Threats to Australia's Freshwater Biodiversity
Rivers, lakes and wetlands contain only a fraction of the world’s water and cover less than 1% of the Earth’s surface, yet they support about 40% of the planet’s fish diversity and a quarter of the known vertebrate species. However, extinction rates of freshwater animals are the highest of any other ecosystem, and freshwater ecosystems are already regarded as the most threatened on the planet. Further marked declines in freshwater biodiversity are predicted as a consequence of climate change and an expanding global human population. Projected changes in the Australian climate are likely to directly affect freshwater biodiversity, for example, through losses of coastal freshwater habitats from rising sea level and from increased water temperatures. Some freshwater species have a narrow range of temperature tolerance and those with highly restricted distributions (e.g. mountain crayfish and frogs) are at obvious risk. The direct impacts of increased variability and severity of extreme hydrological events (especially droughts) are likely to be far more pervasive. These climate-driven impacts will be compounded by growing human demands for water. Under mounting public pressure, governments have recently declared plans to drought proof cities and to either divert water south or move farmers north to meet agricultural needs. As in other parts of the world, it is the construction of dams and alteration to flow regimes associated with such developments that will have a far greater impact on freshwater biodiversity than climate change per se. Australia has a unique freshwater fauna and many freshwater ecosystems with outstanding natural assets and values. We must ensure that the current panic to meet our demands for water does not exacerbate the effects of a changing climate and lead to far greater declines in biodiversity.