Environmental Problems and Their Causes
I: Exponential Growth: The root cause of our environmental problems.
Exponential growth - value of something increases by a fixed percentage of the whole each time (i.e. 5% per year).
Starts off slowly, but eventually increases very rapidly. Produces a J-shaped curve of value versus time. Initial
increase is often less than for linear growth where the increase is a fixed amount for each time increment. The
same kind of growth is happening to the world's human population.
Took ~2 million years to reach a human population of 1 billion, 123 more years to reach 2 billion (early 20th
century), 33 more years to reach 3 billion, 14 more years to reach 4 billion, 13 more years to reach 5 billion, 12
more years to reach 6 billion in 1999. Projected to have ~7 billion by 2013, ~8 billion by 2028, and ~9 billion by
2050. Population growth is leveling off.
Essentially all of the environmental problems we face are increasing exponentially. These include not just
population growth, but also resource demand, loss of natural habitats, rates of extinction, poverty increase, levels
of pollution.
Doubling time of any value can be determined by the rule of 70: DT=70/% growth rate. If rate of increase is 10%
per year, doubling time is seven years. If 5%, doubling time is 14 years
World's population is increasing at approximately 1.2% per year. Means it will double in less than 60 years. Present
population is ~ 6 billion and will reach ~9 billion by 2050. Average hourly population increase is about 9,000.
II: Inequitable Distribution of Economic Wealth and Population.
Developed Countries (First World): Highly industrialized with per capita GNPs above $4,000. Include U.S., Canada,
Europe, Japan, and Australia. Accounts for 20% of the world's population, but have 85% of the world's wealth, use
88% of the world's resources (coal, oil, metals, etc.), and generate 75% of the world's waste and pollution.
First World population growing at only about 0.1% per year (700 year doubling time)
Developing Countries (Second and Third World): Low to moderate industrialization with per capita GNPs as low as
$350. Africa, Asia, and South America. 80% of the worlds population, 15% of wealth, 12% of resource use.
Growth rate is about 1.7% per year (doubling time is about 41 years!). Accounts for 95% of the world population
increase.
Those countries least able to afford increasing populations are those growing the fastest!!!
The rich get richer, the poor get poorer. This disparity can lead to disease, famine, increased resource depletion,
pollution, worker exploitation, uncontrolled population migrations, political upheavals, terrorism, and armed
confrontations.
III: Sustainability and Resources.
Our existence depends on energy and materials derived from the sun and earth.
Energy from the sun = solar capital. Earth materials (air, water, soil, wildlife, minerals, habitats, surface processes)
= earth or natural capital.
A sustainable society lives off this capital without depleting it. Once capital is used up our existence is imperiled.
However, as population increases, as well as standards of living, we use our earth capital up at an ever accelerating
rate (remember exponential growth).
Can we sustain our present population? What about twice our present population? Can we increase everyone's
standard of living? Can we sustain ever-larger populations with ever-higher standards of living without running out
of earth capital? What is the human carrying capacity of the earth?
One of the determining factors in answering these questions is how much natural resources we have to support
our lives and societies.
Resource: anything from the natural environment we use to meet our needs or wants. These may change over
time (whale oil versus crude oil). Three broad types:
Renewable resource: constantly being replenished (solar and wind energy). There is an inexhaustible supply.
Potentially renewable resource: replenished on a human time scale (less than several decades). Include trees,
crops, surface waters, and biodiversity (genetic, species, and ecological). Must know its sustainable yield
(replenishment time) and use this type of resource at a slower rate than that if we do not want to deplete it.
Nonrenewable resources: replenished on a geologic time scale (100-1,000-millions of years). That is, for our
purposes there is a finite amount of the resource and once it is used up it's gone. We can't wait around for it to be
replenished. We will eventually run out. Includes fossils fuels, mineral resources, soil, and groundwater.
Nonrenewable resources typically have a bell shaped production history curve. Become economically
depleted when 80% of the resource has been used up (remaining 20% to expensive to exploit). Can extend
production curve by utilizing the four R's of resource use:
1) Refuse (don't use)
2) Reduce (use less)
3) Reuse (use the same thing over and over again)
4) Recycle (make new products from material)
Can't use last two with energy resources (once burned can't burn it again).
Reserves: That portion of the total nonrenewable resource that can be economically exploited. Can go up or down
according to market conditions. As reserves dwindle price will go up making more of the remaining resource part
of the reserves.
IV. Pollution.
Pollution: anything that negatively impacts the air, water, soil, or food. Harms the health, survival, or activities of
humans or other living organisms. One person's pollution may be another's resource.
May be liquid, solid, gas, or energy (heat, radiation). Usually produced as the result of the utilization of resources.
May be naturally occurring or anthropogenic (human produced). May be from an identified point source (a
smokestack) or from a dispersed non-point source (fertilizer runoff). Usually easier and cheaper to control point
source pollution.
Effect of pollution depends on three factors:
1) Toxicity or chemical reactivity. How harmful is the material?
2) Concentration (ppm, ppb, etc.). A very small amount of a highly toxic substance may be of greater concern than
a lot of something relatively benign.
3) Persistence (degradable or non-degradable). Does the material break down to a harmless substance(s) or does
it remain unchanged indefinitely.
How you deal with a pollutant depends on a combination of these three factors.
Two major possibilities:
1) Pollution prevention (input control). - Keep it from ever reaching the environment (proactive). Done by refuse,
reduce, reuse, and recycle). Treat problem.
2) Pollution cleanup (output control). - Get rid of the pollution after it has entered the environment (reactive).
Treat symptom. Often this is harder and more expensive to do than prevention.
However, at the present time, 99% of environmental spending in the U.S. is for cleanup.
V. Evaluating Environmental Impact: The PAT Model.
Simple model of evaluating a populations impact on the environment can be determined if three factors are
known:
1) Population (P) - number of people.
2) Affluence (A) - standard of living or per capita use of resources.
3) Technology (T) - amount of pollution produced per unit of resource used.
P x A x T = Total Environmental Impact.
Developed Countries: Low P, High A and T: Consumption-driven pollution.
Developing Countries: High P, Low A and T: Population-driven pollution.
A more realistic model of evaluating environmental impacts is much more complex.
VI. Changing Human Environmental Impacts
Over the course of human history our impact on the environment has changed as human culture has changed.
Until 12,000 years ago humans were hunter-gatherers: nomadic people who ate wild plants, meat, fish, and also
scavenged. Lived in small bands (family groups typically of less than 50 people), which migrated from place to
place in a constant search for food. Life spans were 30-40 years. Because of very high infant mortality populations
grew very slowly.
Impact on their environment was minimal and local. Most impacts were often of short duration (they moved on)
and reversible by natural processes (due to small number of individuals)
Starting about 12,000 years ago an Agriculture Revolution began. People in Asia, Africa, and the Americas began
to concentrate in permanent communities, cultivate wild plants (corn, wheat, etc.), and domesticate wild animals
(cattle, fowl, etc.).
Early agricultural practices included slash-and-burn cultivation, shifting cultivation, and subsistence farming.
Again, environmental impacts were small and often recoverable. Later practices included use of beast-of-burden,
metal tools, and irrigation. Increased the amount of land that could be cultivated, type of plants grown, yields, and
as a result, birth rates, life expectancy, and the impact of people on the environment also increased.
People began to accumulate material goods (didn't have to carry them) and could now grow more food than they
could eat. Commerce resulted, cities began, conflicts between city-states and cultures increased, and the natural
environment (wild plants and animals) began to be seen as a nuisance and not a necessity.
More people needed more food and wood (fuel and shelter), so large areas of forest were cut down destroying
habitats and increasing rates of extinction. Soil was lost and fertile areas became barren and desert-like. Other
resources (metals and other minerals) were in greater demand and the amount of waste (agricultural and human)
increased, fouling waterways.
The Industrial Revolution began in England in the mid-1700s and the U.S. in the early 1800s. Caused a huge
increase in per capita energy consumption. Production of goods increased rapidly. Fueled initially by wood and
flowing water (potentially renewable), then coal and then oil and natural gas. Latter three are all nonrenewable
fossil fuels.
Production of goods switched from localized, small-scale sites (home) to centralized, large factories located in
rapidly growing cities. Populations shifted from rural to urban. Farm machinery, fertilizers, and genetic engineering
increased crop yields. Fewer acres produced more food. Mass production techniques led to the cheap availability
of mass consumer goods requiring huge amounts of natural resources and producing equally large amounts of
waste and pollution.
However, people also now enjoy longer and healthier lives because of more food, lower infant mortality, and
better sanitation, hygiene, nutrition, and medical care. Modern, advanced technological societies provide the
highest standard of living, but also cause the most damage to the natural environment.
Are we now in the midst of an information revolution? Will it lead to more or less environmental degradation?
What about the use of more or less resources/person? Or the production of more or less pollution/person? Don't
really know the answers to these questions at this time.
VII. So What Is Our Present Situation?
At the simplest level, there are two very different views of present environmental conditions (Table 1-1). One
believes humans can overcome anything, the other that humans will ruin everything. Also read the two scenarios.
The truth may lie somewhere between these two views.
Which you believe depends on your worldview and the place of humans in the world. Perhaps it also depends on
whether you're an optimist or pessimist.