Environmental Engineering Reference
In-Depth Information
The question whether our world has limits which may at some point constrain
human growth or human behaviour is not a recent question. Many people are aware
of the calculations of Robert Malthus in 1798; he observed that human population
was starting to grow at an exponential rate whereas food production tended to grow
at a linear pace, so that population would encounter a limit at some point in the fu-
ture on food supply. Of course those projections were too simplistic at the time since
they failed to foresee the dramatic increase in agricultural productivity and in the
areas of land devoted to agriculture which have, up to now, allowed food produc-
tion to keep pace. Nevertheless, even now around 1 billion people remain short of
food and concerns remain whether food supply can be increased to accommodate
the growing global population as it exceeds 7 billion. We have also had to sacrifice
large parts of the earth's biological systems and biodiversity, as large tracts of forest
are converted from their natural state to the agricultural monocultures required to
provide the food needed for increasing populations.
Food is one of the most basic of human needs, and may have been the first 'limit'
to be widely discussed but, as population and economies grew during the twentieth
century, other types of limits started to appear. The ability of local environments to
absorb the wastes produced by local populations became overwhelmed giving rise
to dead and putrid rivers, smogs, local poisonings by toxic chemicals, culminating
in the 1970s and 1980s by the discovery that man-made chemicals (whether they
be DDT, PCBs or chlorofluorocarbons) were indeed capable of spreading across
the whole planet and exceeding the limits of the global environment to absorb or
degrade them. The annual increase in atmospheric concentrations of carbon dioxide
and other greenhouse gases also shows that the environment's limit for coping with
human emissions of greenhouse gases has been exceeded by a large margin. Recent
work is pointing to a range of critical limits which may be fundamental to support-
ing human society; Rockstrom et al. (
2009
) list 9 critical limits which define what
they call “a safe operating space for humanity”- climate change, chemical pollution,
ocean acidification, stratospheric ozone depletion, atmospheric aerosols, biodiver-
sity loss, land use change, nitrogen and phosphorus cycles, and global freshwater
use. Of these, three (climate, biodiversity and nitrogen) have already substantially
been exceeded and others (ocean acidification and freshwater) are close to the 'safe
operating space' boundary. Thus now there is little question whether there are lim-
its, the question is more how society will respond to such limits and to what extent
the future of humankind will be determined by them.
Limits were also recognized in the report which brought the concept of sustain-
able development onto the world stage in 1987, and led to the adoption of the prin-
ciple of sustainable development in the Rio Earth summit in 1992. As stated in the
Brundtland report (WCED
1987
) sustainable development is not just about “
devel-
opment that meets the needs of the present without compromising the ability of fu-
ture generations to meet their own needs
” but also has to recognize the “
limitations
imposed by the state of technology and social organization on the environment's
ability to meet present and future needs
”. Global warming or climate change is an
example of the results of our economic activities exceeding such limits. Human
activities, at the same time, lead to the depletion of energy and a range of natural
