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In
1987, the World Commission on Environment and Development
coined the term "sustainable development," which it defined
as "meeting the needs of the present without compromising
the ability of future generations to meet their own needs."
Since then, there have been many efforts to explain what
is meant by sustainable development, in particular closed-loop
ecosystems.
To an engineer, a sustainable system is one which is in
equilibrium or changing at a tolerably slow rate. In the
food chain, for example, plants are fed by sunlight, moisture
and nutrients, and then become food themselves for insects
and herbivores, which in turn act as food for larger animals.
The waste from these animals replenishes the soil, which
nourishes plants, and the cycle begins again.
If humans are to achieve sustainable development, we will
need to develop processes analogous to these natural closed-loop
cycles. Historically, humans have made a significant environmental
impact in their interaction with the natural world, causing
damage to the environment in two primary ways: by over-consuming
resources; and second, by destroying our environment through
pollution.
A pre-agricultural human required the earth to supply
a bit under 2,600 kcal of energy a day, about the same
as a common dolphin required, whereas a typical human
in the U.S. today requires the equivalent of a sperm whale's
supply, over 202,700 kcal per day. A common dolphin still
requires less than 2,600 kcal per day. Per year, humans
consume more fossil fuels than nature produces in one
million years. Under the traditional paradigm of economic
growth and development, increased consumption is a sign
of progress. Under a sustainable development paradigm,
however, such a disproportionate increase as we are experiencing
is a sign of ineptness that guarantees we will exhaust
the earth's resources.
Examples of pollution and its destruction abound, from
Chernobyl to the Exxon Valdez oil spill to the dense blanket
of pollution, dubbed the "Asian Brown Cloud," hovering
over South Asia, which scientists warn could kill millions
of people in the region, and which poses a global threat.
Major problems caused by pollution include stratospheric
ozone depletion, global warming, acid rain, unsafe drinking
water, hazardous/solid waste disposal, loss of plant and
animal species, and human health and well-being.
Although society has more recently begun to consider its
impact on the environment, environmental protection has
usually taken the form of end-of-pipe solutions that often
required considerable money and natural resources. As
a result, industry has been able to argue successfully
that these practices could compromise its profitability.
Ultimately, economic robustness and environmental sustainability
are inextricably intertwined. Environmental impact can
be defined as the product of three factors, as expressed
in the following equation:
| |
|
GDP |
|
environmental
impact |
| Environmental
impact |
=
population X |
-------- |
X |
------------------ |
| |
|
Person |
|
unit
of per capita GDP |
GDP represents the gross domestic product of a society,
and GDP per capita is a measure of consumption. The third
factor represents the amount of environmental impact per
amount spent on the item that causes the impact.
Clearly, reducing the impact on the environment, i.e.,
alleviating or offsetting damage to the environment, can
only occur if at least one of the three factors decreases.
The world's population has been swiftly rising for over
150 years, and is expected
to increase for another 25 to 50 years. Consumption
varies dramatically across the globe; for example, a person
living in the United States consumes roughly 30 times
as much as a person living in India. As countries continue
to develop, it is likely that global consumption will
rise, as GDP/person increases with improved standards
of living. Thus, the factor that can be decreased most
readily is the third one. Effective use of technology
can greatly affect the impact per capita on the environment;
thus, engineers have a significant role to play in reducing
environmental impact.
Sustainable development regards the human relationship
to nature as subject to usufructuary constraint, which
means that we have the right of limited use and enjoyment
of our natural world, but do not have the right to damage
it indiscriminately. The most effective way to abide by
this constraint is prevention - i.e., preventing non-sustainable
damage before it occurs, rather than trying to mitigate
it.
Sustainable development also shifts attention to pre-production
design and to the consumption of resources and disposal
of used materials. Waste treatment is replaced by pollution
prevention, with specific goals, such as the reduction
or elimination of hazardous materials.
The beauty of sustainability development is that it offers
a win-win situation, since sustainable practices carried
out by industry also improve its bottom line by saving
energy and reducing materials and waste. As a practical
matter, sustainable development will occur only if industry
recognizes that sustainable development is also economically
advantageous. A major challenge facing the movement for
sustainable development, then, is to persuade industry
and the governments that regulate industry that this is
the case.
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