Environmental Engineering Reference
In-Depth Information
surface to provide its material and energy needs and to absorb its wastes. For
large cities such as London this 'footprint', or ecological overshoot factor, is
around 100-200 times the size of the city itself. For example, at a national
level, it is estimated that the Dutch population requires an area of Earth's
surface approximately 15-20 times greater than the area of the Netherlands.
At the personal level, each Australian currently requires, on average, a land-
surface area of eight hectares to supply their food, energy and other materi-
als and to absorb their wastes. Unlike the Netherlands, our population size is
- at the moment - approximately in balance with the amount of biologically
productive land surface in Australia (although we are clearly mismanaging
freshwater supplies and losing species of animals and plants). Globally, how-
ever, if resources were shared both equally and sustainably, the available area
per person for a population of 6.4 billion would be around two hectares.
That is, we in Australia currently use much more than our fair share of
Earth's resources.
Some very recent research has attempted to quantify the time-trend over
the past four decades in humankind's ecological overshoot. Globally, it looks
as if we have been operating 'in the red' for the past 20 years or so. Currently
we are extracting from the biosphere, annually, a total of natural 'goods and
services' that is about 25-30 per cent higher than can be provided sustaina-
bly (Wackernagel
2002). In other words, we are now into the realm of
ecological deficit budgeting, and, with current technologies and social prior-
ities, we can only balance the topics annually by continuing to deplete
natural capital. This necessarily means that we are transmitting to future
generations a partially depleted and less life-supporting biosphere. This has
wide-ranging consequences for the future prospects of population health.
et al.
Global climate change and health
The best-known example of these modern global environmental changes is
climate change. There has been a clear trend in global warming over the past
three decades, and climatologists are now confident that most of this
increase has been due to human influence on the composition of the lower
atmosphere. Further, it has become apparent that, in recent decades, many
non-human physical and biological systems have undergone alterations that
are reasonably attributable to climate change.
The human species, via social organisation and cultural practice, is much
better buffered against environmental stressors than are all other plant and
