Biodiversity implications of water management in the Great Artesian Basin.

The Great Artesian Basin (GAB) underlies a vast, mainly arid, region where most of the indigenous biota are not dependent upon surface water. In contrast, an important minority is dependent on refuges such as mound springs and their associated wetlands. In some parts of the GAB, such as western New South Wales, many springs have either ceased to flow, or are now barely detectable, because the proliferation of artesian waterbores has reduced groundwater pressures. Because of the rarity of species endemic to mound springs, and the damage they have suffered since pastoral settlement, emphasis should be directed towards conservation and possible rejuvenation of these ecosystems. Provision of artificial sources of water allows more widespread grazing by livestock, larger native and feral herbivores, thereby posing threats to native plants and animals that do not use the water. Because of the proliferation of artificial waters and the grazing they allow, terrestrial grazing-sensitive species now appear to be confined to tiny patches in the landscape. Some nature reserves within the GAB retain numerous artificial sources of water. Most of these should be closed over time to reduce negative impacts on grazing-sensitive plants and animals, especially where these species are inadequately protected elsewhere. In those regions where the ratio of artificial to natural waters is still low, consideration should be given to balancing provision of water for livestock with conservation of biological diversity, by maintaining a patchwork of areas remote from water. In regions where the density of artificial waters is high, conservation of biodiversity on freehold and leasehold lands might be enhanced with a mix of approaches accommodating the needs of the biota and the aspirations of landholders, tailored according to land type and condition.