Environmental Engineering Reference
In-Depth Information
consumer education, use of water-saving appliances and higher residential
densities.
Set against these improvements, however, the
State of the Environment
report listed the high per capita greenhouse gas emissions; increasing land
surface temperatures; loss of coastal habitat through the encroachment of
human settlements; pressures on our coral reefs from the downstream
effects of land use; large nutrient loads of nitrogen and phosphorus being
discharged to coastal and estuarine waters; the net loss of vegetative cover
from broadacre clearing; turbidity in waterways from soil erosion; large
areas of acidic soils; continuing deterioration of the health of surface and
groundwaters; an overall increase in water use and extraction for irrigation;
increasing algal blooms in waterways; persistence of the key threats to biodi-
versity such as salinity, land-clearing and exotic invasive species; consump-
tion outpacing population growth in electricity generation and transport
usage; and environmental noise and its effects on residents is increasing
from high residential densities and volume of traffic.
Australia currently has 5.1 per cent of the world's land area but only 0.3
per cent of its human population, largely because 70 per cent of the conti-
nent is arid. Even with one of the lowest population densities in the world,
our environment is being significantly degraded by human activity.
Water is perhaps our most precious resource. Australia is the driest
inhabited continent, characterised by variable climatic conditions and high
levels of evaporation. There is relatively little run-off, so Australian rivers
have low and variable flows and carry high levels of nutrient and sediment as
a consequence of agricultural land use in the catchment areas (ABS 2003).
Salinity and algal blooms also threaten Australian rivers and wetlands.
Meanwhile, Australia's unique biodiversity is threatened by a number of
other factors, the major one being clearance of native vegetation. Since Euro-
pean settlement, around 100 million hectares have been cleared, mostly for
agriculture. Over half a million hectares of native vegetation were cleared in
2000, a rate exceeded by only four other countries. Clearing of native vegeta-
tion not only destroys plants and habitats for animals, it helps invasive
species to spread which then compete with native wildlife. These include
foxes, cats, rabbits, goats and dieback fungus.
Australian soils are old, shallow and susceptible to degradation. Dryland
salinity, caused by rising watertables bringing salts to the surface, is affecting
20 000 farms across two million hectares, much of it in the Western Australian
