Environmental Engineering Reference
In-Depth Information
Similarly, the construction of buses and trains entails considerable use of
materials and energy. Until they can be run purely on renewable energy
(such as electricity from wind power) they too will contribute to greenhouse
gas emissions. Even bicycles, powered ultimately by food consumed by
humans, require materials and energy to manufacture.
So while all efficiency initiatives in the area of transport and urban
design are to be applauded, they must go hand in hand with a cap on popu-
lation growth if sustainability is to be achieved.
Conclusion
Twenty-five years ago, in 1979, the world passed its regenerative and absorp-
tive capacity, that is, exceeded its human carrying capacity. The cause was a
combination of an explosion in human numbers and their economic activi-
ties. Focus in the sustainability debate has too often just been on economic
activities - reducing consumption, moving to a renewable energy economy
and so on - while the population aspects have been ignored. Numbers are
stabilising in the industrialised world. However, many nations in the devel-
oping world are still experiencing very high and absolutely unsustainable
rates of growth. In Australia, growth continues despite lower than replace-
ment fertility rates through a combination of natural increase and high net
overseas migration.
Population growth often negates efficiency measures. For instance, many
Australian cities are implementing ever more stringent water-efficiency
measures but continuing population growth offsets these. Energy-efficient
appliances are being promoted, quite rightly, but if the overall number of
consumers increases then little is gained with respect to sustainability.
A combination of resource scarcity, environmental decline and over-
population can lead to anarchy and other forms of conflict. Water shortages
- the result of global warming and too many people for the water available -
are looming as a major source of conflict in the 21st century.
The greatest challenge to sustainability is global climate change, a func-
tion of too many people and their activities. Unless greenhouse emissions
are reduced 70 per cent or more and the atmosphere stabilised, global
warming could wreak havoc on the Earth. Yet we must do this while lifting
an existing two billion out of poverty, and coping with another two billion or
more people in the next half century. Moving from a fossil fuel-based
economy to a renewable one based on solar power is essential, along with
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