eyes, nose, and throat, aggravate lung ailments such
as asthma and bronchitis, suppress plant growth, and reduce visibility.
4.
Sulfur Dioxide and Sulfuric Acid. Sulfur dioxide (SO2) is a colorless gas with an
irritating odor. About one-third of the SO2 in the atmosphere comes from natural
sources as part of the sulfur cycle. The other two-thirds (and as much as 90% in
urban areas) come from human sources, mostly combustion of sulfur-containing coal
in electric power and industrial plants and from oil refining and smelting of sulfide
ores.
In the atmosphere, SO2 can be converted to microscopic suspended droplets of
sulfuric acid (H2SO4) and suspended particles of sulfate (SO42) salts that return to the
earth as a component of acid deposition. These pollutants also reduce visibility and
aggravate breathing problems. SO2 and H2SO4 can damage crops, trees, soils, and
aquatic life in lakes. They can corrode metals and damage paint, paper, leather, and
stone on buildings and statues.
5.
Particulates. Suspended particulate matter (SPM) consists of a variety of solid
particles and liquid droplets small and light enough to remain suspended in the air for
long periods. About 62% of the SPM in outdoor air comes from natural sources such
as dust, wild fires, and sea salt. The remaining 38% comes from human sources such
as plowed fields, road construction, un- paved roads, tobacco smoke, coal-burning
electric power and industrial plants, and motor vehicles.
Particulate matter is a pollutant of special concern. Many studies have demonstrated
a direct relationship between exposure to PM and negative health impacts. Smallerdiameter particles (PM2.5 or smaller) are generally more dangerous and ultrafine
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particles (one micron in diameter or less) can penetrate tissues and organs, posing
an even greater risk of systemic health impacts.
These particles can irritate the nose and throat, damage the lungs, aggravate asthma
and bronchitis, and shorten life. Toxic particulates (such as lead, cadmium, and
PCBs) can cause mutations, reproductive problems, and cancer. Toxic lead particles
mostly from burning coal and leaded gasoline and smelting lead ores can accumulate
in the body and cause nervous system damage, mental retardation (especially in
children), and digestive and other health problems. In the United States, particulate
air pollution is responsible for about 60,000 premature deaths a year, according to
the EPA and the Harvard School of Public Health. Particulates also reduce visibility,
corrode metals, and discolor clothes and paints.
6. Ozone. Ozone (O3), a colorless and highly reactive gas, is a major component of
photochemical smog. It can cause coughing and breathing problems, aggravate lung
and heart diseases, reduce resistance to colds and pneumonia, and irritate the eyes,
nose, and throat. It also damages plants, rubber in tires, fabrics, and paints.
7. Volatile Organic Compounds (VOCs). Organic com-pounds that exist as gases in the
atmosphere are called volatile organic compounds (VOCs). Most are hydrocarbons,
such as isoprene (C3H8) and terpenes like C10H15 emitted by the leaves of many
plants, and methane (CH4, a greenhouse gas). About a third of global methane
emissions come from natural sources, mostly plants, wetlands, and termites. The rest
comes from human sources—primarily rice paddies, landfills, and oil and natural gas
wells—and from cows (from belching and flatulence). Other VOCs, including benzene,
vinyl chloride, and trichloroethylene (TCE), are used as industrial solvents, drycleaning fluids, and components of gasoline, plastics, drugs, synthetic rubber, and
other products.
8. Radioactive Radon (Rn). Radon-222 is a naturally occurring colorless and odorless
radioactive gas found in some types of soil and rock. It can seep into homes and
buildings sitting above such deposits. Long-term exposure can cause lung cancer,
especially among smokers.
Air pollution kills an estimated seven million people worldwide every year. WHO data
shows that 9 out of 10 people breathe air containing high levels of pollutants. WHO is
working with countries to monitor air pollution and improve air quality.
From smog hanging over cities to smoke inside the home, air pollution poses a
major threat to health and climate. The combined effects of ambient (outdoor) and
household air pollution cause about seven million premature deaths every year, largely
as a result of increased mortality from stroke, heart disease, chronic obstructive
pulmonary disease, lung cancer and acute respiratory infections.
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More than 80% of people living in urban areas that monitor air pollution are exposed to
air quality levels that exceed WHO guideline limits, with low- and middle-income countries
suffering from the highest exposures, both indoors and outdoors.
From smog hanging over cities to smoke inside the home, air pollution poses a major
threat to health and climate. Ambient air pollution accounts for an estimated 4.2 million
deaths per year due to stroke, heart disease, lung cancer and chronic respiratory
diseases.
Policies and investments supporting cleaner transport, energy-efficient housing, power
generation, industry and better municipal waste management can effectively reduce key
sources of ambient air pollution.
Indoor air pollution
Indoor air pollution is considered by experts to be a higher-risk human health problem
than outdoor air pollution. Some indoor air pollutants come from out- doors. But chemicals
used or produced inside buildings in developed areas can be dangerous pollutants, as
can smoke from poorly designed wood or coal stoves used to provide heat and cook food
in many developing countries.
Household air pollution is one of the leading causes of disease and premature death in
the developing world.
Exposure to smoke from cooking fires causes 3.8 million premature deaths each year,
mostly in low- and middle-income countries. Burning fuels such as dung, wood and coal
in inefficient stoves or open hearths produces a variety of health-damaging pollutants,
including particulate matter (PM), methane, carbon monoxide, polyaromatic
hydrocarbons (PAH) and volatile organic compounds (VOC). Burning kerosene in simple
wick lamps also produces significant emissions of fine particles and other pollutants.
Exposure to indoor air pollutants can lead to a wide range of adverse health outcomes in
both children and adults, from respiratory illnesses to cancer to eye problems. Members
of households that rely on polluting fuels and devices also suffer a higher risk of burns,
poisonings, musculoskeletal injuries and accidents.
Air quality is closely linked to earth’s climate and ecosystems globally. Many of the drivers
of air pollution (i.e. combustion of fossil fuels) are also sources of high CO 2 emissions.
Policies to reduce air pollution, therefore, offer a “win–win” strategy for both climate and
health, lowering the burden of disease attributable to air pollution, as well as contributing
to the near- and long-term mitigation of climate change.
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Case Study 2: The Polluted Air of Mexico City
With 19.5 million people (2019), Mexico City is one of the world’s megacities and will soon
become a hypercity with more than 20 million people. More than one-third of its residents
live in slums called barrios or in squatter settlements that lack running water and
electricity. At least 3 million people in the barrios have no sewage facilities, so human
waste from these slums is deposited in gutters, vacant lots, and open ditches every day,
attracting rats and flies. When the winds pick up dried excrement, a fecal snow blankets
parts of the city. This bacteria-laden fallout leads to widespread salmonella and hepatitis
infections, especially among children.
Mexico City has one of the world’s worst air pollution problems because of a combination
of too many cars, polluting factories, a sunny climate and thus more smog (see photo on
the left), and topographical bad luck. The city sits in a bowl-shaped valley surrounded on
three sides by mountains—conditions that trap air pollutants at ground level. Breathing its
air is said to be roughly equivalent to smoking three packs of cigarettes per day.
The city’s air and water pollution cause an estimated 100,000 premature deaths per year.
That it was named “Makesicko City.”
Some progress has been made. The percentage of days each year in which air pollution
standards are violated has fallen from 50% to 20%. The city government has banned cars
in its central zone, required catalytic converters on all cars made after 1991, phased out
use of leaded gasoline, and replaced old buses, taxis, and delivery vehicles with cleaner
ones. The city also bought land for use as green space and planted more than 25 million
trees to help absorb pollutants.
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In 1992, the United Nations named Mexico City “the most polluted city on the planet.”
Since then Mexico City has made progress in reducing the severity of some of its air
pollution problems. In 2013, the Institute for Transportation and Development awarded
Mexico City its Sustainable Transportation Award for expanding its bus rapid transit
system, rebuilding its public parks, reducing crime, and expanding its bike sharing
program and its bike lanes. The percentage of days each year in which air pollution
standards are violated has fallen from 50% to 20% and ozone and other air pollutants are
now at about the same level as those of Los Angeles, California.
The city government has moved refineries and factories out of the city, banned cars in its
central zone, and required air pollution controls on all cars made after 1991. It has also
phased out the use of leaded gasoline, expanded public transportation, and replaced
some old buses, taxis, and delivery trucks with vehicles that produce fewer emissions.
Mexico City still has a long way to go as its human population increases along with its
number of motor vehicles. However, this story shows what can be done to improve
environmental quality once a community decides to act.
Activity:
1. In your own ways, what can you do to lessen the air pollution in your area?
Lesson 3: Solid and Hazardous Waste
A. Solid Waste
Resources are vital to people, and the standard of living increases with their availability
in useful forms. Indeed, the availability of resources is one measure of a society’s wealth.
Those who have been most successful in locating and extracting or importing and using
resources have grown and prospered. Without resources to grow food, construct buildings
and roads, and manufacture everything from computers to televisions to automobiles,
modern technological civilization as we know it would not be possible. For example, to
maintain our standard of living in the United States, each person requires about 10 tons
of nonfuel minerals per year. We use other resources, such as food and water, in much
greater amounts.
During the first century of the Industrial Revolution, the volume of waste produced in the
United States was relatively small and could be managed using the concept of “dilute and
disperse.” Factories were located near rivers because the water provided a number of
benefits, including easy transport of materials by boat, enough water for processing and
cooling, and easy disposal of waste into the river. With few factories and a sparse
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population, dilute and disperse was sufficient to remove the waste from the immediate
environment.
As industrial and urban areas expanded, the concept of dilute and disperse became
inadequate, and a new concept, “concentrate and contain,” came into use. It has become apparent, however, that containment was, and is, not always achieved. Containers,
whether simple trenches excavated in the ground or metal drums and tanks, may leak or
break and allow waste to escape. Health hazards resulting from past waste-disposal
practices have led to the present situation, in which many people have little confidence in
government or industry to preserve and protect public health.
In many parts of the world, people are facing a serious solid-waste disposal problem.
Basically, we are producing a great deal of waste and don’t have enough acceptable
space for disposing of it. It has been estimated that within the next few years most cities
will run out of landfill space. To say we are actually running out of space for land-fills isn’t
altogether accurate—land used for landfills is minute compared to the land area of some
countries. Rather, existing sites are being filled, and it is difficult to site new landfills. After
all, no one wants to live near a waste-disposal site, be it a sanitary landfill for municipal
waste, an incinerator that burns urban waste, or a hazardous-waste disposal operation
for chemical materials. This attitude is widely known as NIMBY (“not in my backyard”).
Of particular importance to waste management is the growing awareness that many of
our waste-management programs involve moving waste from one site to another, not
really managing it. For example, waste from urban areas may be placed in landfills; but
eventually these land-fills may cause new problems by producing methane gas or noxious
liquids that leak from the site and contaminate the surrounding areas.
The economic boom in the 1950s lead to an increase in the amount of trash – and litter –
being produced by Americans due to the growing popularity of single use items. However,
it was not long until people began to realize the environmental impact humans were
having on the Earth’s eco-system. During the early 1970’s US federal government formed
the Environmental Protection Agency (EPA). Around the same time as the formation of
the EPA came the passing of the Resource Recovery Act by Congress. This bill was
created with the intention of shifting both federal and community attention to the practices
of recycling, resource recovery and the conversion of wastes into energy., and the 3 R’s
was born
3R’s, which stands reduce reuse, recycle apparently was not sufficient as man continue
to extract resources and dispose them at the rate greater than they were extracted.
Others believe that the environmentally correct concept with regards to waste generation
and waste management is to consider wastes as resources that is just out of place.
Although we may not soon be able to reuse and recycle all waste, it seems apparent that
the increasing cost of raw materials, energy, transportation, and land will make it
financially feasible to reuse and recycle more resources and products. Moving toward this
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objective is moving toward an environmental view that there is no such thing as waste.
Under this concept, waste would not exist because it would not be produced—or, if
produced, would be a resource to be used again.
Another thinking, referred to as the “zero waste” movement also known as industrial
ecology, helps us study the relationships among industrial systems and their links to
natural systems. Under the principles of industrial ecology, our industrial society would
function much as a natural ecosystem function. Waste from one part of the system would
be a resource for another part.
Until recently, zero waste production was considered unreasonable in the wastemanagement arena. However, it is catching on. A large part of the planning involves
taxing waste in all its various forms, from smokestack emissions to solids delivered to
landfills. Already, in the Netherlands, pollution taxes have nearly eliminated discharges of
heavy metals into waterways. At the household level, the government is considering
programs—known as “pay as you throw”—that would charge people by the volume of
waste they produce. Taxing waste, including household waste, motivates people to
produce less of it.
And eventually, 3R’s were not enough and more and more R’s were added until it became
7 R’s – Rethink, Refuse, Reduce, Repurpose, Reuse, Recycle and Rot. But this thinking
still allows us the provision for waste which is what we are trying to eliminate, not just
reduce.
And so came the idea of Cradle to Cradle (C2C). It is a design that is an eye-opening
approach to eliminating waste and creating a circular economy. Developed by William
McDonough and Dr. Michael Braungart, the main focus of is to design products that are
100% beneficial to people and the environment – that really improve quality of life, rather
than merely doing less harm.
Many companies have already stepped forward, demonstrating that for-profit entities can
successfully implement the concept. Most of the products we use today follow a cradleto-grave mentality of “use it, lose it and bury it in the ground.” Cradle to Cradle, however,
implies that the end of a product’s use cycle will be followed by the beginning of another
– ad infinitum.
C2C starts in the design phase: Designers must consider how every piece of a product
can retain value at the end of its current use cycle. But that’s not all: It should also make
some kind of positive impact. Whereas traditional products are designed to do less
damage (but not fully avoid it), the C2C mentality asks “How can this product do good?”
Real innovations that follow the C2C approach include buildings with roofs that can be
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used for farming, carpets that filter particles from the air and wall plaster that absorbs
airborne toxins.
C2C points the way to finally diverging from the “take-make-waste” path that is causing
our planet to suffer. Instead of patching the system with down-cycling and so-called
“sustainable” solutions, we need a zero-waste approach with C2C design and a
truly circular economy.
Companies – particularly product designers, manufacturers and architects – are called to
stand up and design goods that, when no longer useful, can safely return their “nutrients”
to industry and mother earth.
In sum, previous notions of waste disposal are no longer acceptable, and we are
rethinking how we deal with materials, with the objective of eliminating the concept of
waste entirely. In this way, we can reduce the consumption of minerals and other virgin
materials, which depletes our environment, and live within our environment more.
Case Study 3: Solid Waste in the United States
United States is one of the countries which produce a lot of trash. In 1960, the average American
generated 2.7 pounds (1.2 kg) of Municipal Solid Waste (MSW) per day. In 2012, each of them
generated an average of 4.4 pounds (2 kg) of such waste per day. The total MSW that year was
251 million tons (230 million metric tons)—enough waste to fill 95,000 garbage trucks each day.
The total generation of municipal solid waste in 2017 was 267.8 million tons of MSW,
approximately 5.7 million tons more than the amount generated in 2015 (shown in the figure
below). MSW generated in 2017 increased to 4.51 pounds per person per day. This is an
increase from the 262.1 million tons generated in 2015 and the 208.3 million tons in 1990.
EPA began collecting and reporting data on the generation and disposition of waste in the United
States more than 30 years ago. The Agency uses this information to measure the success of
materials management programs across the country and to characterize the national waste
stream.
The total generation of municipal solid waste (MSW) in 2017 was 267.8 million tons (U.S. short
tons, unless specified) or 4.51 pounds per person per day. Of the MSW generated,
approximately 67 million tons were recycled and 27 million tons were composted. Together,
more than 94 million tons of MSW were recycled and composted, equivalent to a 35.2 percent
recycling and composting rate. In addition, more than 34 million tons of MSW (12.7 percent)
were combusted with energy recovery and more than 139 million tons of MSW (52.1 percent)
were landfilled.
EPA refers to trash, or MSW, as various items consumers throw away after they are used. These
items include bottles and corrugated boxes, food, grass clippings, sofas, computers, tires and
refrigerators. However, MSW does not include everything that is landfilled in MSW, or
nonhazardous, landfills, such as construction and demolition (C&D) debris, municipal
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wastewater sludge, and other non-hazardous industrial wastes. While the analysis in Facts and
Figures focuses primarily on MSW, EPA has been including estimates of C&D generation and
recovery in recent years.
In 2017, the amount of MSW generated was 267.8 million tons. The amount of MSW recycled
was 67.2 million tons and the amount composted was 27 million tons. The amount of MSW
combusted with energy recovery was 34 million tons, while the amount of MSW sent to landfills
was 139.6 million tons. Presented below are details of these trends:
•
Over the last few decades, the generation, recycling and disposal of MSW has changed
substantially. Generation of MSW increased (except in recession years) from 88.1
million tons in 1960 to 267.8 million tons in 2017. Generation decreased 1 percent
between 2005 and 2010, followed by a rise in generation of 7 percent from 2010 to
2017.
•
The generation rate in 1960 was just 2.68 pounds per person per day. It increased to
3.66 pounds per person per day in 1980. In 2000, it reached 4.74 pounds per person
per day and then decreased to 4.69 pounds per person per day in 2005. The generation
rate was 4.51 pounds per person per day in 2017, which was one of the lowest
generation rates since 1990.
•
Over time, recycling rates have increased from just over 6 percent of MSW generated
in 1960 to about 10 percent in 1980, to 16 percent in 1990, to about 29 percent in 2000,
and to over 35 percent in 2017.
•
The amount of MSW combusted with energy recovery increased from zero in 1960 to
14 percent in 1990. In 2017, it was over 12 percent.
•
The disposal of waste to landfills has decreased from 94 percent of the amount
generated in 1960 to about 52 percent of the amount generated in 2017
https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/national-overview-facts-and-figures-materials
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B. Hazardous Waste
Hazardous waste is a waste with properties that make it dangerous or capable of having
a harmful effect on human health or the environment. Hazardous waste is generated from
many sources, ranging from industrial manufacturing process wastes to batteries and may
come in many forms, including liquids, solids gases, and sludges.
In order for a material to be classified as a hazardous waste, it must first be a solid waste.
Once it has been classified as a solid waste, the second step is to examine whether or
not the waste is specifically excluded from regulation as a solid or hazardous waste. Once
a generator determines that their waste meets the definition of a solid waste, they
investigate whether or not the waste is a listed or characteristic hazardous waste.
Electronic waste or e-waste consists of discarded television sets, cell phones, computers,
e-toys, and other electronic devices. It is the fastest-growing solid waste problem in the
United States and in the world. Each year, Americans discard an estimated 155 million
cell phones, 250 million personal computers, and many more millions of television sets,
iPods, Blackberries, and other electronic products.
Most e-waste ends up in landfills and incinerators. It includes high-quality plastics and
valuable metals such as aluminum, copper, nickel, platinum, silver, and gold. The
concentration of copper in e-waste, for instance, is much higher than in currently mined
copper ores. E-waste is also a source of toxic and hazardous pollutants, including
polyvinylchloride (PVC), brominated flame retardants, lead, and mercury, which can
contaminate air, surface water, groundwater, and soil.
According to a 2005 report by the Basel Action Network, about 50–80% of U.S. e-waste
is shipped to China, India, Pakistan, Nigeria, and other developing countries where labor
is cheap and environmental regulations are weak. Workers there, many of whom are
underage, rip these products to pieces to recover valuable metals like copper and gold
and reusable parts and re often times exposed to the toxic metals. The remaining scrap
is dumped in waterways and fields or burned in open fires, exposing many people to toxic
dioxins.
Transfer of hazardous waste from developed to developing countries is banned by the
International Basel Convention, which the United States has refused to ratify. The
European Union (EU) has led the way in dealing with e-waste. In a cradle-to-grave
approach, it requires manufacturers to take back electronic products at the end of their
useful lives for repair, remanufacture, or recycling, and e-waste is banned from landfills
and incinerators. Japan is also adopting cradle-to- grave standards for electronic devices
and appliances.
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The United States produces roughly half of the world’s e-waste and recycles only about
10% of it, but that is changing. In 2000, Massachusetts became the first U.S. state to ban
the disposal of computers and TV sets in landfills and incinerators, and five other states
have established similar regulations. Some electronics manufacturers including Apple,
Intel, Hewlett-Packard, Dell, Sharp, Panasonic, and Sony have free recycling programs.
Some will arrange for pickups or pay shipping costs. A growing consumer awareness of
the problem has spawned highly profitable e- cycling businesses. And, nonprofit groups,
such as Free Geek in Portland, Oregon, are motivating many people to donate, recycle,
and reuse old electronic devices.
But e-recycling and reuse probably will not keep up with the explosive growth of e-waste.
According to Jim Puckett, coordinator of the Basel Action Network, the only real long-term
solution is a prevention approach that gets toxic materials out of electrical and electronic
products by using green design. For ex- ample, Sony Electronics has eliminated toxic
lead solder used to attach electronic parts together and has also removed potentially
hazardous flame retardants from virtually all of its electronic products. The company has
replaced old cathode ray tubes (which contain large quantities of toxic lead) used in
televisions and computers with liquid crystal displays, which are more energy efficient and
contain few hazardous materials. Electronic waste is just one of many types of solid and
hazardous waste discussed in this lesson.
Case Study 4: Hazardous Waste: Bhopal India Incident
In 1984, an accident at the Union Carbide Corporation (UCC) chemical plant in Bhopal, India,
caused a massive toxic gas leak which released more than 40 tons of methyl isocyanate, an
extremely toxic gas. The company is American owned but Indian government has a 22% stake
in the company’s subsidiary known as Union Carbide India Limited (UCIL). An estimated
600,000 people in communities surrounding the plant were exposed to the deadly fumes. Within
days, more than 5,000 people died, and more than 10,000 subsequently died from gas-related
diseases. At least 50,000 people suffered various degrees of visual impairment, respiratory
problems, and other injuries from the exposure, and many more have experienced chronic
illnesses related to the disaster. To date, the tragic events in Bhopal have been the world’s worst
industrial disaster.
An Indian investigation of the accident found that the disaster likely happened because Union
Carbide officials had scaled back safety and alarm systems at the plant in order to cut costs.
Ironically, most of the deaths and injuries could have been avoided if people had known that
methyl isocyanate is highly soluble in water, that a wet towel over the head would have greatly
reduced one’s exposure, and that showers would have alleviated aftereffects. Unfortunately,
neither the people affected nor the medical authorities involved had any idea of what chemical
they confronted, much less the way to protect or treat themselves.
The toxic plume had barely cleared when, on December 7 (of the same year as the leak
incident), the first multi-billion-dollar lawsuit was filed by an American attorney in a U.S. court.
This was the beginning of years of legal machinations in which the ethical implications of the
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tragedy and its effects on Bhopal's people were largely ignored. In March 1985, the Indian
government enacted the Bhopal Gas Leak Disaster Act as a way of ensuring that claims arising
from the accident would be dealt with speedily and equitably. The Act made the government the
sole representative of the victims in legal proceedings both within and outside India. Eventually
all cases were taken out of the U.S. legal system under the ruling of the presiding American
judge and placed entirely under Indian jurisdiction much to the detriment of the injured parties.
Estimates of the death toll vary from as few as 3,800 to as many as 16,000, but government
figures now refer to an estimate of 15,000 killed over the years. Toxic material remains, and 30
years later, many of those who were exposed to the gas have given birth to physically and
mentally disabled children. For decades, survivors have been fighting to have the site cleaned
up, but they say the efforts were slowed when Michigan-based Dow Chemical took over Union
Carbide in 2001. Human rights groups say that thousands of tons of hazardous waste remain
buried underground, and the government has conceded the area is contaminated. There has,
however, been no long-term epidemiological research which conclusively proves that birth
defects are directly related to the drinking of the contaminated water.
In a settlement mediated by the Indian Supreme Court, UCC accepted moral responsibility and
agreed to pay $470 million to the Indian government to be distributed to claimants as a full and
final settlement. The figure was partly based on the disputed claim that only 3000 people died
and 102,000 suffered permanent disabilities. Upon announcing this settlement, shares of UCC
rose $2 per share or 7% in value. By the end of October 2003, according to the Bhopal Gas
Tragedy Relief and Rehabilitation Department, compensation had been awarded to 554,895
people for injuries received and 15,310 survivors of those killed.
Following the events of December 3 1984 environmental awareness and activism in India
increased significantly. The Environment Protection Act was passed in 1986, creating the
Ministry of Environment and Forests (MoEF) and strengthening India's commitment to the
environment. Under the new act, the MoEF was given overall responsibility for administering
and enforcing environmental laws and policies. It established the importance of integrating
environmental strategies into all industrial development plans for the country. However, despite
greater government commitment to protect public health, forests, and wildlife, policies geared
to developing the country's economy have taken precedence in the last 20 years
Activity:
1.
If you have the opportunity and the capability to buy any gadgets you want, what
will be your considerations and how often would you buy? Why?
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Lesson 4: Deforestation
Deforestation
Deforestation is believed to have increased erosion and caused the loss of an estimated
562 million hectares (1.4 billion acres) of soil worldwide, with an estimated annual loss of
5–6 million hectares. Cutting forests in one country affects other countries. For example,
Nepal, one of the most mountainous countries in the world, lost more than half its forest
cover between 1950 and 1980. This destabilized soil, increasing the frequency of
landslides, amount of runoff, and sediment load in streams. Many Nepalese streams feed
rivers that flow into India. Heavy flooding in India’s Ganges Valley has caused about a
billion dollars’ worth of property damage a year and is blamed on the loss of large forested
watersheds in Nepal and other countries. Nepal continues to lose forest cover at a rate of
about 100,000 hectares (247,000 acres) per year. Reforestation efforts replace less than
15,000 hectares (37,050 acres) per year. If present trends continue, little forestland will
remain in Nepal, thus permanently exacerbating India’s flood problems.
Because forests cover large, often remote areas that are little visited or studied,
information is lacking on which to determine whether the world’s forestlands are
expanding or shrinking, and precisely how fast and how much. Some experts argue that
there is a worldwide net increase in forests because large areas in the temperate zone,
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such as the eastern and midwestern United States, were cleared in the 19 th and early
20th centuries and are now regenerating. Only recently have programs begun to obtain
accurate estimates of the distribution and abundance of forests, and these suggest that
past assessments overestimated forest biomass by 100 to 400%. On balance, we believe
that the best estimates are those suggesting that the rate of deforestation in the 21st
century is 7.3 million hectares a year—an annual loss equal to the size of Panama. The
good news is that this is 18% less than the average annual loss of 8.9 million hectares in
the 1990s.
History of Deforestation
Forests were cut in the Near East, Greece, and the Roman Empire before the modern
era. Removal of forests continued northward in Europe as civilization advanced. Fossil
records suggest that prehistoric farmers in Denmark cleared forests so extensively that
early-successional weeds occupied large areas. In medieval times, Great Britain’s forests
were cut, and many forested areas were eliminated. With colonization of the New World,
much of North America was cleared. The greatest losses in the present century have
taken place in South America, where 4.3 million acres have been lost on average per year
since 2000. Many of these forests are in the tropics, mountain regions, or high latitudes,
places difficult to exploit before the advent of modern transportation and machines. The
problem is especially severe in the tropics because of rapid human population growth.
Satellite images provide a new way to detect deforestation.
Causes of Deforestation
Historically, the two most common reasons people cut forests are to clear land for
agriculture and settlement and to use or sell timber for lumber, paper products, or fuel.
Logging by large timber companies and local cutting by villagers are both major causes
of deforestation. Agriculture is a principal cause of deforestation in Nepal and Brazil and
was one of the major reasons for clearing forests in New England during the first
settlement by Europeans. A more subtle cause of the loss of forests is indirect
deforestation—the death of trees from pollution or disease
If global warming occurs as projected by global climate models, indirect forest damage
might occur over large regions, with major die-offs in many areas and major shifts in the
areas of potential growth for each species of tree due to altered combinations of
temperature and rainfall.25 The extent of this effect is controversial. Some suggest that
global warming would merely change the location of forests, not their total area or
production. However, even if a climate conducive to forest growth were to move to new
locations, trees would have to reach these areas. This would take time because changes
in the geographic distribution of trees depend primarily on seeds blown by the wind or
carried by animals. In addition, for production to remain as high as it is now, climates that
meet the needs of forest trees would have to occur where the soils also meet these needs.
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This combination of climate and soils occurs widely now but might become scarcer with
large-scale climate change.
Deforestation affects the people and animals where trees are cut, as well as the wider
world. Some 250 million people living in forest and savannah areas depend on them for
subsistence and income—many of them among the world’s rural poor. Eighty percent of
Earth’s land animals and plants live in forests, and deforestation threatens species
including the orangutan, Sumatran tiger, and many species of birds. Removing trees
deprives the forest of portions of its canopy, which blocks the sun’s rays during the day
and retains heat at night. That disruption leads to more extreme temperature swings that
can be harmful to plants and animals.
Yet the effects of deforestation reach much farther. The South American rainforest, for
example, influences regional and perhaps even global water cycles, and it's key to the
water supply in Brazilian cities and neighboring countries. The Amazon actually helps
furnish water to some of the soy farmers and beef ranchers who are clearing the forest.
The loss of clean water and biodiversity from all forests could have many other effects
we can’t foresee, touching even your morning cup of coffee.
In terms of climate change, cutting trees both adds carbon dioxide to the air and
removes the ability to absorb existing carbon dioxide. If tropical deforestation were a
country, according to the World Resources Institute, it would rank third in carbon
dioxide-equivalent emissions, behind China and the U.S.
If deforestation and mismanaged forest clearing continues, such a massive loss of forest
would be felt on a global scale. Protecting the Amazon is often hyped as one of the most
effective ways to mitigate the effect of climate change. The ecosystem absorbs millions
of tons of carbon emissions every year. When those trees are cut or burned, they not
only release the carbon they were storing, but a tool to absorb carbon emissions
disappears.
Case Study 5: Deforestation in the Philippines
The Philippines is one of the most severely deforested countries in the tropics and most
deforestation has happened in the last 40 years. Estimates place forest cover in the Philippines
in the year 1900 at 21 million hectares, covering 70 % of the total land area. By 1999, forests
covered 5.5 million hectares; only 800,000 hectares of this was primary forest. As illegal logging
continues, the remaining forest is endangered.
The destruction of the Philippine forest was the subject of a recent study (1999), Decline of the
Philippine Forest, by the Institute of Environmental Science for Social Change (ESSC). This
study traces the history of the decline, examines the causes and effects of deforestation, and
discusses emerging perspectives. The study considers two possible Philippine scenarios for the
year 2010. One assumes that meaningful steps will be taken to reverse the decline and offers
some hope; the other scenario assumes that things will continue as in the past, and the outcome
will be a continued national degradation of resources.
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The Philippines is paying a high price for the destruction of its forests and a number of major
problems confronting the nation can be traced directly to deforestation. Today, the country faces
food insecurity due to soil erosion, which means depleted nutrients and low crop yield. In many
provinces, at least 50% of the topsoil has been lost, and 70% of all croplands are vulnerable to
erosion. The country’s climatic conditions are such that typhoons sweep the country an average
of 19 times a year. The topography is mainly uplands with a slope equal to or greater than 18%
and these areas make up 52% of total land area. In the absence of forest cover and with frequent
heavy typhoon rains, soil erosion, mass wasting, and landslides are induced.
The Philippines is facing water insecurity because of degraded and poorly managed
watersheds. More than 57 % of the major watersheds are critically denuded, which means loss
of water infiltration and slow recharging of water tables. Nationwide, water quality has
deteriorated and cities like Manila, Cebu, Davao, and Baguio, are constantly facing water
shortages. A country that once exported some of the finest woods in the world is now a net wood
importer.
The decimation of the forest is a tragedy for indigenous peoples. Ethnic groups become forced
to retreat into the interior and further impoverished. Government is doing little to raise these
people above their subsistence level. Some have left their lands, and the sight of indigenous
peoples begging in city streets is not uncommon. They have lost their lands, and their culture
has been degraded. With the destruction of indigenous cultures, the nation is losing a treasure
that should be nurtured to enrich national cultural diversity.
This loss of cultural communities is closely linked to the loss of biodiversity. Tropical forests are
rich in herbs, woody plants, birds, insects, and animal life. Destroying the forests means
destroying the myriad creatures and flora on which the indigenous communities depend. Forest
loss also means loss of forest products such as, rattan, resins, and gums, a source of livelihood
for indigenous people. Wildlife is quickly disappearing and to date, the destruction of the
ecosystems is taking a heavy toll on biodiversity: 18 species of fauna are already rare and
endangered, while 43 species of birds are threatened with extinction.
The ESSC’s response to these problems is multifaceted and flexible. However, in any approach,
community management is central. This approach was discussed at such international
conferences as the 1996 FAO Conference in Bangkok, the Intergovernmental Forum on Forests
in New York in February 2000 (through the Working Group on Community Involvement in Forest
Management), and at the World Bank Forest Policy Implementation Review and Strategy in
Singapore in April 2000. A presentation on the role of indigenous peoples in watershed
management was delivered to the House of Representatives of the Philippine Congress in
December 1999.
ESSC is the Secretariat of the Philippine Working Group (PWG) for national resource
management. PWG activities are documented in the ESSC publication, Forest People Facing
Change. This monograph gives a history of the PWG, discusses the philosophy guiding its
approach, examines PWG strengths and weaknesses, documents field visits, and critiques
PWG findings. PWG members represent a wide variety of disciplines and backgrounds;
expertise is drawn from the academe, government, NGOs, and funding agencies. Each member
is there in his/her own capacity and not as a representative of an agency. Members feel free to
discuss, question, and examine any problem without being held responsible for what others
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have said in the past or the present limitations of policy. Starting in the outlying sitios, where
marginalized communities live, the group works its way up through the municipal to the
provincial level. The PWG, after witnessing how government policies are being implemented,
has been effective in having the national government modify its policies.
To promote community based forest and resource management, ESSC developed community
mapping to ensure community participation and the articulation of community views and
concerns. How this works is explained in the book Community Mapping Manual for Resource
Management, published in conjunction with the DENR. Apart from enabling communities to
present their own views, it introduces indigenous communities to modern technology and basic
scientific knowledge. Another manual for trainers is being prepared.
For ESSC, the relationship between culture and ecosystems is of critical importance and this
relationship is discussed in three publications: Philippine Culture and Ecosystems, Resource
Conflict and Cultural Management in Southern Sierra Madre, and Mindoro in the Balance.
ESSC promotes community-based forest management (CBFM) and assisted natural
regeneration (ANR). While CBFM has been successful over the past years, the present
leadership of the Department of Environment and Natural Resources (DENR) seems more
interested in experimenting with timber corridors. However, it does not make much sense to cut
regenerating scrublands and then to replant the area with alien species when the condition of
the scrublands can be improved by ANR.
In the Philippines, the promotion of CBFM, especially in degraded watershed areas, is
imperative. People living in watersheds have a stake in improving them, and by so doing,
contribute significantly to solving the water problem of the agricultural lowland communities and
of our cities.
*Environmental Science for Social Change, 2011
Activity:
1. List 3 ways on how you can help lessen the impact of deforestation in our country.
2. How do you plan to execute each way?
Lesson 5: Biodiversity Loss
Scientific value comes from our need to have living things available so we can learn basic
laws of nature, the way ecosystems function, and the way the world works generally.
Societies have long held that such “pure science” is valuable. Many scientists are
engaged in this endeavor by sheer curiosity about the world, including about the
functioning of individual types of organisms. Realistically, though, most of the science
done with these species aims for more pragmatic goals—new medicines, protection from
gene loss in agriculture and forestry, and other outcomes already discussed in previous
topics.
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A Cautionary Note. The use of wild species and biodiversity for instrumental value can
raise some problems of justice as we navigate the needs of people with competing claims.
For example, while the rosy periwinkle was a success story because of its effectiveness
in combating cancer, little of the money returned to Madagascar, a very poor country. In
other cases, such as the case of turmeric (a spice commonly used in India), ancient herbal
remedies have been patented by large companies. While the patent on turmeric was
eventually overturned, the patent on the rosy periwinkle was not, and money from the
rosy periwinkle came to Madagascar only when the patent ran out. The indigenous people
in the areas where biodiversity is highest may not be the ones to benefit from their
resources. The Nagoya Protocol on Access and Benefit Sharing is a recent international
treaty designed to protect the interests of indigenous peoples as products are discovered
in wild sources.
Similarly, ecotourism may bring money to poor areas of the world, but such tourism can
also increase pollution, directly harm wildlife, or alter local societies in negative ways. For
example, whale-watching boats on the St. Lawrence River disrupt the feeding of whales.
Tourist boats on Mexican lakes frighten flocks of flamingoes and reduce their feeding
time. Popular bird song apps for smart phones can distract birds so much that chicks may
not get enough food from their parents. Ecotourism can marginalize indigenous people
as part of the scenery, or they can remain poor while tourism operators gain wealth.
Nonetheless, there is sustainable tourism, and people intending to travel in the hopes of
promoting conservation can find tourism that is done well.
The Loss of Instrumental Value. Overall, a loss of biodiversity has a tremendous
negative effect on the world in real, practical ways. The Economics of Ecosystems and
Biodiversity (TEEB) report, released in May 2008, was the first international report to
detail the economic and life-quality effects of biodiversity loss. Researchers have shown
that the costs of the loss of biodiversity are higher for the world’s poorest people. In fact,
continued loss of biological diversity could halve the income of the poorest billion and a
half people. One example of this loss of income occurred after a massive coral bleaching
event in the Indian Ocean in 1998. It is estimated that the loss of food, jobs, tourism, and
coastal protection will cost a total of $8 billion by 2018. Because the people who benefit
most from the rapid use of resources are not the people who are most harmed by the loss
of those resources, many ethicists believe such an outcome to be morally wrong. Thus,
even the instrumental values of Earth’s resources have an ethical component.
Biodiversity is described as the variety of life on Earth. We can be more specific than that.
The dimensions of biodiversity include the genetic diversity within a species and the
variety of species as well as the range of communities and ecosystems. When scientists
use the term biodiversity, however, sometimes they mean a characteristic that they can
calculate and compare between habitats. In this definition, scientists use two measures
to calculate biodiversity—the number of species and a measure of how “even” the species
are. A habitat has low biodiversity if it is dominated by only one species, with few members
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of other species, because those few might easily leave or die out. Given the same number
of species, diversity is considered to be higher in habitats where the dominance by any
single species is low. Recall that over long periods of time, natural selection leads to
speciation (the creation of new species) as well as extinction (the disappearance of
species). Now, we are interested in how humans interact with wild species and impact
biodiversity over a relatively short time.
How Many Species are there?
Almost 2 million species have been discovered and described, and certainly many more
than that exist. Most people are completely unaware of the great diversity of species that
occurs within any given taxonomic category. Groups especially rich in species are the
flowering plants (about 224,000 species) and the insects (about 950,000 species), but
even less- diverse groups, such as birds or ferns, are rich with species that are unknown
to most people. Groups that are conspicuous or commercially important—such as birds,
mammals, fish, and trees—are much more fully explored and described than insects and
very small organisms, such as soil nematodes, fungi, and bacteria. Taxonomists are
aware that their work in finding and describing new species is incomplete. Estimates of
unknown species keep rising as taxonomists explore more ecosystems. Whatever the
number of species, the planet’s biodiversity represents an amazing and diverse
storehouse of biological wealth.
The Decline of Biodiversity
Biodiversity is declining in the United States as well as around the world. Because U.S.
ecosystems are well studied, the trends that show themselves here (including the decline
of many plant and animal species) may represent larger global trends. Endemic species
(those found in only one habitat and nowhere else) are especially at risk. Some areas of
the country and of the world are particularly vulnerable to species loss. These areas are
often the focus of special conservation efforts.
North America. The biota of the United States is as well known as any. Even so, not
much is known about most of the 200,000-plus species of plants, animals, and microbes
estimated to live in the nation. At least 500 species native to the United States, including
at least 100 vertebrates, are known to have gone extinct (or have “gone missing” and are
believed to have gone extinct) since the early days of colonization. An inventory of 20,897
wild plant and animal species in the 50 states, carried out in the late 1990s by a team of
biologists from the Nature Conservancy and the National Heritage Network concluded
that one-third are vulnerable (threatened), imperiled (endangered), or already extinct. In
the United States, mussels, crayfish, fishes, and amphibians—all species that depend on
freshwater habitats—are at greatest risk. In part, this potential for loss stems from the
high number of endemic aquatic species in the American Southeast. For example, there
are close to 200 species of freshwater mussels and clams in North America, giving these
bivalves the greatest species diversity of any freshwater bivalve group in the world.
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Flowering plants are also of great concern, with one-third of their numbers in decline in
North America.
Species populations are a more important element of biodiversity than even the species’
existence. Populations of species that occupy different habitats and ranges contribute to
biological wealth, as they provide goods and services important in ecosystems. Across
North America, even populations of well-studied species are in decline. Commercial
landings of many species of fish are down, puzzling reductions in amphibian populations
are occurring all over the world, and many North American songbird species (such as the
cerulean warbler, wood thrush, and scarlet tanager) are declining and have disappeared
entirely from some locations. Other migratory groups have also suffered declines. By
2014, the precipitous 90% decline of monarch butterflies had made them world news, as
they struggled to survive loss of habitat and exposure to chemicals.
Global Outlook.
Worldwide, the loss of biodiversity is even more disturbing. One thorough analysis of
biodiversity is the Global Biodiversity Outlook, published by the United Nations. From their
2010 assessment, shows groups from a comprehensive survey of more than 47,000
species, categorized by level of risk of extinction. The 2014 Global Biodiversity
Assessment 4 did not include the same analyses, but the trends were the same.
Estimates of extinction rates in the past show alarming increases in loss of species. For
mammals, the background (past) extinction rate was less than one extinction every
thousand years, although rates were higher during five great extinction events. (Scientists
estimate the background extinction rate from the fossil record of marine animals and from
rates of change in DNA.) This rate can be compared with known extinctions of the past
several hundred years (for mammals and birds, 20 to 25 species per hundred years and,
for all groups, 850 species over about 500 years), indicating that the current rate of
extinction is 100 to 1,000 times higher than past rates.
The International Union for Conservation of Nature (IUCN) keeps a running list of
threatened species. In 2014, approximately 32% (2,030) of amphibian species, 22%
(1,199) of mammal species, and 13% (1,373) of bird species were globally threatened.
The majority of threatened species are concentrated in the tropics, where biodiversity is
so rich as to be almost unimaginable. Biologist Edward O. Wilson identified 43 species of
ants on a single tree in a Peruvian rain forest, a level of diversity equal to the entire ant
fauna of the British Isles. Other scientists found 300 species of trees in a 1-hectare (2.5acre) plot and almost 1,000 species of beetles on 19 specimens of a species of tree in
Panama. Unfortunately, the same tropical forests that hold such high biodiversity are also
experiencing the highest rate of deforestation. Because the inventory of species in these
ecosystems is so incomplete, it is virtually impossible to assess extinction rates in such
forests. This uncertainty may contain a kernel of good news. Some scientists believe that
we are overestimating the total number of species, and as a result, overestimating
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extinction rates in the areas where most habitat is being lost. No one knows exactly how
many species are becoming extinct, but the loss is real, and species loss represents a
continuing depletion of the biodiversity of our planet.
Reasons for the Decline
The most famous extinction in American history was that of the passenger pigeon
(Ectopistes migratorius), once the most common bird in North America. In the early and
mid-1800s, the population of this bird was estimated at 3-5 million, but market hunting
caused a rapid decline. By the end of that century, the wild population was gone; the last
know wild bird was shot in 1900. The last passenger pigeon in captivity died in the
Cincinnati Zoo in 1914. How could such a widespread creature go extinct so quickly?
In the distant past, extinctions were largely the result of processes such as climate
change, plate tectonics, and even asteroid impacts. Current threats to biodiversity are
sometimes described with the acronym HIPPO, which refers to five factors: habitat
destruction, invasive species, pollution, population, and overexploitation. Many declining
species experience combinations of several or all of these factors. Indeed, global climate
change in particular increases the effects of some of these factors. Future losses will be
greatest in the developing world, where biodiversity is greatest and human population
growth is highest. Africa and Asia have lost almost two-thirds of their original natural
habitat. People’s desire for a better way of life, the desperate poverty of rural populations,
and the global market for timber and other natural resources are powerful forces that will
continue to draw down biological wealth on those continents.
One key to slowing the loss of biodiversity lies in bringing human population growth down.
If the human population increases to 10 billion, as some demographers believe that it will,
the consequences for the natural world may be frightening. Another key is to pull
individual consumption down to sustainable levels in parts of the world with high
consumption of energy and materials. These two concepts will be vital to solving several
environmental issues
The five current threats to biodiversity that make up the acronym HIPPO.
1. HABITAT DESTRUCTION. By far the greatest threat to biodiversity is the physical
alteration of habitats through the processes of conversion, fragmentation, simplification,
and intrusion. Habitat destruction has already been responsible for 36% of the known
extinctions and is the key factor in the currently observed population declines. Natural
species are adapted to specific habitats, so if the habitat changes or is eliminated, the
species go with it.
a. Conversion. Natural areas are commonly converted to farms, housing subdivisions,
shopping malls, marinas, and industrial centers. When a forest is cleared, for example,
destruction of the trees is not the only result; every other plant or animal that occupied
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the destroyed ecosystem, either permanently or temporarily (e.g., migrating birds), also
suffers. Global forest cover has been reduced by 40% already, and the decline continues.
Agriculture already occupies 38% of land on Earth; croplands that replace natural habitats
are quite inhospitable to all but a few species that tend to be well adapted to the new
managed landscapes.
b. Fragmentation. Natural landscapes generally have large patches of habitat that are
well connected to other similar patches. Human-dominated landscapes, however, consist
of a mosaic of different land uses, resulting in small, often geometrically configured
patches that frequently contrast highly with neighboring patches. Small fragments of
habitat can support only small numbers and populations of species, making them
vulnerable to extermination. Species that require large areas are the first to go; those that
grow slowly or have naturally unstable populations are also vulnerable.
Reducing the size of a habitat creates a greater proportion of edges—breaks between
habitats that expose species to predators. Increased edge favors some species but may
be detrimental to others. Edges also favor species that prey on nests, such as crows,
magpies, and jays. These predators are thought to be partly responsible for declines in
many neotropical bird populations.
Roadways offer particular dangers to wildlife. The number of animals killed on roadways
now far exceeds the number killed by hunters. As rural areas are developed, the
increasing numbers of animals found on roadways are a serious hazard to motorists. With
4.1 million miles (6.6 million km) of paved roadways in the United States, more than a million animals a day become roadkill. Overpasses and tunnels are increasingly being built
to provide wildlife with safe corridors. A 2008 study at Purdue University identified
amphibians as especially affected by road mortality. More than 95% of the roadkill that
researchers identified over 11 months along a stretch of road in the Midwest were
amphibians.
c. Simplification. Human use of habitats often simplifies them. Removing fallen logs
and dead trees from woodlands for firewood, for example, diminishes an important microhabitat on which species ranging from woodpeckers to germinating forest trees depend.
When a forest is managed for the production of one (or a few) species of tree, tree
diversity declines, and as a result, so does the diversity of the plant and animal species
that depend on the less favored trees. Streams are sometimes channelized—their beds
are cleared of fallen trees and stony riffle areas (places with more rapidly moving water),
and sometimes the stream is straightened out by dredging the bottom. Such alterations
inevitably reduce the diversity of fish and invertebrates that live in the stream.
d. Intrusion. Birds use the air as a highway, especially as they migrate north and south
in the spring and fall. The clear surfaces of windows are one of the greatest dangers for
birds, especially when the windows are lit from behind and birds are flying at night.
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Ornithologist Daniel Klem estimated that between 100 million and 1 billion birds die every
year from crashing into glass windows.
Recently, telecommunications towers have presented a new hazard to birds. Although
television towers have been around for decades, new towers are sprouting up on hilltops
and in countryside in profusion. Cell phone signal towers are also common. The lights
often placed on these towers can attract birds, which usually migrate at night, and the
birds simply collide with the towers and supporting wires. In 2000, a study estimated that
the towers kill somewhere between 5 to 50 million birds a year.
Birds are just one example of organisms harmed by the intrusion of structures into
habitats. Any solution to wild species’ decline must include creative ways to lower the
impact of human structures on other organisms. Three organizations petitioned the
Federal Communications Commission (FCC) to incorporate bird mortality in its decisions
about new towers in 2002, but nothing was done. In 2008, a federal appeal court finally
ruled that the FCC did in fact have to come up with a plan to protect birds. A 2011 federal
policy provided hope that there would be an agreement to make towers more bird friendly.
2. INVASIVE SPECIES. An exotic, or alien, species is one that is introduced into an
area from somewhere else, often a different continent. Because the species is not native
to the new area, it is frequently unsuccessful in establishing a viable population and
quietly disappears. Such is the fate of many pet birds, reptiles, and fish that escape or are
deliberately released. Some exotic species establish populations that remain at low levels
without becoming pests. Occasionally, however, an alien species finds the new
environment to be very favorable, and it becomes an invasive species thriving,
spreading out, and perhaps eliminating native species by predation or competition for
space or food. Most of the insect pests and plant parasites that plague agricultural
production were accidentally introduced. Invasive species are major agents in driving
native species to extinction and are responsible for an estimated 39% of all animal
extinctions since 1600.
a. Accidental Introductions. As humans traveled around the globe in the days of
sailing ships and exploration, they brought with them more than curiosity and dreams of
exotic lands. They brought rats and mice to ports all over the world. As a result, rats are
the most invasive mammal worldwide. The two most common invasive rat species are the
black rat (Rattus rattus, called the ship rat) and the brown rat (Rattus norvegicus, called
the Norway rat). Rats also eat crops, destroy property, and cause other harm to humans,
but their effect on other species is profound. In terms of species loss, the arrival of rats is
especially deadly to birds. According to one report, rats have been found preying on
nearly one-quarter of sea-bird species. Thirty percent of seabirds are threatened with
extinction, and rats are the biggest single cause.
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Rats are not the only example of accidental introduction of non-native species. The red
imported fire ant (Solenopsis invicta), arrived in Mobile, Alabama, from South America,
possibly in shipments of wood. The fire ant is a major pest across the southern United
States, inflicting damage to crops and domestic animals. It also contributes to the decline
of wild species. In Texas, it is estimated that fire ants kill a fifth of songbird babies before
they leave the nest.
b. Deliberately Introduced . . . Deliberate introductions sanctioned by the U.S. Natural
Resources Conservation Service (in the interest of “reclaiming” eroded or degraded
lands) have brought us kudzu and other runaway plants, such as the autumn olive and
multiflora rose. Salt cedar was introduced in the American Southwest for erosion control
and has taken over riverbanks there. Many other exotic plants are introduced as
horticultural desirables. Fallopia japonica, Japanese knotweed, is a good example. Tall,
with attractive flowers, it originated in Asia and is now found in North America and Europe.
It forms dense patches and outcompetes native plants. Unfortunately, its strong
underground stem (rhizome) and root system cause the plant to spread even when it does
not produce seeds.
There are specific instances of both deliberate and accidental introductions in
aquaculture—the farming of shellfish, seaweed, and fish—which produces one-third of
all seafood consumed worldwide. Parasites, seaweeds, invertebrates, and pathogens
have been introduced together with the desired aquaculture species, often escaping from
the pens or ponds and entering the sea or nearby river system. Sometimes the
aquaculture species itself is a problem. Atlantic salmon, for example, are now raised along
the Pacific Coast, and many have escaped from the pens and have been breeding in
some West Coast rivers, where they compete with native species and spread diseases.
c. Over Time. The transplantation of species by humans has occurred throughout
history, to the point where most people are unable to distinguish between the native and
exotic species living in their lands. European colonists brought hundreds of weeds and
plants to the Americas, and now most of the common field, lawn, and roadside plant
species in eastern North America are exotics. For example, almost one-third of the plants
in Massachusetts are alien or introduced—about 725 species, of which 66 have been
specifically identified as invasive or likely to become so. In Europe, there are about 11,000
alien species, 15% of which harm biodiversity.
In North America, two invasive animals of particular concern are the Burmese python and
the wild boar. Burmese pythons have been released into the wild by pet owners who no
longer like them once they become large. There are now breeding populations of these
snakes in the Florida Everglades, where they eat the native wildlife and are dangerous to
humans. Wild boar were introduced by people who wanted to hunt and eat them. Today
there are an estimated 4 million feral boar in the United States. They are dangerous and
tear up soil, rooting up plants. One of the most destructive exotics is the house cat:
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Studies in the 1990s showed that the millions of domestic and feral cats in the United
States kill an estimated 1 billion small mammals (chipmunks, deer mice, and ground
squirrels, as well as rats) and hundreds of millions of birds annually. One report calculates
the annual cost of invasive other places, too. For example, the North American gray
squirrel is invasive in Europe, where it outcompetes the native red squirrels and may be
infecting them with a fatal virus. The gray squirrel is one of the 100 most invasive species
worldwide.
d. Invasive Species and Trophic Levels. Plants provide food for herbivores that in
turn provide food for carnivores. Non-native plants may be difficult for herbivores to eat
and thus may keep energy and materials from passing up the food chain, even if a species
has been in a new ecosystem for a long time. For example, the Norway maple was
introduced to North America in 1756, but in spite of being in the United States for more
than 250 years, these maples provide much less food for herbivores (like caterpillars) and
their predators (like songbirds) than native trees do.
3. POLLUTION. Another factor that decreases biodiversity is pollution, which can
directly kill many kinds of plants and animals, seriously reducing their populations. For
example, nutrients (such as phosphorus and nitrogen) that travel down the Mississippi
River from the agricultural heartland of the United States have created a fluctuating “dead
zone” in the Gulf of Mexico, an area of more than 5,052 square miles (in 2014) where
oxygen completely disappears from depths below 20 meters every summer. Shrimp, fish,
crabs, and other commercially valuable sea life are either killed or forced to migrate away
from this huge area along the Mississippi and Louisiana coastline.
Pollution destroys or alters habitats, with consequences just as severe as those caused
by deliberate conversions. Every oil spill kills seabirds and often sea mammals, sometimes by the thousands. Some pollutants, such as the pesticide DDT, can travel up food
chains and become more concentrated in higher consumers. Acid deposition and air
pollution kill forest trees; sediments and large amounts of nutrients kill species in lakes,
rivers, and bays; and global climate change, brought on by greenhouse gas emissions, is
already affecting many species.
Pollution can spread disease. Human wastes can spread pathogenic microorganisms to
wild species, a threat called pathogen pollution. For example, the manatee (an
endangered aquatic mammal) has been infected by human papillomavirus,
cryptosporidium, and microsporidium, with fatal outcomes. Pollution can also disrupt
hormones and other body functions. Fish exposed to polluted river water may develop
tumors or deformed organs. The recent and rapid rise in the incidence of these deformities
has been traced to habitats that have been altered by human use, specifically run-off,
industry, and sewage in populated areas.
4. POPULATION. Human population growth puts pressure on wild species through
several mechanisms—through direct use of wild species, through conversion of habitat
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into agriculture or other use, through pollution, and through having to compete for
resources with growing human populations. Overconsumption is tied to overpopulation
and to the concept of overexploitation. Even if each person using a resource used a
modest amount, large numbers of people might still use too much, leading to a total
overconsumption. Thus, overpopulation is a problem even if individuals use few
resources. However, a small group of people can also overuse resources. Indirectly,
overconsumption can drive pollution, conversion of habitat, and other effects that harm
wildlife. In a world in which some individuals own literally billions of times the money and
resources that others own, people with the most consumptive lifestyles have a
disproportionate effect on the environment. Differences in level of consumption, therefore
one’s lifestyle affects our biodiversity where resources are obtained.
5. OVEREXPLOITATION. The overharvest of a particular species is known as
overexploitation. Removing whales, fish, or trees faster than they can reproduce will lead
to their ultimate extinction. The extinction of the passenger pigeon is one compel- ling
example. In addition, overuse of individual species harms ecosystems. Overexploitation
is estimated to have caused 23% of recent extinctions (past 500 years) and is often driven
by a combination of greed, ignorance, and desperation.
Poor resource management often leads to a loss of biodiversity. Forests and woodlands
are overcut for firewood, grasslands are overgrazed, game species are overhunted,
fisheries are overexploited, and croplands are overcultivated. These practices set into
motion a cycle of erosion and desertification, with effects far beyond the exploited area.
Trade in Wild Products. One prominent form of over-use is the trafficking in wildlife and
in products derived from wild species. Much of this “trade” is illegal. Worldwide, the U.N.
Environmental Program estimates that it generates $7 to $23 billion a year, making it
among the most lucrative illicit sources of income, after narcotics, counterfeiting, and
human trafficking. This illegal activity flourishes because some consumers are willing to
pay exorbitant prices for furniture made from tropical hardwoods (like teak), exotic pets,
furs from wild animals, traditional medicines from animal parts, and innumerable other
“luxuries,” including polar-bear rugs, ivory-handled knives, and reptile-skin handbags. For
example, a panda-skin rug can sell for up to $25,000 in the United States.
The plight of various species of rhinoceros demonstrates the harm caused by the illegal
trade in wildlife products. In 2011, the West African rhino was declared extinct. In October
2011, the Javan rhino was declared extinct in mainland Asia, surviving in only a small
population in Indonesia. Rhino species are all very rare because of the high value placed
on their horns; poachers kill rhinos to remove their horns, which are prized in Asian
medicine and used for ornamental knife handles in the Middle East. Even preemptive
removal of the rhinos’ horns by wildlife managers does not protect the animals, because
poachers kill them for the remaining bases of their horns. In addition, the dehorned
animals do not survive well in the wild. Wildlife officials post guards around the rarest
animals or move them to safer locations. One South African Group, the Rhino Rescue
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Project, attempts to make poaching less appealing by devaluing horns. Veterinarians drill
small holes into the horns of sedated rhinos and put in a substance toxic to humans that
will make the horn impossible to use in alternative medicine. Microchips are added and
sometimes dye. Another solution is aggressive advertising against wild animal parts. An
advertising campaign in Vietnam saw demand for rhino horn drop a third between 2013
and 2014. Protecting rhinos, like many other creatures, will take coordinated approaches.
In 2010, a report by two United Nations environmental bodies warned that unless radical
and creative action is taken to conserve the earth’s biodiversity, many local and regional
ecosystems that help to support human lives and livelihoods are at risk of collapsing.
Case Study 6: Costa Rica
Tropical forests once completely covered Central America’s Costa Rica, which is smaller in
area than the U.S. state of West Virginia and about one-tenth the size of France. Between 1963
and 1983, politically powerful ranching families cleared much of the country’s forests to graze
cattle.
Despite such widespread forest loss, tiny Costa Rica is a superpower of biodiversity, with an
estimated 500,000 plant and animal species. A single park in Costa Rica is home to more bird
species than are found in all of North America. This oasis of biodiversity is also home to an
amazing variety of other exotic wildlife, including, monkeys, jaguars, snakes, spiders, and frogs.
This biodiversity results mostly from two factors: first, the country’s tropical geographic location,
lying between two oceans and having both coastal and mountainous regions that provide a
variety of microclimates and habitats for wildlife; and second, the government’s strong
conservation efforts.
In the mid-1970s, Costa Rica established a system of nature reserves and national parks that,
by 2012, included more than 25% of its land—6% of it reserved for indigenous peoples. Costa
Rica has increased its beneficial environmental impact by devoting a larger proportion of its land
than any other country has to biodiversity conservation, in keeping with the biodiversity principle
of sustainability.
To reduce deforestation, or the widespread removal of forests, the government has eliminated
subsidies for converting forestland to rangeland. Instead, it pays landowners to maintain or
restore tree cover. The strategy has worked: Costa Rica has gone from having one of the world’s
highest deforestation rates to having one of the lowest. Ecologists warn that human population
growth, economic development, and poverty are exerting increasing pressure on the earth’s
ecosystems and on the ecosystem services they provide that help to sustain biodiversity.
Identifying and Protecting Biodiversity in Costa Rica
For several decades, Costa Rica has been using government and private research agencies to
identify the plants and animals that make it one of the world’s most biologically diverse countries.
The government has consolidated the country’s parks and reserves into several large
conservation areas, or megareserves, designed with the goal of sustaining about 80% of the
country’s biodiversity.
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Each reserve contains a protected inner core surrounded by two buffer zones that local and
indigenous people can use for sustainable logging, crop farming, cattle grazing, hunting, fishing,
and ecotourism. Instead of shut ting people out of the protected areas, this approach enlists
local people as partners in protecting a reserve from unsustainable uses such as illegal logging
and poaching. It is an application of the biodiversity and win-win principles of sustainability.
In addition to its ecological benefits, this strategy has paid off financially. Today, Costa Rica’s
largest source of income is its $1-billion-a-year tourism industry, almost two-thirds of which
involves ecotourism.
Ecological Restoration of a Tropical Dry Forest in Costa Rica
Costa Rica is the site of one of the world’s largest ecological restoration projects. In the lowlands
of its Guanacaste National Park, a tropical dry forest was burned, degraded, and fragmented
for large-scale conversion to cattle ranches and farms. Now it is being restored and reconnected
to a rain forest on nearby mountain slopes. The goal is to eliminate damaging nonnative grasses
and reestablish a tropical dry-forest ecosystem during the next 100–300 years.
Daniel Janzen, professor of conservation biology at the University of Pennsylvania and a leader
in the field of restoration ecology, used his own MacArthur Foundation grant money to purchase
the Guanacaste forestland for designation as a national park. He also raised more than $10
million for restoring the park.
Janzen recognizes that ecological restoration and protection of the park will fail unless the
people in the surrounding area believe they will benefit from such efforts. His vision is to see
that the nearly 40,000 people who live near the park play an essential role in the restoration of
the forest, a concept he calls biocultural restoration.
In the park, local farmers are paid to remove nonnative species and to plant tree seeds and
seedlings started in Janzen’s lab. Local grade school, high school, and university students and
citizens’ groups study the park’s ecology during field trips. The park’s location near the Pan
American Highway makes it an ideal area for ecotourism, which stimulates the local economy.
This project also serves as a training ground in tropical forest restoration for scientists from all
over the world. Research scientists working on the project give guest classroom lectures and
lead field trips. Janzen believes that education, awareness, and involvement—not guards and
fences—are the best ways to protect largely intact ecosystems from unsustainable use so they
can be restored.
Activity:
1. Describe factors affecting species richness and explain how and why the species
richness of a rice field might differ from that of a coral reef.
2. What are the four main causes of species endangerment and extinction? Which
would you consider most important?
3. What are invasive species? How might their presence particularly affect biodiversity
hotspots?
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Lesson 6: Climate Change/Global Warming
What is Climate Change?
Climate change is a long-term change in the average weather patterns that have come to
define Earth’s local, regional and global climates.
Scientists use observations from the ground, air and space, along with theoretical models,
to monitor and study past, present and future climate change. Climate data records
provide evidence of climate change key indicators, such as global land and ocean
temperature increases; rising sea levels; ice loss at Earth’s poles and in mountain glaciers;
frequency and severity changes in extreme weather such as hurricanes, heatwaves,
wildfires, droughts, floods and precipitation; and cloud and vegetation cover changes, to
name but a few.
The issue of Climate Change is a collective effect of Scientific, Economic and Political
issues. Previous topics discussed in this module either contribute to or are the causes of
these global climate change.
Global climate change has been described as the ‘mother’ of all problems. This rhetoric
suggests that devastating events will unfold as humanity marches blindly forward
demanding more and more materials such as autos, jet travel, and air-conditioned homes.
Once having crossed over the precipice, there will be no returning to our previous way of
life. The Earth’s atmosphere will have been irreversibly violated and humans must forever
reap the consequences of their extravagant and carefree lifestyle.
Whether or not this alarmist view is correct is open to debate. But in another sense, we
can agree that as an intellectual exercise, climate change appears to be the ‘mother’ of
all problems because of its complexity. Climate change brings together the disciplines of
botany, climatology, biology, atmospheric and oceanic chemistry, glaciology, systems
modeling, cloud physics, statistics, economics, and political science. It seems impossible
for any one person to achieve proficiency in all these areas.
Changes observed in Earth’s climate since the early 20th century are primarily driven by
human activities, particularly fossil fuel burning, which increases heat-trapping
greenhouse gas levels in Earth’s atmosphere, raising Earth’s average surface
temperature. These human-produced temperature increases are commonly referred to
as global warming. Natural processes can also contribute to climate change, including
internal variability (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific
Decadal Oscillation) and external forces (e.g., volcanic activity, changes in the Sun’s
energy output, variations in Earth’s orbit).
Climate is one of the primary factors that determines the distribution of wild plants and
animals around the world. There is evidence from the past of how species respond when
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the climate changes. About 18,000 years ago at the peak of the last glacial period, the
vegetation over most of the northern half of the United States was primarily boreal forest
and tundra. Today, those vegetation types and their associated animal species are found
in central and northern Canada. As the world warmed following glaciation, species moved
to higher latitudes, or upslope in mountainous areas, following a climate to which they
adapted.
While we have a sense of how species will respond, there are some major differences
between the former and current climate changes that threaten many species. The current
rate of change is many times faster than what occurred coming out of the ice age. That
warming took roughly 8,000 years, while we will likely see the same magnitude of global
temperature increase in less than 300 years this time. Many species with limited ability to
move, such as plants and nonflying invertebrates, will simply not be able to keep up as
the climate to which they are adapted moves on.
In addition, the natural landscape is now more fragmented by human development such
as cropland, highways, and cities. This development forms a barrier to the movement of
many species and will inhibit their ability to respond to climate change.
The changing climate also is affecting the timing of annual events in the life cycle of
species. Studies have documented recent shifts in the timing of migration, insect
emergence, flowering and leaf out, all driven by the earlier arrival of spring. Not all species
are responding in the same way, and this can lead to the uncoupling of ecological
relationships among species. For example, insect emergence is occurring up to three
weeks earlier in the Arctic, while migratory songbirds are not leaving their wintering
grounds earlier because they rely on day length, not temperature, as a cue to begin
migration. Thus, they may be arriving in the Arctic as a key food resource for nesting is
declining, resulting in less successful reproduction.
Scientists predict that one-fourth of Earth’s species will be headed for extinction by 2050
if the warming trend continues at its current rate.
Different issues identified by United Nations Environmental Protection (UNEP) are likely
to be the repercussion of Climate Change
Climate change is a significant threat to our existence as human. At this rate of our
activities, climate change is inevitable. We need to be able to prepare ourselves for the
worst outcome while at the same time work on mitigating it. Meanwhile, around the globe,
human life, to greater and lesser extents, depends on materials and energy sources
extracted from the planet, which are then transformed by technology into the goods and
services which are necessary to our daily way of life. This treatment of the resources
provided by our planet as if it is renewable and can easily be replenished jeopardizes the
biosphere, while at the same time climate change will jeopardize the way we consume
resources in a variety of interlocking ways.
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In June of 1991, after 600 years of slumber, Mount Pinatubo in the Philippines exploded.
A huge amount of volcanic material blasted out of the mountain, sending a cloud of air
pollutants and ash to a height of 35 kilometers (22 miles). Avalanches of hot gases and
ash roared down the sides of the mountain, filling valleys with volcanic deposits. It was
the second-largest volcanic eruption of the 20th century.
The eruption of Mount Pinatubo killed hundreds of people, destroyed homes and
farmland, and caused hundreds of millions of dollars in damage. At the same time, it
enabled scientists to test whether they understood the global climate well enough to
estimate how the eruption would affect temperatures on the earth.
By the late 1980s, most of the world’s climate scientists had become concerned that
human actions, especially fossil fuel use, were enhancing the world’s natural greenhouse
effect and contributing to a rise in the average temperature of the atmosphere. Some
stated publicly that such global warming was likely to occur and could have disastrous
ecological and economic effects. Their concerns were based in part on results from
computer models of the global climate.
Although their complex global climate models mimicked past and present climates well,
Mount Pinatubo provided scientists with an opportunity to perform a more rigorous test of
such models. Soon after the volcano erupted, James Hansen, a U.S. National
Aeronautics and Space Administration (NASA) scientist, estimated that the Pinatubo
explosion would probably cool the average temperature of the earth by 0.5 C° (1 F°) over
a 19-month period. The earth would then begin to warm, Hansen said, and by 1995 would
return to the temperatures observed before the explosion. His projections turned out to
be correct.
To make his forecasts, Hansen added the estimated amount of sulfur dioxide released by
the volcano’s eruption to a global climate model and then used the model to forecast how
the earth’s temperature would change. His model passed the test with flying colors. Its
success helped convince most scientists and policy makers that climate model
projections—including the impact of human actions—should be taken seriously.
Hansen’s model and nineteen other climate models indicate that global temperatures are
likely to rise several degrees during this century—mostly because of human actions—and
affect the earth’s global and regional climates, economies, and human ways of life. To
many scientists and a growing number of business executives, global climate change
(a broad term referring to changes in any aspects of the earth’s climate, including
temperature, precipitation, and storm activity) represents the biggest challenge that
humanity faces during this century.
Climate scientists warn that the concern is not just about how much the temperature
changes but also about how rapidly it occurs. Most past changes in the temperature of
the lower atmosphere took place over thousands to a hundred thousand years. The next
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problem we face is a rapid increase in the average temperature of the lower atmosphere
during this century. In other words, according to the International Panel for Climate
Change (IPCC) and other climate scientists, the earth’s atmosphere is running a fever
that is rising fast, mostly because of human activities.
Such rapid change could drastically affect life on earth. Humans have built a civilization
adapted to the generally favorable climate we have had for the past 10,000 years. Climate
models indicate that within only a few decades, we will have to deal with a rapidly
changing climate.
A 2003 U.S. National Academy of Sciences report laid out a nightmarish worst-case
scenario in which hu- man activities, alone or in combination with natural factors, trigger
new and abrupt changes. At that point, the global climate system would reach a tipping
point after which it would be too late to reverse catastrophic change for tens of thousands
of years.
The report describes ecosystems suddenly collapsing, low-lying cities being flooded,
forests being consumed in vast fires, grasslands drying out and turning into dust bowls,
premature extinction of up to half of the world’s species, prolonged heat waves and
droughts, more intense coastal storms and hurricanes, and tropical infectious diseases
spreading rapidly beyond their cur- rent ranges. Climate change can also threaten peace
and security as changing patterns of rainfall increase competition for water and food
resources, cause destabilizing migrations of tens of millions of people, and lead to
economic and social disruption.
Activity:
1. Cite one specific sector you think will eventually be affected/impacted by climate
change. It can be a positive or a negative impact.
2. How will it be affected? Discuss the factors that will lead to it.
Lesson 7: Ozone Depletion
Look around you. What do you see? In our own houses, we are protected by our
roof. In our planet, the Earth, we are protected by our atmosphere which contains the
ozone. The Ozone is Earth’s only defense against harmful UVR. Studies indicate that the
ozone is thinning throughout the globe due chemicals reaching the stratosphere. In the
last decade, there has been an increase in skin cancer and cataracts all related to
increase UV-B exposure. There are human activities which aggravate the thinning of the
ozone and most are not aware of it. The effects of the thinning ozone are taking its toll in
the way we humans and other creatures live. This module will deal with the layers of the
earth’s atmosphere, where the ozone is located. The functions of the ozone will be
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discussed and how it is being destroyed by human activities. Activities that would simulate
the formation and destruction of ozone will be provided for better understanding of the
processes.
A. THE OZONE LAYER
What roles does ozone play in the atmosphere and how are humans affected?
The ozone molecules in the upper atmosphere (stratosphere) and the lower atmosphere
(troposphere) are chemically identical, because they all consist of three oxygen atoms
and have the chemical formula O3. However, they have very different roles in the
atmosphere and very different effects on humans and other living beings. Stratospheric
ozone (sometimes referred to as "good ozone") plays a beneficial role by absorbing most
of the biologically damaging ultraviolet sunlight (called UV-B), allowing only a small
amount to reach the Earth's surface. The absorption of ultraviolet radiation by ozone
creates a source of heat, which actually forms the stratosphere itself (a region in which
the temperature rises as one goes to higher altitudes). Ozone thus plays a key role in the
temperature structure of the Earth's atmosphere. Without the filtering action of the ozone
layer, more of the Sun's UV-B radiation would penetrate the atmosphere and would reach
the Earth's surface. Many experimental studies of plants and animals and clinical studies
of humans have shown the harmful effects of excessive exposure to UV-B radiation.
At the Earth's surface, ozone comes into direct contact with life-forms and displays its
destructive side (hence, it is often called "bad ozone"). Because ozone reacts strongly
with other molecules, high levels of ozone are toxic to living systems. Several studies
have documented the harmful effects of ozone on crop production, forest growth, and
human health. The substantial negative effects of surface-level tropospheric ozone from
this direct toxicity contrast with the benefits of the additional filtering of UV-B radiation that
it provides.
Without the ozone layer, the Earth's surface would be sterilized by UV radiation. The
breakdown of the ozone layer increases skin cancer and cataracts in humans, impairs
immune systems of all animals (including humans), and interferes with phytoplankton
productivity in the oceans.
Human Impacts on the Ozone Layer
What human activities affect upper-atmospheric ozone? Humans have impacted the
ozone layer: Chlorofluorocarbons (CFCs) used for refrigeration, cleaning solvents, and
aerosol sprays since the 1950s help destroy ozone. Ozone became strongly depleted
over the Earth's Polar Regions in the later part of the 20th century.
The scientific evidence, accumulated over more than two decades of study by the
international research community, has shown that human-produced chemicals are
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responsible for the observed depletions of the ozone layer. The ozone-depleting
compounds contain various combinations of the chemical elements chlorine, fluorine,
bromine, carbon, and hydrogen and are often described by the general term halocarbons.
The compounds that contain only chlorine, fluorine, and carbon are called
chlorofluorocarbons, usually abbreviated as CFCs. CFCs, carbon tetrachloride, and
methyl chloroform are important human-produced ozone-depleting gases that have been
used in many applications including refrigeration, air conditioning, foam blowing, cleaning
of electronics components, and as solvents. Another important group of human-produced
halocarbons is the halons, which contain carbon, bromine, fluorine, and (in some cases)
chlorine and have been mainly used as fire extinguishants.
Perform Activity Whole Body Ozone Chemistry Part 3 (Refer to Appendix A) and let pupils
answer the guide questions.
EFFECTS OF OZONE DEPLETION: Losing the ozone layer
Even minor problems of ozone depletion can have major effects. Every time even a
small amount of the ozone layer is lost, more ultraviolet light from the sun can reach the
Earth. Here are some of the effects of the ozone layer depletion.
1. Effects on Human and Animal Health
Every time 1% of the ozone layer is depleted, 2% more UV-B is able to reach the surface
of the planet. UV-B increase is one of the most harmful consequences of ozone depletion
because it can cause skin cancer.
The increased cancer levels caused by exposure to this ultraviolet light could be
enormous. The EPA estimates that 60 million Americans born by the year 2075 will get
skin cancer because of ozone depletion. About one million of these people will die.
In addition to cancer, some research shows that a decreased ozone layer will increase
rates of malaria and other infectious diseases. According to the EPA, 17 million more
cases of cataracts can also be expected.
The increases in UV-B radiation associated with ozone depletion are likely to lead to
increases in the incidence and/or severity of a variety of short-term and long-term health
effects, if current exposure practices are not modified by changes in behavior.
2. Effects on Terrestrial Ecosystems
The environment will also be negatively affected by ozone depletion. The life cycles of
plants will change, disrupting the food chain. Effects on animals will also be severe, and
are very difficult to foresee.
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3. Effects on Aquatic Ecosystems
Oceans will be hit hard as well. The most basic microscopic organisms such as plankton
may not be able to survive. If that happened, it would mean that all of the other animals
that are above plankton in the food chain would also die out. Other ecosystems such as
forests and deserts will also be harmed.
Effects on Biogeochemical Cycles
Effects of increased UV-B on emissions of carbon dioxide and carbon monoxide (CO)
and on mineral nutrient cycling in the terrestrial biosphere have been confirmed by recent
studies of a range of species and ecosystems. The effects, both in magnitude and
direction, of UV-B on trace gas emissions and mineral nutrient cycling are species-specific
and operate on a number of processes. These processes include changes in the chemical
composition in living plant tissue, photodegradation (breakdown by light) of dead plant
matter, including litter, release of carbon monoxide from vegetation previously charred by
fire, changes in the communities of microbial decomposers and effects on nitrogen-fixing
micro-organisms and plants. Long-term experiments are in place to examine UV-B effects
on carbon capture and storage in biomass within natural terrestrial ecosystems.
4. Effects on Air Quality
Increased UV-B will increase the chemical activity in the lower atmosphere (the
troposphere). Tropospheric ozone levels are sensitive to local concentrations of nitrogen
oxides (NOx) and hydrocarbons. Model studies suggest that additional UV-B radiation
reduces tropospheric ozone in clean environments (low NO x), and increases tropospheric
ozone in polluted areas (high NOx).
What Humans Can do to preserve the Ozone?
Ways to Protect the Ozone Layer:
1. Minimize high altitude aircraft flights (oxygen reduction and water vapor
deposition)
2. Minimize rocket flights (water vapor deposition)
3. Encourage growth of plants that produce oxygen, discourage deforestation
4. Decrease / control releases of high temperature steam / moisture to the
atmosphere
5. Eliminate production and release of known ozone depleting chemicals (such as
CFCs and
HCFCs) where remotely possible. Subsidize production of safer
alternatives where possible.
6. Establish controls to assure that new compounds to be used in high volume, are
surveyed for effect on ozone.
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Note that there is only one way for significant amounts of CFC emissions to leave our
atmosphere permanently. And that is by them entering the ozone layer, and being
destroyed by the abundant UV-B and UV-C radiation there. The "climb" takes a long time,
and we have been releasing these gases since the early 1900s in large quantities and
they are much heavier in the air.
Lesson 8: Sustainability
Sustainability is the ability of the earth’s various natural systems and human cultural
systems and economies to survive and adapt to changing environmental conditions
indefinitely.
A critical component for sustainability is the natural capital—the natural resources and
natural services provided by nature that keep us and other species alive and support
our economies. Natural resources are materials and energy in nature that are essential
or useful to humans. These resources are often classified as renewable (such as air,
water, soil, plants, and wind) or nonrenewable (such as copper, oil, and coal). Natural
services are functions of nature, such as purification of air and water, which support life
and human economies.
A critical natural service is nutrient cycling, the circulation of chemicals necessary for life
from the environment (mostly soil and water) through organisms and back to the
environment. Without this service, life as we know it will not exist.
Natural capital is supported by solar capital: energy from the sun that warms the planet
and supports photosynthesis—a complex chemical process that plants use to provide
food for themselves and for us and other animals. This direct input of solar energy also
produces indirect forms of renewable solar energy such as wind, flowing water, and
biofuels made from plants and plant residues. Thus, our lives and economies depend on
energy from the sun (solar capital) and natural resources and natural services (natural
capital) provided by the earth
A second component of sustainability is to recognize that many human activities can
degrade natural capital by using normally renewable resources faster than nature can
renew them. For example, in parts of the world we are clearing mature forests much
faster than nature can replenish them. We are also harvesting many species of ocean
like fish, faster than they can replenish themselves.
This leads us to the third component of sustainability: the scientific search for solutions
to these and other environmental problems. Implementing such solutions involves using
our economic and political systems. For example, scientific solutions might be to stop
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clear-cutting biologically diverse, mature forests, and to harvest fish species no faster
than they can replenish themselves. Implementing such solutions would probably
require government laws and regulations.
The search for solutions often involves conflicts. Thus, another component of the shift
toward sustainability involves trying to resolve these conflicts by making trade-offs, or
compromises. To provide wood and paper, for example, paper companies can plant tree
farms in areas that have already been cleared or degraded, in exchange for preserving
mature forests.
Any shift toward environmental sustainability should be based on scientific concepts and
results that are widely accepted by experts in a particular field. In making such a shift,
individuals matter. Individuals vary widely in their abilities, but everyone can contribute
to finding and implementing solutions to environmental problems. Some people are
good at thinking of new ideas and inventing innovative technological solutions. Others
are good at putting political pressure on government officials and business leaders,
acting either alone or in groups to implement those solutions. Still others know how to
be wise consumers who vote with their pocketbooks to help bring about environmental
and social change. Regardless, every individual is as important as the next in bringing
about a shift toward sustainability.
Three Scientific Principles of Sustainability
How has the incredible variety of life on the earth been sustained for at least 3.8 billion
years in the face of catastrophic changes in environmental conditions? Such changes
included gigantic meteorites impacting the earth, ice ages lasting for hundreds of millions
of years, and long warming periods during which melting ice raised sea levels by hundreds
of feet. The latest version of our species has been around for only about 200,000 years—
less than the blink of an eye, relative to the 3.8 billion years that life has existed on the
planet. Yet, there is mounting scientific evidence that, as we have expanded into and
dominated almost all of the earth’s ecosystems during that short time, and especially
since 1900, we have seriously degraded these natural systems that support all species,
including our own, and our economies. Our science-based research leads us to believe
that three major natural factors have played the key roles in the long-term sustainability
of life on this planet. We use these three scientific principles of sustainability, or
lessons from nature, to suggest how we might move toward a more sustainable future.
• Dependence on solar energy: The sun’s input of energy, called solar energy, warms
the planet and provides energy that plants use to produce nutrients, the chemicals
necessary for their own life processes and for those of most other animals, including
humans. The sun also powers indirect forms of solar energy such as wind and flowing
water, which we use to produce electricity.
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• Biodiversity: The variety of genes, organisms, species, and ecosystems in which
organisms exist and interact are referred to as biodiversity (short for biological diversity).
The interactions among species, especially the feeding relationships, provide vital
ecosystem services and keep any population from growing too large. Biodiversity also
provides countless ways for life to adapt to changing environmental conditions, even
catastrophic changes that wipe out large numbers of species.
• Chemical cycling: The circulation of chemicals necessary for life from the environment
(mostly from soil and water) through organisms and back to the environment is called
chemical cycling, or nutrient cycling. The earth receives a continuous supply of energy
from the sun, but it receives no new supplies of life-supporting chemicals. Thus through
their complex interactions with their living and nonliving environment, organisms must
continually recycle the chemicals they need in order to survive. This means that there is
little waste in nature, other than in the human world, because the wastes and decayed
bodies of any organism become nutrients or raw materials for other organisms. In nature,
waste = useful resources
Ecology and environmental science reveal that interdependence, not independence, is
what sustains life and allows it to adapt to a continually changing set of environmental
conditions. Many environmental scientists argue that understanding this interdependence
is the key to learning how to live more sustainably.
Miller Spoolman 15th Ed
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Sustainability Has Certain Key Components
Sustainability, the central integrating theme of this book, has several critical components
that we use as subthemes. One such component is natural capital—the natural
resources and ecosystem services that keep us and other species alive and support
human economies. Natural resources are materials and energy in nature that are
essential or useful to humans. They are often classified as inexhaustible resources (such
as energy from the sun and wind), renewable r another component of sustainability. For
example, the timber company might be persuaded to plant and harvest trees in an area
that it had already cleared or degraded, instead of clearing the undisturbed forest. In
return, the government might give the company a subsidy, or financial support, to meet
some of the costs for planting the trees. In making a shift toward sustainability, the daily
actions of each and every individual are important. In other words, individuals matter.
History shows that almost all of the significant changes in human systems that have
improved environmental quality have come from the bottom up, through the collective
actions of individuals and from individuals inventing more sustainable ways of doing
things. Ecosystem services are processes provided by healthy ecosystems that support
life and human economies at no monetary cost to us. Examples include purification of air
and water, renewal of topsoil, nutrient cycling, pollination, and pest control.
One essential ecosystem service is chemical, or nutrient, cycling—the basis for one of
the three scientific principles of sustainability. Chemical cycling helps to turn wastes into
resources. An important component of nutrient cycling is topsoil—a vital natural resource
that provides us and most other land-dwelling species with food. Without nutrient cycling
in topsoil, life as we know it could not exist on the earth’s land.
Natural capital is also supported by energy from the sun—the focus of another of the
scientific principles of sustainability. Thus, our lives and economies depend on energy
from the sun, and on natural resources and ecosystem services (natural capital) provided
by the earth.
A second component of sustainability—and another subtheme of this text—is to recognize
that many human activities can degrade natural capital by using normally renewable
resources such as trees and topsoil faster than nature can restore them and by
overloading the earth’s normally renewable air and water systems with pollution and
wastes. For example, in some parts of the world, we are replacing diverse and naturally
sustainable forests (Figure1.4) with crop plantations that can be sustained only with large
inputs of water, fertilizer, and pesticides. We are also adding harmful chemicals and
wastes to some rivers, lakes, and oceans faster than these bodies of water can cleanse
themselves through natural processes. In addition, we are disrupting the nutrient cycles
that support life because many of the plastics and other synthetic materials that we have
created cannot be broken down and used as nutrients by other organisms.
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This leads us to a third component of sustainability: solutions. While environmental
scientists search for scientific solutions to problems such as the degradation of forests
and other forms of natural capital, social scientists are looking for economic and political
solutions. For example, a scientific solution to the problems of depletion of forests is to
stop burning or cutting down biologically diverse, mature forests. A scientific solution to
the problem of pollution of rivers is to prevent the excessive dumping of harmful chemicals
and wastes into streams and to allow them to recover naturally. However, to implement
such solutions, governments often have to enact and enforce environmental laws and
regulations. The search for solutions often involves conflicts. For example, when a
scientist argues for protecting a long undisturbed forest to help preserve its important
biodiversity, the timber company that had planned to harvest the trees in that forest might
protest. Dealing with such conflicts often involves making trade-offs, or compromises—
another component of sustainability. For example, the timber company might be
persuaded to plant and harvest trees in an area that it had already cleared or degraded,
instead of clearing the undisturbed forest. In return, the government might give the
company a subsidy, or financial support, to meet some of the costs for planting the trees.
In making a shift toward sustainability, the daily actions of each and every individual are
important.
Activity:
1. Why is human population control an important part of global sustainability?
2. What is food insecurity? How does food insecurity affect the environment?
Resources:
https://earthjournalism.net/stories/philippine-forests-are-rapidly-disappearing
https://www.nationalgeographic.com/environment/global-warming/deforestation
https://www.who.int/health-topics/air-pollution#tab=tab_1
https://essc.org.ph/content/lview/579/1/
https://www.urban-hub.com/sustainability/less-bad-more-good-pioneering-a-circular-economywith-cradle-to-cradle/
https://recyclenation.com/2015/05/history-of-three-r-s/
Cunningham, W. C., & Cunningham, M. (2020). Principles of Environmental Science: inquiry and
applications (9th ed.). 2 Penn PLaza, New York: Mcgraw-Hill Education.
Berg, L. R., Hager, M., & Hassenzahl, D. M. (2014). Visualizing Environmental Science (4th ed.).
River Street, Hoboken,, New Jersey: John Wiley.
Enger, E. D., & Smith, B. F. (2019). Environmental Science: A Study of Interrelationships (14th
ed.). New York, NY: McGraw-Hill Education.
Hadjichambis, A. C., Reis, P., & Paraskeva-Hadjichambi, D. (2020). Conceptualizing
Environmental citizenship for 21st century education (Vol. 4). Cham, Switzerland,
Tennessee: Springer Open.
Marselle, M. R., Stadler, J., Korn, H., & Irvine, K. N. (2019). Biodiversity and Health in the Face of
Climate Change. Springer International Publishing.
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Module 8:
PHILIPPINE AGENDA
Time Frame: 1 Week (Week 18)
Overview:
Philippine Agenda 21
The younger generation is our future – someday they will be the decision-makers,
educators, and possibly even policy makers of our world and country. What we are
teaching them today is going to affect their lifestyle choices in the coming years, so we
need to focus on preparing them for the changing world and environment. Teaching our
children about sustainability will give them the opportunity to take responsibility for their
actions, plan for the future, and maintain a healthier planet.
Objectives:
1. Investigate how to enhance and maintain biophysical systems and improve
biodiversity.
2. Investigate the aspects of sustainability in different contexts.
3. Examine the values and behaviors that will contribute to a sustainable future.
4. Plan, implement, and evaluate personal action for a sustainable future.
5. Evaluate social, economic, and technological measures that could be taken to
sustain natural resources and improve biodiversity now and for the future.
6. Analyze the impact of strategies and initiatives for a sustainable future.
7. Analyze the values of different groups of people, how these values are expressed
in various practices, and the present and future consequences for sustainability.
8. Analyze actions necessary for sustainability and plan, implement, and critically
evaluate personal action for a sustainable future.
A. What is Agenda 21
Agenda 21 is a comprehensive plan of action to be taken globally, nationally and locally
by organizations of the United Nations System, Governments, and Major Groups in every
area in which human impacts on the environment
Agenda 21, the Rio Declaration on Environment and Development, and
the Statement of principles for the Sustainable Management of Forests were
adopted by more than 178 Governments at the United Nations Conference on
Environment and Development (UNCED) held in Rio de Janerio, Brazil, 3 to 14
June 1992.
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The full implementation of Agenda 21, the Programme for Further Implementation
of Agenda 21 and the Commitments to the Rio principles, were strongly reaffirmed
at the World Summit on Sustainable Development (WSSD) held in Johannesburg,
South Africa from 26 August to 4 September 2002.
Philippine Agenda 21 is the nation’s blueprint for sustainable development. In
concreting the vision, it describes a path for individuals, families, households and
communities; an action plan for each ecosystem (coastal/marine, freshwater,
upland, lowland, and urban); and across ecosystems in consideration of the
interaction of the various lifescapes and landscapes found therein. The path is
grounded on respect and active advocacy for the empowerment of the various
social groupings of society to manage the economy, critical resources, society and
culture, politics and governance and in the arena of foreign relations.
PA 21 was adopted on 26 September 1996, with the issuance of Memorandum
Order No. 399 by then President Fidel V. Ramos which identified the roles of the
Philippine Council for Sustainable Development (PCSD) and each sector in the
operationalization of PA 21. The action agenda is based on the imperatives of
the current national situation and emerging landscape for sustainable
development.
B. PA21 Key Concepts
1. Integration.
Sustainable development in the Philippines permeate the rhetoric of many development
players providing considerable scope for integration. In this context, PA 21 does not
duplicate existing and on-going initiatives related to sustainable development; rather, it
builds on these efforts. A critical part of the PA 21 process involved a scanning of the
various initiatives that have enriched and sought to operationalize sustainable
development. At the same time, it seeks to develop an emerging and growing identity that
is distinct from these initiatives, an identity that will bridge PA 21 as an interstice towards
sustainable development as the overarching framework. In the process of its formulation,
therefore, an attempt was made to synergize and contextualize the diversity of existing
initiatives.
It effectively is an accumulation of conceptual and operational breakthroughs generated
by the Philippine Strategy for Sustainable Development, Social Reform Agenda , and the
Human and Ecological Security, among others. Sustainable development is also a
product of the process itself, of engaging various stakeholders and simultaneously
working in global, national and local arenas.
Integration is always a context-bound activity. Points of integration vary across different
periods. As each program is operationalized, areas of integration may need to be
identified, validated and enriched. Moreover, even if the points of integration are not as
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comprehensive as desired, the framework provides the mechanism for addressing
overlaps and inconsistencies.
2. Multi-stakeholdership and consensus-building.
The PA 21 will be a document owned by various stakeholders in government and civil
society. Hence, the action agenda brings out the important roles of major groups and
other stakeholders in the sustainable development process.
3. Operationalization.
PA 21 must be identified with doing. This implies concrete policy statements as well as
appropriate implementation strategies on the critical issues that will affect sustainable
development in the Philippines in the next thirty years, including financing and localization
mechanisms. To facilitate operationalization, action measures are categorized into shortterm (1996-1998), medium-term (1998-2005) and long-term (2005-2025).
C. PA 21 Strategies
The journey towards sustainable development involves both a transition and a paradigm
shift. The Operational Framework for the Philippine Agenda 21, therefore, adopts a twopronged strategy in defining and mapping out the action agenda:
* creating the enabling conditions which would assist various stakeholders to integrate
sustainable development in their decision-making processes; and
* directing efforts at conserving, managing, protecting and rehabilitating ecosystems
through an approach that harmonizes economic, ecological and social goals.
This strategy is based on the premise that while strategic policy and paradigm shifts are
needed to operationalize sustainable development, the critical state of the country’s
various ecosystems--upland/forest, coastal and marine, freshwater, urban and
agricultural/lowland--demands and deserves urgent attention. On the other hand,
ecosystem-based actions cannot be sustained without an enabling environment. Creation
of an enabling environment is also an important requisite to building the capacity of all
stakeholders in making decisions in favor of sustainable development. As these changes
cannot be achieved overnight, an important dimension of the action agenda is, therefore,
the identification of courses of action that will help stakeholders manage the transition
towards sustainable development.
D. PA21 seeks to answer 4 questions
1. WHERE ARE WE NOW?
The Current and Emerging Landscape for Sustainable Development
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Achieving sustainable development is a formidable task. Hence, the journey towards
sustainable development must be grounded on a clear understanding of the challenges,
trends and opportunities that lie ahead.
a. Demographic Trends. The Philippines ranks as the 9th most populous country in
Asia and 1 4th in the world. The country's population growth, if unabated, will
double to 128 million by 2025. Rapid population growth and imbalances in spatial
distribution will continue if policy decision-making at all levels of governance does
not recognize the relationships among population, resources, environment and
development. The crucial role of the Filipino family in the dynamics of these
relationships should also be considered.
b. Cultural Trends. The inherent strengths of the Filipino culture (e.g. openness,
freedom of expression, resilience, strong family orientation ) continue to reinforce
social cohesion within the Philippine society. These values are also embodied in
the growing tradition of local activism. However, it has been observed that some
erosion of Filipino cultural values has taken place as manifested by, among others,
the commodification of indigenous culture, sexual tourism, consumerism and
increasing materialism.
c. Science and Technology Trends. There have been many positive developments
in this area. These include the improved level of contributions of highly skilled
Filipino scientists and the growing recognition of the value of indigenous science
and technology and holistic science. on the other hand, the sector has its share of
problems, such as: the “brain drain" phenomenon; unfair monopoly of intellectual
property rights; increasing use of technology as a simplistic response to complex
problems; poor quality of science education due to inadequate funding and
facilities; among others.
d. Economic Trends. Positive economic growth rates (as measured by GDP) have
benefited certain sectors of Philippine society but do not reflect social decline and
inequity nor the deterioration of the environment associated with economic growth.
Despite continued economic growth, challenges remain, which include, among
others: high level of public indebtedness; low level of savings; large deficits;
remaining distortions in the price and incentive system; rampant casualization of
labor; and indiscriminate land and ecosystem conversion.
e. Urbanization Trends. Difficulties in the implementation of agrarian and urban land
reform and rural development programs have contributed to unplanned and
uncontrolled urbanization. Philippine cities have deteriorated as human habitats,
beset with intractable and often interrelated problems like pollution, water shortage,
flooding, violence and other social ills.
f. Human Development Trends. Existing measures of human development indicate
some improvement over time. However, these improvements are uneven across
geographical, income, gender and ethnic groups. The development of human
potential is being affected by continuing challenges such as: rampant substance
abuse, break-up of families, economic exploitations and homelessness as
evidenced by the growing number of street children.
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g. Environmental Trends. Even with accelerating economic growth, environmental
quality is- fast deteriorating as dramatized by the increased incidence of
environmental disasters, problems associated with mine tailings, deforestation,
pollution, salt water intrusion and a host of other destructive activities. The
regenerative capacities of fragmented areas in the biogeographic zones that
nurture flora, fauna and natural resources are severely threatened. While
advances have been made in the area of biodiversity conservation alongside the
growing awareness of the role of indigenous peoples in maintaining the integrity
of ecosystems, the Environmental Impact Assessment system continues to be
plagued with various enforcement and compliance problems.
h. Institutional Trends. The Philippines has strong institutional building blocks for
sustainable development, including a strong civil society, socially and
environmentally- conscious business groups, community empowerment initiatives,
devaluation and decentralization. However, these are plagued by ineffective
mechanisms for enforcement and implementation, information inadequacies and
continuing systemic graft and corruption.
i. Political Trends. The current wave of globalization is increasingly posing some
threat to the country's national sovereignty. Domestically, the rich continue to
dominate political processes as evidenced by deep-seated iniquitous structures
and processes. The challenge continues for meaningful electoral reforms.
Meanwhile, the Local Government Code has reinforced the role of LGUs in
development administration. Civil society, as a countervailing force, has been
engaging government at all levels.
2. WHAT IS SUSTAINABLE DEVELOPMENT?
A Conceptual Framework for Sustainable Development
The World Commission on Environment and Development (WCED), in its report "our
Common Future" published in 1987, defines sustainable development as "meeting the
needs of the present generation without compromising the ability of the future generations
to meet their own needs".
While sustainable development derives its meaning from the global discourse, its
application must be rooted in the context of national realities and aspirations. The
Philippine Agenda 21's concept of development is grounded on both an image and a
shared vision of the Filipino society. It recognizes the key actors in sustainable
development as the government, business and civil society and the functional
differentiation of modern society into three realms--economy (where the key actor is
business), polity (where the key actor is government) and culture (where the key actor is
civil society). The three realms are interacting, dynamic and complementary
components of an integral whole.
Thus, the essence of sustainable development is in the harmonious integration of a sound
and viable economy, responsible governance, social cohesion/harmony and ecological
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integrity to ensure that development is a life-enhancing process. The ultimate aim of
development is human development now and through future generations.
3. WHERE DO WE WANT TO GO?
Elements of a Shared Vision
Philippine Agenda 21 envisions a better quality of life for all through the development of
a just, moral, creative, spiritual, economically vibrant, caring, diverse yet cohesive society
characterized by appropriate productivity, participatory and democratic processes and
living in harmony within the limits of the carrying capacity of nature and the integrity of
creation.
In concretizing the vision, Philippine Agenda 21 describes a path of images for individuals,
families, households and communities; for each ecosystem and across ecosystems in
consideration of the interaction of the various lifescapes and landscapes found therein.
The Philippine Agenda 21 adheres to the following principles of sustainable development:
Primacy of Developing Human Potential Holistic Science and Appropriate Technology
Cultural, Moral and Spiritual Sensitivity Self determination National Sovereignty Gender
Sensitivity Peace, order and National Unity Social Justice and Inter-, Intra-generational
and Spatial Equity Participatory Democracy Institutional Viability Viable, Sound and Broad
based Economic Development Sustainable Population Ecological Soundness
Biogeographical equity and Community Based Resource Management Global
Cooperation
4. HOW DO WE GET THERE?
Operational Framework and Action Agenda
The Operational Framework of Philippine Agenda 21 consists of a multilevel guide for
decision-making consisting of sustainable development criteria, parameters and
descriptors. The principles of sustainable development embodied in the vision serve as
the criteria which help define the viability of development interventions. The parameters
are basic policies from which the key ingredients of a sustainable development strategy
are developed. Sustainable development descriptors translate the parameters into
specific action strategies.
Operationally, sustainable development is development that draws out the full human
potential across ages and generations. It is, at the same time, ecologically friendly,
economically sound, politically empowering, socially just, spiritually liberating, gender
sensitive, based on holistic science, technologically appropriate, builds upon Filipino
values, history, culture and excellence and rests upon strong institutional foundations.
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Philippine Agenda 21 provides a comprehensive set of economic, political, cultural
scientific and technological, ecological, social, and institutional parameters that flow out
of the principles of sustainable development. Development is sustainable if it is fully
guided by these parameters.
Philippine Agenda 21 advocates a fundamental shift in development thinking and
approach. It departs from traditional conceptual frameworks that emphasize sector based
and macro-concerns. Philippine Agenda 21 promotes harmony and achieves
sustainability by emphasizing:
a. A scale of intervention that is primarily area-based. The national and global policy
environment builds upon and support area-based initiatives.
b. Integrated island development approaches where applicable. This recognizes the
archipelagic character of the Philippines which includes many small island
provinces.
c. People and the integrity of nature at the saltier of development initiatives. This
implies the strengthening of roles, relationships and interactions between
stakeholders in government, civil society, labor and business.
d. Basic sectors have an important role to play in achieving equity and in managing
the ecosystems that sustain life.
The action agenda of the Philippine Agenda 21 elaborates the mix of strategies that
integrate the SD parameters in the country's overall development strategy. In formulating
the action agenda, PA 21 has been guided by the key concepts of integration, multistakeholdership and consensus building and operationalization.
PA 21 does not duplicate but builds on existing and ongoing initiatives related to
sustainable development. Hence, sustainable development in the Philippines is the
accumulation of conceptual and operational breakthroughs generated by the Philippine
Strategy for Sustainable Development, Social Reform Agenda, Human and Ecological
Security, among others. Sustainable development is also a product of the process itself,
of engaging various stakeholders and of working in global national and local arenas.
The PA 21 is a document owned by various stakeholders in government and civil society.
Hence, the action agenda brings out the important roles of major groups and other stake
holders in the sustainable development process.
PA 21 must be identified with doing. This implies concrete policy statements as well as
appropriate implementation strategies on the critical issues that will affect sustainable
development in the Philippines in the next 30 years, including financing and localization
mechanisms.
The journey towards sustainable development involves both a transition and a paradigm
shift. Philippine Agenda 21, therefore, adopts a two pronged strategy in defining and
mapping out the action agenda:
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a. creating the enabling conditions which would assist various .stakeholders to
manage the transition and at the same time build their capacities towards
sustainable development;
b. direct and proactive efforts at conserving, managing, protecting and rehabilitating
ecosystems through an approach that harmonizes economic, ecological and
social goals.
Managing the transition to SD calls for interventions in the following areas:
a.
b.
c.
d.
e.
integrating SD in governance
providing enabling economic policies
investing in human and social capital
mapping out a Legislative Agenda; and
addressing critical and strategic concerns, to include: population management,
human health, food security, human settlements and land use.
These interventions define the Philippine Agenda 21's action agenda across ecosystems.
The action agenda at the level of ecosystems consists of strategic and catalytic
interventions covering the following ecosystems and critical resources:
1. ECOSYSTEMS
a. forest/upland ecosystem
b. coastal and marine ecosystem
c. urban ecosystem freshwater ecosystem
d. lowland/agricultural ecosystem
2. CRITICAL RESOURCES
a. minerals
b. biodiversity
CHALLENGES AHEAD in Implementing PA 21
The implementation of Philippine Agenda 21 must be anchored on the basic principle of
collective choices and responsibility. Forging new partnerships and finding areas of
common ground for collaborative action are central to the process of implementation as
well as building and strengthening the roles and capacities of major groups and
stakeholders; a consolidated and well-coordinated effort at information, education and
communication advocacy; localization; generating financing means and strategies; and
monitoring and assessment.
1.
Strengthening the Role of Major Groups. The identification of key players and how
they interact in the whole process provide a basis for deepening the analysis and
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treatment of the ecosystem, and also for defining the varying roles that various
stakeholders are expected to play for achieving sustainable development.
There are two major categories of stakeholders: basic sectors and intermediaries.
Basic sectors comprise the farmers and landless rural workers, fisherfolk, indigenous
peoples, urban poor, and other disadvantaged groups such as workers in the informal
sector, children and youth, persons with disabilities, elderly, disaster victims and
overseas contract workers. Intermediaries are composed of formal institutions that
include the national and local government units, business and private sectors, nongovernment organizations, church-based organizations, civic groups and
professional associations, mass media and the international community.
The key roles of the major stakeholders are defined according to sectoral needs,
motivation or interest and perspectives. Intermediaries can serve as any of the
following: (a) brokers of information and appropriate technologies; (b) mobilizers of
resources; (c) net workers to strengthen institutional linkages, trainers; and (d)
product enhancers.
Basic sectors, on the other hand, can serve as advocates of specific issues and
concerns, organizers and mobilizers of community resources, culture bearers,
innovators of indigenous approaches and systems, managers and controllers of
community resources.
There are common grounds within which these key actors can undertake
collaborative actions and interventions.
2. Localization. The process of localizing Philippine Agenda 21 is a vital element in
mainstreaming the action agenda at the local level. In principle, localization shall
seek to emulate the following key concepts: multistakeholdership and consensus
building, integration and operationalization while respecting the need to preserve
the peculiarities inherent in each locality.
The process of localization needs a structure that will ensure coordination and
cooperation among the various actors. The structure to be eventually adopted
shall be left to the discretion of the local people. Two options, though, can be
identified: tapping existing structures such as the Regional Development Council;
or creating a separate structure which is a mirror image of the PCSD.
3. Financing Means and Strategies. The adoption of a mixture of market-based
instruments and command and control measures is expected to set into motion
financial flows that would help achieve the goals of the PA 21. The strategy aims
not only to mobilize funds to support PA 21 activities. More importantly, it aims to
help induce changes in production and consumption patterns in favor of the
sustainable management of the country's resources.
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Financing PA 21 will have to rely heavily on the economic sectors' ability and
willingness to incorporate sustainable development principles in the design of their
production systems. Market based instruments working in tandem with the
application of beneficial and realistic environmental standards through credible
enforcement of regulations and sanctions could encourage companies to invest in
abatement equipment.
Companies that support philanthropic activities can also be tapped by Philippine
Agenda 21 to channel an increasing share for SD initiatives under an environment
fund. Pollution charges and other forms of penalties and fines can be collected at
rates that will provide an incentive for environmental protection. PA 21 may a1so
be considered for inclusion in the Investment Priorities Plan to make
environmental investments eligible for fiscal incentives.
Proponents of public and private investment ventures are primarily responsible for
making the needed investments for environmental rehabilitation and/or mitigation
in compliance with environmental standards. Incorporating such investments in
public sector projects can be ensured through government's appraisal procedures.
4. Information, Education and Communication. The imperatives of sustainable
development necessitate a reorientation in the fundamental values of society.
Hence, the formulation and implementation of a comprehensive information,
education and communication advocacy plan is part of the efforts to mainstream
the principles of PA 21 in the various efforts of all stakeholders.
The IEC Plan for PA 21 would involve a mix of communication strategies such as:
social mobilization, advocacy, social marketing, networking and visioning. The
following are some of the strategic messages which shall form the basis of the
overall strategy:
Sustainable development is a matter of survival.
The only true development is sustainable development.
Avoiding pollution is not necessarily avoiding profit.
Pollution does not pay, Managing pollution pays.
Environmental protection is a corporate responsibility.
Sustainable development begins and ends with you.
5. Monitoring and Assessment. To effectively assess the implementation of
Philippine Agenda 21, a comprehensive monitoring, evaluation and reporting
system should be established to guide all stakeholders to meaningfully participate
in the process of operationalizing sustainable development. Such a system will
also help institute broad-based accountabilities and responsibility for sustainable
development among members of society. This .system may include the following
elements: (a) a system to coordinate and evaluate the extent to which the
Philippine Agenda 21 has been adopted and implemented by all stakeholders; (b)
a system to coordinate, support and enhance existing national and loca1
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multisectoral as well as sectoral monitoring, evaluation and information exchange
on the implementation of initiatives related to Philippine Agenda 21; and (c) a
system for reporting, feed backing and utilizing the monitoring and evaluation
results on Philippine Agenda 21 for international, national and local stakeholder
communities.
Resources:
1. https://seniorsecondary.tki.org.nz/Social-sciences/Education-forsustainability/Learningobjectives#:~:text=and%20experience%20to%3A-,Knowledge%20and%20under
standing,initiatives%20for%20a%20sustainable%20future.
2. https://www.un.org/esa/agenda21/natlinfo/countr/philipi/inst.htm#:~:text=The%20
Philippines%20has%20also%20established,in%20their%20decision%2Dmaking
%20processes.
3. https://sedac.ciesin.columbia.edu/entri/texts/a21/a21-25-children-and-youth.html
4. Robinson, N. A. (2004). Strategies toward sustainable development:
Implementing Agenda 21. Dobbs Ferry, NY: Oceana Publications.
5. Agenda 21. (1992). New York: UN.
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Final Output (50 Points)
1. Read the “Tragedy of the Commons” by Garret Hardin
a)
What is the tragedy of the commons according to Hardin? (5 points)
b)
What is Hardin’s solution to the Tragedy of the Commons? (5 points)
2. How is Philippines affected by climate change? Cite and explain five (5) evidencebased examples in 30-50 words per example. (5 points each).
3. Enumerate 3 ways on how you can contribute to mitigating or solving problems
related to environmental degradation. Explain each way in not less than 3 sentences. (5
points each)
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