Vegetation in the region is mainly woody, including forests, woodlands, shrublands, and heathlands, but no grasslands. Predominant vegetation types are Eucalyptus woodlands, eucalyptus-dominated mallee shrublands, and kwongan shrublands and heathlands, which correspond to the chaparral, matorral, maquis, and fynbos shrublands found in other Mediterranean-type regions. The region has generally nutrient-poor sandy or lateritic soils, which has encouraged rich speciation of plants adapted to specific ecological niches. The region hosts a great diversity of endemic species, notably among the protea family. Southwest Australia is recognized as a floristic province.
The transitional Coolgardie, Hampton, and Yalgoo regions are generally drier than the rest of the Southwest. They considered part of Southwest Australia by the WWF, but are considered part of the Central Australian or Eremaean Region by the Western Australian Herbarium.
Freshwater
Southwest Australia has several permanent rivers and streams, including the Swan–Avon system, the Blackwood River, and other short rivers. The perennial rivers drain from the interior plateau and Darling Range across the coastal plain. Their flow is strongly seasonal, corresponding to the Southwest's wet winter–dry summer weather pattern. The perennial streams extend from east of Esperance on the south coast to the Arrowsmith River north of Perth, most often in areas with 700 mm or more of annual rainfall. Arid regions separate Southwest Australia's freshwater habitats from Australia's other year-round rivers. As with its terrestrial flora, Southwest Australia's Mediterranean climate and biogeographic isolation has given rise to a distinct freshwater ecoregion with many endemic species. There are fifteen freshwater fish species, including nine exclusively freshwater species, three estuarine species adapted to brackish water, and three diadromous species that spend part of their life-cycle in the sea. The exclusively freshwater species are endemic to Southwest Australia, as are two estuarine species. The salamanderfish is the sole species in the endemic family Lepidogalaxiidae. Salamanderfish can aestivate during the summer months, an adapation to the region's dry summers. Other endemic species are the nightfish, western mud minnow, black-stripe minnow, Balston’s pygmy perch, western pygmy perch, and western galaxias. Southwest Australian varieties of the diadromous common galaxias and spotted galaxias have adapted so they can live their life-cycle and reproduce in fresh water. The southwestern snake-necked turtle and western swamp turtle are aquatic species endemic to Southwest Australia.
Conservation
The context of the region in European colonist histories of the region is of limited understanding knowledge of the country as opposed to the indigenous understanding.
