Environmental Engineering Reference
In-Depth Information
the highly coupled nature of these hybrid human/natural systems makes
their degree of complexity quite challenging.
It is not that the co-dependence of natural and human systems is new
learning. Familiar examples include the numerous impacts of humans on
biota, through direct predation and indirectly through the introduction of
new species to indigenous habitats, which has been going on for cen-
turies.
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In fact, the distinction between a “human” system and a “natural”
one is itself somewhat artificial in many cases. Economic systems are gen-
erally considered human, and estuarine systems natural, for example,
although each is inevitably a complex mixture of both.What is different is
the striking discontinuity between the relatively minor and localized
impacts that predominated before the Industrial Revolution and the
global, systemic impacts of human activity that now characterize the inter-
relationships between human systems and fundamental biological, physical,
and chemical systems.
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In general, these effects have been unintended,
arising as the sum of human activities, grown to scales unprecedented for
any species in the history of the globe. Myriads of economic and engi-
neering decisions, evaluated and taken as if independent, are in reality
tightly coupled to each other and to underlying natural systems. Each
action in this process may, indeed, be planned, but the comprehensive, sys-
temic impacts, which are just becoming apparent, are neither planned nor
foreseen.
Consider one specific example, global climate change. Perturbations of
the carbon cycle arise from virtually all aspects of human economic
behavior, from subsistence farming to manufacturing to use of fossil fuels
to supply energy.An industrial ecology view of these perturbations reveals
a system that is highly complex but which may be managed if the prin-
ciples discussed above are kept in mind. Indeed, numerous options for
“geoengineering” responses to global climate change forcing have already
been identified,
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including direct ocean disposal of CO
2
, ocean fertiliza-
tion with phosphate, ocean fertilization with iron, reforestation, solar
shields increasing the planet's albedo, stratospheric SO
2
creation, injection
of inert dust into the stratosphere, and injection of SO
2
into the tropo-
sphere. Such options can be evaluated in light of the principles of indus-
trial ecology as well as on the basis of historic experience with complex
engineering projects (especially those involving systems engineering).
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As the following examples show, this background can be used to review
