HUMAN BIOLOGY

hUMaN iMpaCts oN the Biosphere 475

ecological footprint The

total resources a population

consumes and the wastes it

produces.

nonrenewable resources

Resources, such as fossil

fuels, that can’t be restored

within a human time frame.

pollutant A substance that

harms the health, activities,

or survival of a population.

renewable resources

Resources that can be

replenished.

What is an ecological footprint?

• An ecological footprint is a measure of a population’s impact
  on its environment—the total resources it consumes and the
  wastes it produces.


• Renewable resources can be replenished and so in theory
  may be available indefinitely. There are only finite amounts of
  nonrenewable resources.

taKe-Home messaGe

can be tapped indefinitely if they are replenished. On the

other hand, fossil fuels and minerals such as copper are

for all intents and purposes nonrenewable resources.

Earth’s crust contains

finite, limited amounts

of them. More may form

over many millions of

years, but not on a human

time scale. Therefore non­

renewable resources can

be depleted, leaving us to

our technological ingenu­

ity to find usable, cost­

effective replacements.

Pollution can result from human activities

Often, using a resource produces wastes that the user

must dispose of. All too often in technologically advanced

societies, wastes or chemical by­products of industry and

agriculture create pollution. A pollutant is a substance

that in some way harms the health, activities, or survival

of a population.

Natural events such as a volcanic eruption can release

pollutants, but today most pollution comes from human

activities. There are two basic sources

for pollution. A point source is a single

place or outlet, such as a leaky toxic

waste dump. A nonpoint source is not

tied to a particular location and so is

harder to pin down. Pesticide runoff

from farms and homes into a river or

bay is an example.

In the remainder of this chapter

we’ll consider the effects of human

activities on natural resources,

starting with the impact of indus­

try and fossil fuel use on the air

we breathe.

n Population growth and the unsustainable use of natural

resources are two major root causes of current and future

environmental problems.

Today we hear constantly about environmental challenges
facing humanity. Many of these problems are due directly
or indirectly to the growing human population and its
demand for natural resources.

Everyone has an ecological footprint

As societies strive to become more affluent, they replace
natural landscapes such as forests with cropland, factories,
and housing developments. Their citizens also want the
conveniences of affluent life—cars, labor­saving appli­
ances, computers, cell phones, and other electronic gadgets,
to name a few. Having more money also allows people to
travel over long distances and to buy more food—often,
more meat and fish—sometimes from sources thousands
of miles away. The net result of these and other changes is
a growing ecological footprint—a shorthand term for the
total resources a population consumes and the resulting
wastes that are returned to the environment. Each of us has
a personal ecological footprint as well.
Ecological footprints vary widely. For example, in a year
the average consumer in the United States uses 100 times
the resources consumed by someone in the poorest regions
of Africa and Asia (Figure 25.5). The ecological footprints
of people in rapidly developing nations such as China and
India are growing at the same rapid pace.

Some resources are renewable but others are not

Overall, our planet’s resources fall into two categories.
Renewable resources, such as fresh water and forests,

Figure 25.5 Who has the largest ecological footprint? In Africa
the rural poor rely heavily on homegrown crops and typically
lack access to conveniences people in wealthier regions take for
granted. (Left: Adrian Arbib/Encyclopedia/Corbis; Right: Don Mason/Cusp/Corbis)

U.S. Department of Agriculture

25.3 ecological “Footprints” and environmental problems

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