Australia is about the size of the United States, has about twenty million people, and is almost certainly already overpopulated, according to Jared Diamond. Despite the tiny population, almost all of whom are concentrated in a few large cities, serious and potentially catastrophic environmental degradation threatens on many fronts. The litany is familiar: Deforestation, soil erosion and salinization, desertification by overgrazing, exhaustion of critical resources.
How could such a large and lightly populated continent be so endangered? Its environment is exceptionally fragile, and many years of systematic mismanagement of resources have taken their toll. Australia has the least biological productivity of any continent, due to a double geological and climatic whammy. The rock in Australia is the World's oldest, with only minimal soil renewing glaciation or volcanism having taken place any time recently. Its rainfall is both sparse and erratic, depending heavily on the El Nino Southern Oscillation. In addition, it may well prove to be vulnerable to the climate changes due to global warming, which are likely to make it even dryer.
The good news, says Diamond, is that the population has awakened to the problem, and is pushing the governments, who are still largely in the thrall of special interests, for ameliorative action. If that fails, Oz could be the first first world country to see a sharp decline in its standard of living due to environmental problems.