is a large area of relatively unspoilt grassland used for grazing cattle. Some damage results from intensive cattle ranching leading to overgrazing and disrupting the traditional Aboriginal fire regimes in which the grasslands are systematically burnt and allowed to regenerate. Woodlands next to rivers and other water sources were severely altered when ranching began, causing siltation along the Ord River and destroying important habitat of the white-browed robin (Poecilodryas superciliosa) and the purple-crowned fairywren. Habitats have also been damaged by introduced species of plants such as bellyache bush (Jatropha gossypifolia), and castor oil plant (Ricinus communis). There are some protected areas, mainly other types of habitat rather than grazing land. Areas such as the caves of Gregory National Park are still being researched by botanists and zoologists. See also Geography of Australia References Further reading https://web.archive.org/web/20100506065506/http://www.anra.gov.au/topics/rangelands/overview/wa/ibra-ovp.html Thackway, R and I D Cresswell (1995) An interim biogeographic regionalisation for Australia : a framework for setting priorities in the National Reserves System Cooperative Program Version 4.0 Canberra : Australian Nature Conservation Agency, Reserve Systems Unit, 1995. Biogeography of Western Australia IBRA regions Kimberley (Western Australia) Plains of Australia Tropical and subtropical grasslands, savannas, and shrublands Biogeography of the Northern Territory