Introduction to
Geography
People, Places, and Environment, 6e
Carl Dahlman
William H. Renwick
Chapter 4: Biogeochemical Cycles
& the Biosphere & the Four Laws
of Ecology
Holly Barcus
Morehead State University
And Joe Naumann
UMSL
Biomes
• Global patterns in the biosphere
– Associations of plant and animal types
– Similar distributions: highly interconnected
• Soil
• Vegetation
• Climate
– Human impacts
• Population growth
• Consumption of natural resources
2
Recycled & Recycling World
• Studying patterns
and relationships,
one discovers that the
world is one gigantic
system composed of
intrerconnected and
interdependent
cycles and subsystems.
• Everything &
everyone is
connected!
3
Solar Powered World
• Directly or
indirectly, all
the
biochemical
systems
depend on
the energy
from the sun.
4
Cycles & Balances
• The state of the earth today is the result of past
actions, creating a somewhat stable, selfperpetuating ecosystem (at least in human terms).
In that system, we can identify cycles (and
recycling) and balances that help perpetuate the
“climax” condition.
• Human actions can fit in two ways:
– Respect cycles & balances and work with them
– Upset the cycles & balances to obtain short-term
benefits & then deal with the consequences.
5
Systems
• System: any working thing composed of two or
more interrelated parts
– Closed System: is self-maintaining or perpetuating –
doesn’t need something to start or maintain it.
Example: Hydrologic cycle
– Open System: needs something to start or maintain
its operation. Example: an automobile
• The entire earth may be seen as a complex,
gigantic ecosystem composed of many
interconnected subsystems.
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Biogeochemical Cycles
• Recycling processes that supply essential
substances to the biosphere
– Connect Earth’s subsystems
• Atmosphere, hydrosphere, lithosphere
• Law of conservation of energy and matter
– states that energy cannot be created or
destroyed, but can change its form. The total
quantity of matter and energy available in the
universe is a fixed amount and never any more
or less.
• Two important biogeochemical cycles
– Hydrologic
– Carbon
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Key Cycles
• Rock Cycle (see chapter 3)
8
Hydrologic Cycle
• Flows of water among land, sea and air
• 3 states of water
– Gas
– Solid
– Liquid
• All living things are primarily water
9
The range of earth temperatures allows water
to exist in all three states.
Water: Where is it?
•
•
•
•
•
•
96.5% stored in oceans
2% stored in glacial ice
0.9% is saline groundwater
0.8% available as fresh water
0.014% in rivers and lakes
0.001% is contained in the atmosphere
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Water Budget
• Accounting of inflows and outflow within a given
system
• Evapotranspiration
– Sum of evaporation and transpiration
– Seasonal variation
• Low in winter
• High in summer
• Local water budgets
– Compares precipitation and evapotranspiration
13
Generalized Water Budget:
Water Budget
• Variations reflect the
different budgets that
exist in different
climates in different
locations around the
world.
Soil and the Water Budget
• Critical to water budget: soil stores and makes
water available to plants.
• Stores water for evapotranspiration (ET)
– Soil texture & composition affect how much water soil
can hold
• Size of soil particles
• Quantity of humus (organic matter)
• Degree of compaction
• Infiltration capacity
– Good -– Poor --
16
Vegetation and Hydrologic Cycle
• Trees and forests require large amounts of water
• Trees play key role in returning rainwater to the
atmosphere – and oxygen
– Deforestation affects water balance of regions
• Reduces evapotranspiration
• Promotes a less humid climate – climate change
– Ex. Amazon & Congo basins
• Grasses – produce less oxygen than forests
– Shallow roots
– Variable transpiration rates
17
The Carbon Cycle
• Processes that cycle carbon and oxygen
between the environment and living things
– Photosynthesis
• Determined by climate
• Seasonal cycles of solar radiation
– Respiration
• Opposite reaction of photosynthesis
– Combustion
• Coal, oil, natural gas
• Industrial Revolution
• Lithosphere stores carbon
18
Most Life is based on carbon
Nitrogen Cycle
• Nitrogen is essential for plant growth
20
21
22
Food Chain
23
Food Chain Cycle Related to Seasons
• Stage 1
24
Aphids Stage 2
25
Aphids Stage 3
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Deforestation (particularly tropical rainforests)
• Important influence on biosphere-atmosphere
exchanges
• Biomass
–
–
–
–
Stores carbon & releases oxygen
Forests and trees are key storage sites
Forests filter impurities from the atmosphere
Deforestation through cutting and burning releases
carbon into atmosphere
• Critical regions
– Central and South America
– West Africa
– Southeast Asia
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Soil
• Dynamic, porous layer composed of weathered
mineral matter, organic matter (living & dead),
water and air. Soil is a “living thing.”
• 5 factors that affect soil properties
–
–
–
–
–
Climate
Parent material
Biological activity
Topography
Time
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Soil Formation
• Weathering
– Mechanical and chemical
• Water
– Volume that passes through rock is important factor
– Large volumes of water = lower amounts of soluble
minerals
• Plant and animal activities
• Topography
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Soil Characteristics
• Six principal components of soil
–
–
–
–
–
–
Rocks and rock particles
Humus
Dissolved substances
Organisms
Water from rainfall
Air
• Soil horizons
– Layers of substances found in soils
– Formed through vertical movement of water, minerals
and organic matter
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Topsoil
Types of Soils
• Soil orders (related to climate & vegetation – a
relatively stable symbiosis in nature)
– 11 orders
• 47 suborders
• 230 great groups
• 1,200 subgroups
• 6,000 families
• Thousands of soil series
• USDA Natural Resource Conservation Service
maps
33
Climatic Soil Regions
• Humid tropical and subtropical soils
– Oxisols and ultisols
– Highly weathered & leached - practically no humus
accumulation
• Arid region soils
– High in soluble minerals & very little humus
• Midlatitude humid soils
– Moderately leached
– Moderate amount of humus
• Midlatitude subhumid soils
– Fertile – high humus content – “Chernozem”
– Associated with grain-producing regions
34
Soil Regions of the World
Differing climate & vegetation =
different soil types
• How much
humus?
• Acid,
neutral, or
base?
• What
texture?
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Soil Problems and Fertility
• Problems
– Artificial nutrients not replaced fast enough
• Manure, inorganic fertilizers
• High intensity agriculture
– Erosion and desertification – highly related to human
use/abuse
• Fertility
– Factors = plowing, planting cycles, availability of
nutrients
– Restoration of fertility
• Fallow periods
• Organic and inorganic fertilizers
• Concern about soil degradation and future food
production capacity
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The Four Laws of Ecology
• Human survival may depend on humans
understanding and valuing these laws and
in considering them whenever decisions
affect the environment.
38
Four Laws of Ecology: From Barry
Commoner’s book The Closing Circle
• Everything is connected
– Everything on earth is interconnected much like a
huge spider web
• Everything goes somewhere
– Elements of the system may change but don’t cease
to exist
• Nature knows best
– What nature creates is biodegradable
• There’s no such thing as a free lunch
– There are consequences (costs) for every action
39
Everything is Connected
• It may take some time to see some connections.
40
Everything Goes Somewhere
• Winter road salt contaminates ground water, eventually causing 41
damage far away.
Nature Knows Best
• Non-biodegradable
chemicals remain in
the ecosystem
indefinitely, being
recycled through the
food chain over and
over and over.
42
There’s no such thing as a free lunch!
• Action: clear cutting by lumber companies
43
Clear Cutting Consequence: mudslide
resulting from clear cutting – costs to
repair damages
44
1.
DDT molecules in the ocean are
ingested by plankton, storing
DDT
2.
Plankton eaten by small fish,
storing & concentrating DDT
3.
Small fish eaten by larger fish,
storing & concentrating DDT
4.
Larger fish eaten by seagulls,
storing & concentrating DDT
5.
Seagulls produce thin-shelled
eggs – no chicks hatch
6.
7.
Seagull
Example
3
2
1
Eggs decompose and DDT
returns to soil or water to be
absorbed at the food chain base
and start another cycle
Seagull dies returning DDT to
soil or water to be absorbed at
the food chain base and start
another cycle -- #8
8
4
DDT is
nonBiodegradable
and recycles.
7
6
5
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Ecosystem
• Includes all living organisms and the physical area
in which they exist
• Fundamental elements
–
–
–
–
Producers
Consumers
Decomposers
Material/energy needed for production
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Food Chains
•
•
•
•
•
•
Distribution
Herbivores
Carnivores
Omnivores
Trophic level (Place in the food chain)
Biomagnification
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Biological
magnification
• Generally, the higher a
species is on the food
chain, the greater the
magnification of “stored”
chemicals.
• Humans are at the top of
the food chain
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Why understand the 4 laws?
• Every change in the ecosystem has
consequences
• In the past the consequences were relatively
small and we could learn from our mistakes
• The technology of today makes it possible for us
to make changes with possibly catastrophic
consequences
• We must try to ascertain possible consequences
before we initiate changes in the ecosystem
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The Reality of the 4 Laws
52
Example
• Pollution of the oceans plus the thinning of the
ozone layer could be harmful to the
phytoplankton (and zooplankton) in the sea
– Phytoplankton (microscopic plants) form the basis of
the entire food chain of the ocean
– Phytoplankton produce much oxygen (I’ve read
estimates as high as 70% of the oxygen produced
come from the phytoplankton)
• Do we really want to risk harming
phytoplankton? A mistake can’t be easily
undone!
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Four Requirements of Life
All life on earth
depends on four
requirements:
1.
Sunlight – the
power source or
enabler for the
life system
(climate, plants,
animals, etc.)
2.
Water
3.
Air
4.
Soil (land)
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Pyramid of Life
• A change at
any level may
have serious
consequence
s for
everything
above it on
the pyramid.
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Community Succession
• Sequence
• Succession
• Climax community
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Biodiversity
• Diversity of species
• Stability of community
• Biosphere reserves
– UN Biosphere Reserve Program
• Importance of size
• Managed landscapes
57
Biodiversity is essential
• Do we know the
niche of each
member of a
biotic community?
• Gene pool for
future hybrids
• Undiscovered
values – don’t
throw out baby
with the bath
58
Biodiversity on a Coral Reef: Click
the picture for the video
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Biomes
• Ecosystems grouped by:
– Plant types
– Animal types
• Named for dominant vegetation/climate
• Typically contain many ecosystems
60
Major Biomes
• Forest
– Tropical & temperate rainforest
– Boreal
•
•
•
•
•
•
Savannah
Woodland
Scrubland
Grassland
Desert
Tundra
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Tropical Rainforest Biome
• Click the picture to see the video
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Desert Biomes
• Click the picture to see the video
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Biomes - Bioregions
Human and Natural Effects
• Humans influence ecosystems
– 37% of land area = cropland or pasture
– Desertification
• Local topography and geology
– Vegetation and evapotranspiration vary regionally
– Wind erosion
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Dangers to Biochemical Systems
and Cycles from Human Actions
•
•
•
•
Desertification
Deforestation (particularly tropical)
Loss of biodiversity
Threats to the base of the food chain
– Eutrophication
– Pollution
– Over fishing
• Soil: erosion & salinization
• Global Warming & ozone depletion
• Water & air pollution
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Changing the “Mix” of a Biome
• Subtraction from a biome
– Removing a species
– Removing or altering a natural condition
• Adding to a biome
– Introduction of exotic plants
– Introduction of exotic animals
– Introduction of exotic diseases
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Removing species
• Predators in North County & most of MO
– Deer
– Rabbits & squirrels
• Removing forest fires?????????
– Jack pine
• Crocodiles in African rivers
• Removing a vital link in the biome may
remove all that was dependent on it.
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Introducing Exotics
•
•
•
•
Rabbits in Australia
Kudzu in USA
Fungus carrying moth in USA
Smallpox, diphtheria, whopping cough,
syphilis, “childhood diseases” etc., to the
Americas
– Danger today of terrorists using exotic
microbial agents as weapons
• Historians call this the Columbian
Exchange!
69
Saltcedar: shrub native to
Eurasia & Africa
• 12 varieties in USA – natural, vigorous hybrid
• Long taproot depletes springs in US West
• Salt accumulates on leaves – when leaves fall, soil
becomes to salty for native plants
• Vigorous grower – crowds out native plants
• Threatens habitat of 31 endangered species
• Spreading to 40,000 acres per year
• Resists fire & chemical sprays - insects (hybrid)
• Clogged California rivers
• Displaced shorebirds in Kansas
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Land Use
in the
USA
Human Interaction with Water Upsets
Many Cycles
72
Water & Water Quality
•
•
•
•
Availability of Water
Modification of Streams
Water Quality
Agricultural Sources of Water Pollution
– Fertilizers, Biocides, Animal Wastes
• Other Sources of Water Pollution
– Mining & Industry
– Municipalities and Residences
• Controlling Water Pollution
73
Modification of Streams
• Levees increase flooding downstream
and across the river.
• “straightening” streams increases the
volume of water downstream
• Dams may impede the movement of
fish – fish ladders needed for salmon
in northwest
• Canals connecting streams may allow
the spread of undesirable species –
zebra mussel and sea lamprey
• Destruction of wetland habitats
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Levee – modifications of streams
Levee
More
flooding
Man-made
levees are
higher than
natural ones.
• The floodplain (basin) is nature’s release valve for floods
and provides a wetland habitat for many species of plants
and animals. A levee reduces its ability to moderate flooding
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and sustain a wide variety of plants and animals
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Water Quality
• Nature pollutes water at a rate which
nature can process in a reasonable time
and/or distance from the contamination.
– Animal feces
– Decaying plant and animal material
• Humans have overloaded the natural
system and that is what we call “pollution.”
– More than nature can process in a reasonable
time and/or distance
– Non-biodegradable chemical compounds
78
Sources of Water Contamination
• Microbiological contamination
– septic tanks & sewage discharges
– sanitary landfill sites
– farms (liquid manure storage, animal production)
• Chemical contamination
– septic tanks (organic contaminants, disinfectants,
etc.) & sewage discharges
– sanitary landfill sites
– farms (fertilizers, pesticides, herbicides)
– leakage from oil tanks or chemical spills
– highways (de-icing salt)
79
Water Quality continued. . .
• Agricultural run-off creates problems
– Causes excessive growth of algae and other plants, leading to
eutrophication
– Nitrate build-up in reservoirs threatening the life of infants and very
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ill persons – nitrates to nitrites.
Urban Run-off Contributes More to Flooding
Natural surface
Urban surface
• Farmland and natural land retains water longer,
releasing it more slowly to the streams
• Urban surfaces are non-absorbent of water and
produce greater volumes of run-off more rapidly
81
Urban -- Rural
• Consider this: In most urban areas, the finest, level farmland
is used to build subdivisions, shopping malls, etc. – retiring
the best farmland and increasing runoff/flooding.
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Damage to the seas and delicate
biomes like the tundra
84
Danger at sea
Accidental oil spills can harm the sea biome
and nearby coastal biomes.
85
Each Citizen Has a Role to Play
• Different world views cause cultures to
respond to nature, the physical world, in
different ways – some life-affirming and
others life-negating.
86
Many problems
don’t start within
or stop at our
borders!
End of Chapter 4
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