The Cooper subregion has a high diversity of ecological communities and species as a consequence of the interactions between its large area, its diversity of surface geological types and soils, a gradient of rainfall seasonality, and the importance of landscape form driving water and soil redistribution in semi-arid environments of inland Australia. This diversity is expressed through the presence of 14 subregions of the Interim Biogeographic Regionalisation for Australia (IBRA; Department of the Environment, 2014a; SEWPaC, Dataset 1) and 27 major vegetation subgroups of the National Vegetation Information System (NVIS; Department of the Environment, 2014b; Australian Government Department of the Environment, Dataset 3). Pastoral grazing is by far the most frequent land use (>80%) and conservation reserves occupy around 9%.
The most common terrestrial vegetation NVIS subgroups are (i) Saltbush and/or bluebush shrublands, (ii) Mitchell grass (Astrebla) tussock grasslands, (iii) Hummock grasslands, and (iv) Mulga (Acacia aneura) open woodlands and shrublands. Other vegetation subgroups occur with lower frequency and form a mosaic that gradually changes from north-east to south-west across the subregion. However, there has been a lack of cross-border harmonisation of NVIS vegetation subgroups between states, meaning that it is difficult to interpret vegetation patterns for the subregion as a whole. The area has been subject to almost no clearance of vegetation. Pasture components are reported to have stable condition.
Wetlands listed formally in A directory of important wetlands in Australia (DIWA; Department of the Environment, 2014c; Australian Government Department of the Environment, Dataset 9) occupy 12.8% of the area of the Cooper subregion, and riverine floodplains that are also potentially water dependent occupy 12.2% of the area.
As rivers and lakes are all intermittent, the durations of flow and non-flow periods, as well as the depth of water, together are important determinants of the number of species locally per unit area and degree of species sharing amongst lakes, rivers and residual waterholes. The ecology of rock holes (shallow depressions that collect local rainwater) and outcrop springs (springs of water that has percolated through rock layers in the immediately surrounding area) is poorly studied, as is the ecology of the species that occur within aquifers below ground level (stygobiota). Discharge springs (springs of water that had percolated through rock layers over long distances and from which water emanates under pressure) are better studied, and numerous locally endemic species have been identified. While there are no discharge springs within the Cooper subregion, there are such springs in the immediately adjacent parts of the Great Artesian Basin which may be hydrologically connected to the Cooper subregion. The ecology of both discharge springs and stygobiota is understood to depend on relatively stable water regimes, compared with the highly intermittent character of other aquatic habitats in the region. Discharge springs are highly sensitive to changes in groundwater; over the last century, water drawdown for pastoralism has resulted in significant degradation such that as few as one-third of discharge springs identified in the western Great Artesian Basin in 1900 are still active and leading to the bore-capping programme. There are no data on impacts of agricultural drawdown on stygobiota. Riverbanks and waterholes are generally assessed to be in better condition.
In the Cooper subregion, 18 species are listed nationally under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999, of which only one species is water dependent beyond incident rainfall. While the community of native species dependent on natural discharge of groundwater from the Great Artesian Basin is also EPBC-listed, it is not found directly within the subregion. A further 45 species are listed under Queensland’s Nature Conservation Act 1992, 48 species under NSW’s Threatened Species Conservation Act 1995, and 82 species under SA’s National Parks and Wildlife Act 1972.
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- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
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