Environmental Engineering Reference
In-Depth Information
became unsustainable, for instance, when populations grew too large as on
Easter Island, or irrigated lands were affected by salinisation and became
unproductive as in Sumeria, and civilisations duly collapsed.
With the new technologies of the Industrial Revolution 250 years ago,
however, a new carrying capacity was established. Food supplies increased
dramatically and global population 'exploded', increasing over tenfold in the
ensuing two and a half centuries, from 600 million to over six billion. This was
also aided by better medical care that meant lower death rates from disease. In
Australia, numbers grew from under half a million in c.1750 - all of whom
were Aboriginal hunter-gatherers - to 20 million in late 2003. While Australia's
population density is 'only' 2.5 people per square kilometre, most of the conti-
nent is arid or semi-arid and only 6 per cent is arable (Stanton 2003).
The global population continues to grow by 72.5 million a year (IPC
2004). Even with lower than replacement fertility rates in most industrial-
ised countries, populations continue to grow owing to the demographic lag-
time associated with the life spans of overlapping multiple generations. In
Australia, fertility rates have been of the order of 1.7 children per woman for
a number of years, yet natural increase (births minus deaths) remains well
over 100 000 annually (ABS 2004). This is falling slowly, but on current
trends will remain positive for another 30 to 40 years even without immigra-
tion. Despite this, net migration (immigration minus emigration) remains
high and is expected to even exceed the 131 000 annually that it reached in
2002-03. By mid-century, on current trends, Australia's population will be
around 27 million.
However, in the developing world, population numbers continue to
explode. Almost all of the growth in the coming half-century - over two
billion people - will occur in non-industrialised, poorer cities. Given that
over 800 million people are already chronically malnourished, that 1.1
billion people lack clean water and over 2.4 billion proper sanitation, this
further growth is potentially catastrophic (Postel 2004).
A study by Mathis Wackernagel and his team, published by the US
National Academy of Sciences, found that the world passed its regenerative
and absorptive capacity back in 1979 and with each subsequent year the
deficit is increased by 1 per cent (Wackernagel
et al.
2002). This means that
in 2004 we are 25 per cent over the limit - we are satisfying our excessive
demands by consuming the Earth's natural assets. We are now consuming
