The human ecology of climate change - Climate Change: Biological and Human Aspects - page 364

The human ecology of climate change

7

Given that climate change has been part of, and has helped shape, the biosphere's
development, it should not have been surprising that climate change affected human
evolution and humanity's historical affairs (see Chapter 5), or that it will do so in
the future. That humanity itself has affected the climate - modern technological
civilisation significantly so - all the more demonstrates the interconnections between
climate and our species. If we are to begin to assess the future of this relationship it
is necessary to understand the relevant fundamentals of human ecology (the way our
species as a population develops and its relations with other species). This includes
population demographics (our numbers influence the amount of biomass of, and
hence impact on, the species to which we relate), energy supply (which relates to
carbon cycle short-circuiting), health (mainly with regard to those species that prey
on us) and food supply (those species that we harvest). Finally, given all of this, what
are the prospects for limiting or ameliorating our short-circuiting of the biosphere's
carbon cycle?

7.1 Population(past,presentandfuture)andits
environmentalimpact

7.1.1 Populationandenvironmentalimpact

Generally, if one person has an environmental impact of some arbitrary quantification,
x , then it is not unreasonable to suppose that two people will have an impact of 2 x , three
people an impact of 3 x , etc; in other words, that environmental impact is proportional
to population and so may be represented in equation form.
One of the first environmental-impact equations widely considered, where impact
is proportional to population, was formulated by Paul Ehrlich and John Holdren
(1971). It was expressed as:

I = PA T

where I is the impact on the environment resulting from consumption, P is the
population, A is the consumption per capita (affluence) and T is a technology or, as it
has more recently sometimes been known, an inefficiency (inverse efficiency of use)
factor.
Today, environmental impact is considered in a more complex and multifactorial
way. Most often impact is not considered in terms of arising from a human population,

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