The deserts in the Australasian realm (Figure 4.2) comprise 10 flat, lowland ecoregions (Carnarvon xeric shrublands, Central Ranges xeric scrub, Gibson Desert, Great Sandy-Tanami Desert, Great Victoria Desert, Nullarbor Plains xeric shrublands, Pilbara shrublands, Simpson Desert, Tirari-Stuart Desert, Western Australian Mulga shrublands), covering in total some 3.6 million square kilometres, of which some 9 per cent has some level of environmental protection. Hardly inhabited at all, their mean population density is less than 1 person per square kilometre. These deserts show, by far, the lowest human footprint of the global biome.

All the arid ecoregions identified in Australia receive only sporadic rain and carry sparse vegetation but each one presents its own peculiarities. The Gibson Desert, the "great undulating desert of gravel", is an area of red gravel soils with mulga (Acacia aneura) accompanied by other droughtresistant shrubs and hardy spinifex (Triodia) grass. The Central Ranges xeric scrub has low myall and desert oak woodlands growing over spinifex on the sand plains, whereas throughout the ranges, a profusion of endemic ferns, reeds, and rushes grows in gorges where there is ample water. The Great Sandy-Tanami Desert is an extensive area of reddish sand plains out of which rises the great Uluru (Ayers Rock); the plains are covered by clumps of spinifex and scattered saltbush (Atriplex spp.) with sparse, spiny acacias and tall desert oaks (Allocasuarina decaisneana). The vegetation in the Great Victoria Desert is restricted to the hardiest of species, such as spinifex. The dunes and sand plains of the Simpson Desert carry sparse shrubs and spinifex with cane grass (Eragrostis australasica) on the deep sands along the crests of dunes, and coolibah (Eucalyptus sp.) snaking across the northeastern corner. The Tirari-Stuart Desert is characterized by vast sand dunes that harbour an abundant and diverse fauna, an array of unique creatures that have adapted to the high temperatures and soil aridity (marsupials, lizards, frogs and even small parrots). Important fossil deposits have been discovered in the area. Over the Tirari-Stuart Desert sparse saltbush sustains sheep grazing, while its southern portion is woodland with native cypress, black oak, and eucalyptus. Both the Gibson and the Great Sandy-Tanami Deserts are extensive rangelands, mostly uninhabited but supporting important mining activities. Threats include overgrazing, and feral and exotic animals, in addition to the localized and sometimes severe disturbances caused by tourism and mining.