Ecosystems and Conservation

Australia had been isolated from the rest of the world for millions of years until relatively recent human settlement. Some species are found over quite limited ranges of average climate. These two factors leave many of the region's ecosystems vulnerable to climate change and to invasion by exotic animal and plant species introduced by human activity. This vulnerability has been exacerbated by fragmentation of ecosystems through land-use changes.

Warming of 1 °C would threaten the survival of species currently living near the upper limit of their temperature range, notably in some Australian alpine regions where some species are already near these limits, as well as in the south-west of Western Australia. Other species that have restricted climatic niches and are unable to migrate because of fragmentation of the landscape, soil differences, or topography could become endangered or extinct. Other ecosystems that are particularly threatened by climate change include coral reefs and freshwater wetlands in the coastal zone and inland.

Australia has one of the greatest concentrations of coral reefs in the world. Rising sea level by itself may not be deleterious. However, the combination of sea level rise with other induced stresses-notably, increasing atmospheric carbon dioxide (which leads to a decrease in calcification rates of corals); increasing sea temperatures, leading to coral bleaching; possibly increased riverine outflow events causing low salinity and high pollution; and damage from tropical cyclones-may place much of this resource at risk.

Projections for coral bleaching suggest that serious bleaching events will become more frequent, decreasing the chance of recovery and leading to increasing death of corals. Major bleaching events in 1997-98 and 2002 may be forerunners, with warming trends combining with El Niño events to produce sea surface temperatures above bleaching thresholds.