|
|
Freshwater systems in arid Australia support species with amazing adaptations to some of the world’s most unpredictable patterns of water flow. This region has high numbers of endemic species, many of which have survived here for millions of years. When Australia split off from Antarctica 50 million years ago, its status changed. Instead of being part of the driest continent on Earth, it was now the second driest. Not much has changed since then, at least in terms of climate and rainfall. The Central Australian Freshwater ecoregion is located in the most arid part of Australia, receiving an average of only 5 inches (13 cm) of rain each year. Although it rains occasionally in central Australia, you can never be sure when. This unpredictable weather challenges farmers but doesn’t seem to bother many freshwater species. They've had millennia to adapt to the dry landscape and unpredictable availability of surface water.
This ecoregion is defined primarily by the Lake Eyre and Bulloo-Bancannia drainage basins, though it also overlays a portion of the Great Artesian Basin, one of the world’s largest artesian (underground) basins. The Great Artesian Basin lies beneath one-fifth of the continent. Around the artesian basin occur numerous mound springs such as Dalhousie Springs. These springs, some of which are as warm as 115°F (46°C), can be as old as a million years. The heat in central Australia quickly evaporates much of the rain that falls, so lakes like Eyre are intermittent, and when they are full, they are generally encircled by deposits of salt. These lakes are fed by the Diamantina and several other rivers only when occasional heavy rain causes them to flow. This ecoregion contains a large number of endemic fish, wetland-dependent plants, crustaceans, and snails. A fish called the desert gobi lives in small creeks and ponds associated with the Lake Eyre basin. Endemic fish of the Dalhousie Springs basin include the Dalhousie catfish, Dalhousie hardyhead, Dalhousie mogurnda, and Dalhousie gobi. Other endemics found at Dalhousie Springs include at least six snails, a blind crustacean, and possibly one crayfish and one frog species.
In this arid ecoregion, any water withdrawals or other changes that affect the flow of water pose serious threats to aquatic species. Exotic species, including Australian animals from outside this ecoregion, threaten native species by preying on them or by breeding with them and creating hybrids. Illegal fishing for local consumption and commercial trade is a serious problem. Overgrazing of surrounding lands by introduced rabbits and livestock has led to soil erosion and, as a result, pollution of these fragile aquatic ecosystems by sediment. Large populations of feral and domesticated grazing animals also pollute waters with their wastes. Future threats include proposed dams and water diversions, as do commercial fisheries.
|
