The Simpson Desert is a large area of dry, red sandy plain and dunes in the Northern Territory, South Australia and Queensland in central Australia. It is the fourth-largest Australian desert, with an area of 176,500 km2 (68,100 sq mi).
The desert is underlain by the Great Artesian Basin, one of the largest inland drainage areas in the world. Water from the basin rises to the surface at numerous natural springs, including Dalhousie Springs, and at bores drilled along stock routes, or during petroleum exploration. As a result of exploitation by such bores, the flow of water to springs has been steadily decreasing in recent years. It is also part of the Lake Eyre basin.
The Simpson Desert is an erg that contains the world's longest parallel sand dunes. These north-south oriented dunes are static, held in position by vegetation. They vary in height from 3 m (9.8 ft) in the west to around 30 m (98 ft) on the eastern side. The largest dune, Nappanerica or Big Red, is 40 m (130 ft) in height.
The Simpson Desert is also a large part of the World Wildlife Fund ecoregion of the same name, which consists of the Channel Country and the Simpson Strzelecki Dunefields bioregions of the Interim Biogeographic Regionalisation for Australia (IBRA).
The flora of the Simpson Desert ecoregion is limited to drought-resistant shrubs and grasses, especially Zygochloa paradoxa grass that holds the dunes together and the spinifex and other tough grasses of side slopes and sandy desert floor between the dunes. The Channel Country section of the ecoregion lies to the northeast of the desert proper around the towns of Bedourie and Windorah in Queensland, and consists of low hills covered with Mitchell grass cut through with rivers lined with coolabah trees. The ecoregion also includes areas of rocky upland and seasonally wet clay and salt pans, particularly Lake Eyre, the centre of one of the largest inland drainage systems in the world, including the Georgina and Diamantina Rivers.
Wildlife adapted to this hot, dry environment and seasonal flooding includes the water-holding frog (Litoria platycephala) and a number of reptiles that inhabit the desert grasses. Endemic mammals of the desert include the kowari (Dasycercus byrnei), while birds include the grey grasswren (Amytornis barbatus) and Eyrean grasswren (Amytornis goyderi). Lake Eyre and the other seasonal wetlands are important habitats for fish and birds, especially as a breeding ground for waterbirds, while the rivers are home to birds, bats, and frogs. The seasonal wetlands of the ecoregion include Lake Eyre and the Coongie Lakes, as well as the swamps that emerge when Cooper Creek, Strzelecki Creek, and the Diamantina River are in flood. The birds that use these wetlands include the freckled duck (Stictonetta naevosa), musk duck (Biziura lobata), silver gull (Larus novaehollandiae), Australian pelican (Pelecanus conspicillatus), great egret (Ardea alba), glossy ibis (Plegadis falcinellus), and banded stilt (Cladorhynchus leucocephalus). Also, the mound springs of the Great Artesian Basin are important habitat for a number of plants, fish, snails, and other invertebrates.
Native vegetation is largely intact as the desert is uninhabitable, so habitats are not threatened by agriculture, but are damaged by introduced species, particularly rabbits and feral camels. The only human activity in the desert proper has been the construction of the gas pipelines, while the country on its fringes has been used for cattle grazing and contains towns such as Innamincka. Mound springs and other waterholes are vulnerable to overuse and damage. Protected areas of the ecoregion include the Simpson Desert, Goneaway, Lochern, Bladensburg, Witjira and Kati Thanda-Lake Eyre National Parks as well as the Innamincka Regional Reserve, and the Munga-Thirri–Simpson Desert National Park.
Ethabuka Reserve is a nature reserve in the north of the desert owned and managed by Bush Heritage Australia.