A major contributor to air pollution in Australian cities is
the motor vehicle, the number of which increases with rising populations.
Motor vehicles are responsible for 80 to 90 per cent of carbon
monoxide and lead emissions, and 50 to 80 per cent of hydrocarbon
and nitrous oxide emissions. Although technological changes and
regulations have kept some emissions in check, ozone and nitrogen
dioxide have increased to unacceptable levels in the large cities.
Photochemical smog sometimes goes above national health guidelines
in areas of Sydney such as the south-west and around Melbourne.
It is because of concerns about air quality that the NSW Government
has decided to limit housing development in the south-west of
Sydney. However, since the pollutants flow there from elsewhere
in the city, this may be a rather limited solution.
Water pollution resulting from flows of domestic sewage and urban
run-off is also related to population levels (although it is also
a function of treatment and urban design). Sydney's Nepean&endash;Hawkesbury
river system is already under severe stress because of urban development.
Nutrient, bacteria and virus levels are high because of inflows
of sewage and agricultural run-off. Yet the NSW Government is
proposing to develop additional housing for thousands of families
within the catchment of this river system, adding to its load.
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Water supply is said to be another potential constraint on population
growth in many parts of Australia. For example, the population
issues committee estimates that new sources of water will have
to be found early next century if increases in population and
use of water per person in the Sydney area continue to grow as
they have been. This would probably mean a dam on the Shoalhaven
River, which would not only be expensive and energy intensive
because of the pumping that would be required, but would also
be environmentally undesirable, as would the alternative of raising
the level of the Warragamba Dam. Nevertheless, while water is
in relatively short supply in Australia, its use depends not only
on population levels but also on agricultural and industrial consumption
and how efficiently the water is collected, distributed and used.
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Disposing of the solid waste from large populations causes environmental
pressure in cities. Domestic solid waste generated by households
accounts for one-third to one-half of all solid waste generated
in large cities. This amount depends on the numbers of people
and the amount of rubbish they each generate. The population issues
committee estimates that almost half of the growth in solid waste
is due to population growth, and just over half is due to increased
resource use per person (1992, p. 60). Increased recycling and
reuse and less throw-away packaging could also affect the relationship
between numbers of people and the garbage generated.
Each year, Sydney and Melbourne residents generate hundreds of
thousands of tonnes of paper and cardboard, glass, plastic, and
other wastes. Solid waste is generally buried in the ground, which
has a number of adverse environmental consequences. Resources
are wasted, land is used up, smells and visual nuisances are created,
and groundwater may be polluted. The waste often has to be transported
long distances to be buried. If it is incinerated, the resources
are still wasted and toxic air emissions are generated.
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Population increase also puts pressure on existing housing, raising
prices and forcing some people out of the city because they cannot
afford to live there. Some people respond to rising prices by
moving to the outer fringes of the city, promoting urban sprawl.
Generally, these fringe areas are poorly served by public transport
and other community facilities, so urban sprawl involves additional
motor vehicle travel to work and to community facilities. It can
also mean that prime agricultural land is turned over to residential
The NPC's population issues committee concludes that, although
there is still far more to learn about the links between population
levels and environmental impacts, 'there is some significant evidence
of negative influence of urban population growth on urban ecological
integrity' (p. 60). Some people move out of the cities because
they find them congested and unpleasant. Often, they move to the
coastal regions where they find a beautiful natural environment.
However, as more people move to these areas, species preservation
can be threatened and the natural environment damaged.
Source: Sharon Beder, The Nature of Sustainable Development
2nd ed. Scribe, Newham, 1996, pp. 161-3.
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