Environmental Engineering Reference
In-Depth Information
sources the
tragedy of the commons.
It happens be-
cause each user reasons, “If I do not use this resource,
someone else will. The little bit I use or pollute is not
enough to matter, and such resources are renewable.”
With only a few users, this logic works. Eventu-
ally, however, the cumulative effect of many people
trying to exploit a free-access resource exhausts or ru-
ins it. Then no one can benefit from it—and that is the
tragedy.
One solution is to
use free-access resources at rates
well below their estimated sustainable yields
by reducing
population, regulating access to the resources, or both.
Some communities have established rules and tradi-
tions to regulate access to common-property resources
such as ocean fisheries, grazing lands, and forests.
Governments have also enacted laws and interna-
tional treaties to regulate access to commonly owned
resources such as forests, national parks, rangelands,
and fisheries in coastal waters.
Another solution is to
convert free-access resources to
private ownership.
The reasoning is that if you own some-
thing, you are more likely to protect your investment.
That sounds good, but private ownership is not al-
ways the answer. Private owners do not always protect
natural resources they own when this goal conflicts
with protecting their financial capital or increasing
their profits. For example, some private forest owners
can make more money by clear-cutting timber, selling
the degraded land, and investing their profits in other
timberlands or businesses. Also, this approach is not
practical for global common resources—such as the at-
mosphere, the open ocean, most wildlife species, and
migratory birds—that cannot be divided up and con-
verted to private property.
Science: Our Ecological Footprints
Supplying each person with resources and absorbing
the wastes from such resource use creates a large
ecological footprint or environmental impact.
The
per capita ecological footprint
is the amount of bi-
ologically productive land and water needed to supply
each person with the resources he or she uses and to
absorb the wastes from such resource use (Figure 1-7,
left). It is an estimate of the average environmental im-
pact of individuals in different countries and areas.
The numbers shown in Figure 1-7 are estimates and
should not be taken literally. But they can be used to
show relative differences in resource use and waste
production by countries and geographical areas. See
Figures 2 and 3 in Science Supplement 2 at the end of
this topic for maps of our ecological footprints for the
world and the United States.
Humanity's ecological footprint exceeds the earth's eco-
logical capacity to replenish its renewable resources and ab-
sorb waste by about 21% (Figure 1-7, right). If these esti-
mates are correct, we are drawing down renewable resources
21% faster than the earth can renew them.
In other words,
it will take the resources of 1.21 planet earths to sup-
port indefinitely our current production and consump-
tion of renewable resources!
The ecological footprint of most people in devel-
oped countries is large because of their huge con-
sumption of renewable resources. You can estimate
Per Capita Ecological Footprint
(Hectares per person)
1.5
Country
9.6
United States
Earth's
Ecological
Capacity
1.2
3.8
The Netherlands
0.8
India
0.9
0.6
Total Ecological Footprint
(Hectares)
Country
3 billion
hectares
0.3
United States
62 million hectares
The Netherlands
0
880 million
hectares
India
1960
1970
1980
1990
2000
2010
Ye a r
Figure 1-7
Natural capital use and degradation:
relative
per capita and total ecological footprints
of the
United States, the Netherlands, and India (left). The
per capita ecological footprint
is a measure of the bio-
logically productive areas of the earth required to produce the resources required per person and absorb or
break down the wastes produced by such resource use. By 2001, humanity's ecological footprint was about
21% higher than the earth's ecological capacity (right). (Data from World Wide Fund for Nature, UN Environ-
mental Programme, and Global Footprint Network)
