Environmental Problems, Their Causes, and Sustainability - Environmental Science - page 8

services such as nutrient recycling and climate control
(including precipitation) renew natural resources such
as topsoil and underground deposits of water (aqui-
fers). Sustainability means living off such biological
income without depleting or degrading the natural
capital that provides this income.
The second step toward sustainability is to recog-
nize that many human activities degrade natural capital
by using normally renewable resources faster than na-
ture can renew them (Figure 1-2, Step 2). For example,
in many areas our activities erode essential topsoil
faster than it can be renewed. And we withdraw water
from some underground deposits (aquifers) faster
than they are renewed by precipitation from nature's
climate system. We also cut down (clear-cut) or burn
diverse natural forests to grow crops, graze cattle, and
supply us with wood and paper.
This leads us to search for solutions to these and
other environmental problems (Figure 1-2, Step 3). For
example, a solution might be to stop clear-cutting di-
verse mature forests.
The search for solutions often involves conflicts,
and resolving these conflicts requires us to make trade-
offs, or compromises (Figure 1-2, Step 4). To provide
wood and paper and crops such as coffee, for exam-
ple, we can promote the planting of tree and coffee
plantations in areas that have already been cleared or
degraded.
In the search for solutions, individuals matter.
Sometimes one individual comes up with an idea for
bringing about a solution. In other cases, individuals
work together to bring about the political or social
changes necessary for solving the problem (Figure 1-2,
Step 5). Some individuals have found ways to elimi-
nate the need to use trees to produce paper by using
residues from crops (such as rice) and by planting
rapidly growing plants and using their fiber to make
paper. Other individuals are working politically to
persuade elected officials to ban the clear-cutting of
ancient forests while encouraging the planting of tree
and crop plantations in areas that have already been
cleared or degraded.
The five steps to sustainability must be supported
by sound science —the concepts and ideas that are
widely accepted by experts in a particular field of the
natural or social sciences. For example, sound science
tells us that we need to protect and sustain the many
natural services provided by diverse mature forests. It
also guides us in the design and management of tree
and coffee plantations.
Moving toward sustainability also involves inte-
grating information and ideas from the physical sci-
ences (such as chemistry, biology, and geology) with
those from the social sciences (such as economics, poli-
tics, and ethics). To show this integration, most sub-

headings throughout this topic are tagged with the
terms science, economics, politics, and ethics, or some
combination of these words.

Environmentally Sustainable Societies
An environmentally sustainable society meets
the basic resource needs of its people indefinitely
without degrading or depleting the natural capital
that supplies these resources.
An environmentally sustainable society meets the
current needs of its people for food, clean water, clean
air, shelter, and other basic resources without com-
promising the ability of future generations to meet
their needs. Living sustainably means living off natural
income replenished by soils, plants, air, and water
and not depleting or degrading the earth's endow-
ment of natural capital that supplies this biological
income.
Imagine you win $1 million in a lottery. If you in-
vest this money and earn 10% interest per year, you
will have a sustainable annual income of $100,000
without depleting your capital. If you spend $200,000
per year, your $1 million will be gone early in the sev-
enth year. Even if you spend only $110,000 per year,
you will be bankrupt early in the eighteenth year.
The lesson here is an old one: Protect your capital
and live off the income it provides. Deplete, waste, or
squander your capital, and you will move from a sus-
tainable to an unsustainable lifestyle.
The same lesson applies to our use of the earth's
natural capital. According to many environmental sci-
entists, we are living unsustainably by wasting, de-
pleting, and degrading the earth's natural capital at an
accelerating rate.
Some people disagree. They contend that the seri-
ousness of human population, resource, and en-
vironmental problems has been exaggerated. They
also believe we can overcome these problems by
human ingenuity, economic growth, and technological
advances.

1-2 POPULATION GROWTH,
ECONOMIC GROWTH, AND
ECONOMIC DEVELOPMENT

Human Population Growth
The rate at which world's population is growing has
slowed but is still increasing rapidly.
Currently, the world's population is growing expo-
nentially at a rate of about 1.2% per year—down from
2.2% in 1963. This may not seem like a very fast rate,
but it added about 78 million people (6.5 billion