Great Sandy-Tanami Desert

• Category: Desert Biomes.
• Geographic Location: Australia.
• Summary: This vast desert ecoregion consists of three smaller deserts. It is known worldwide for the landform known as Uluru or Ayers Rock, a feature sacred to the Anangu Aborigines of this region.

The Great Sandy-Tanami Desert biome extends from Western Australia into the Northern Territory. It consists of three smaller desert regions: the Little Sandy Desert, located west of the Gibson Desert and east of the Great Northern Highway; the Great Sandy Desert, north of the Little Sandy in the northwest section of western Australia; and the Tanami Desert, a rocky, hilly desert in the Northern Territory. Together, the deserts stretch across roughly 490,000 square miles (1.26 million square kilometers).

All three deserts are ecologically significant. Rainfall throughout the area is low, though high by desert standards; even the driest regions have annual precipitation of about 10 inches (25 centimeters). The desert-defining aridity is preserved not so much by a dearth of precipitation, as by the extremely high evaporation rate due to the prevailing heat. Even winter low temperatures are in the high-70-degrees F (20-degrees C) range.

The Sandy deserts contain several large ergs, also called dune seas or sand seas—long, broad, flat areas of desert in which aeolian (windblown) sand covers a large part of the surface. These sands, important features of the desert ecosystem, are formed from aeolian processes that break down, erode, shape, and deposit rock and the resulting particles. These same processes help create desert varnish—a paper-thin coating of minerals (especially clays, manganese, and iron oxides) that forms on exposed rocks, sometimes combined with a microbial film of lichens and possibly microfauna, whose acidic excretions contribute to the ongoing breakdown of rocks into the salty soils of desert sand. The sands of both the Little and Great Sandy Deserts have a notable red hue.

Flora and Fauna

The dominant vegetation of the region is spinifex, an Australian desert grass of the Triodia genus (unrelated to grasses of the genus Spinifex). The grass has awl-shaped, pointed leaves that store water during dry periods. The leaf tips are sharp and high in silica, because of the soil in which the grasses grow, and have been known to injure people. Aborigines use spinifex to build shelters and fish traps, cook seedcakes, and prepare an adhesive used in making spears. Other plant species found here that have adapted well to the desert climate include: the Livistonia palm, native walnut (Owenia reticulata), and desert oak (Casuarina decaisneana). One endemic (found nowhere else on Earth) plant species is Wickham's grevillea (Grevillea wickhamii), a shrub.

Wildlife includes numerous species of lizards, such as the thorny devil (Moloch horridus), which is covered in uncalcified spines; the spines and ridges allow it to collect water from any part of its body, as when water condenses as dew in the night, as well as acting as a defense against predators. It moves oddly, rocking back and forth, conserving energy while searching for food, usually ants, in the spinifex sandplain. The devil can also suck water into its body from the surface of its skin, drinking in rainwater before it has a chance to run off.

Predators of the thorny devil include the goanna (genus Varanus), an Australian monitor lizard that grows to as much as 6 feet (2 meters) long, with sharp claws and teeth and strong jaws. The goanna principally preys on animals small enough to eat whole; when seen feeding on larger animals, it is nearly always scavenging, consuming carrion that it discovered already dead. The largest goanna species in Australia, the perentie (Varanus giganteus), is found in the Sandy deserts. The Pogona genus of lizards known as bearded dragons is also found here.

The deserts are also home to the bilby (Macrotis lagotis), marsupial carnivore mulgara (genus Dasycercus), marsupial mole (Notoryctes caurinus), rufous hare-wallaby (Lagorchestes hirsutus), red kangaroo (Macropus rufus), desert tree frog (Litoria rubella), sandy burrowing frog (Limnodynastes spenceri), desert spadefoot toad (Notaden nichollsi), feral camel (Camelus dromedarius and C. bactrianus, both introduced to Australia in the 19th century), and the dingo (Canis lupus dingo).

Many desert species are specially adapted to the region. The red kangaroo's gait, for example, is an energy-efficient way of traveling from food source to food source, and minimizes the amount of time the kangaroo's footpads are in contact with the hot daytime sand.

Significant endemic mammals in the Great Sandy-Tanami Desert include the long-tailed planigale (Planigale ingrami), the smallest of all marsupials and one of the smallest mammals at less than 2.5 inches (6 centimeters) long; the western chestnut mouse (Pseudomys nanus); and the delicate mouse (Pseudomys delicatulus). The Tanami, along with the rest of the region, is also home to the rare grey falcon (Falco hypoleucos), typically found in the Triodia grasslands and Acacia shrublands. The grey falcon is one of Australia's mystery birds, rarely seen.

Human Impact

While the Great Sandy-Tanami Desert biome remains largely intact, concerns over negative environmental impact stem from overgrazing in some areas, mining activities, tourist activities, and changes in native and endemic species due to intended or unintended introduction of foreign plant and animal species. Feral and invasive animals cause great damage to the ecosystems. The Australian Outback had an estimated 1 million feral camels in 2010. The animals eat more than 80 percent of available plant species, destroying ecosystems. The government's National Feral Camel Action Plan brought camel numbers down to an estimated 300,000, but the reduction is just one small step since experts predict that camels can double their population in just eight years. Camels are just one of many invasive species threatening the desert.

Also of concern are changes in weather caused by global warming and climate change. Heat waves, drought, and fires have ravaged the continent of Australia, including its deserts. Experts fear that the situation will worsen in the future. Fires have always been a natural part of Australia, however, human activities have caused more frequent fires, giving the environment little time to recover between fire occurrences.

Bibliography

Beard, John Stanley, and M. J. Webb. Vegetation Survey of Western Australia: Great Sandy Desert. Canberra: University of Western Australia Publishing, 1974.

Fishers, Rohan and Neil Burrows. "Professional Firefighters 'Astounded' by the Scale of Fires in Australia Right Now." Science Alert, 7 Dec. 2021, www.sciencealert.com/professional-fire-watchers-astounded-by-the-scale-of-fires-in-australia-right-now. Accessed 18 Nov. 2024.

Thackway, R., and I. D. Cresswell, eds. An Interim Biogeographic Regionalization for Australia. Canberra: Australian Nature Conservation Agency, 1995.

Traill, Barry. “Voracious and Plentiful, Feral Camels Remain a Major Threat to Australian Outback.” Pew Trusts, 21 Feb. 2017, www.pewtrusts.org/en/research-and-analysis/articles/2017/02/21/voracious-and-plentiful-feral-camels-remain-a-major-threat-to-australian-outback. Accessed 18 Nov. 2024.

Wild Australia Program: Pew Environment Group. “Conservation of Australia's Outback Wilderness.” 2008. www.pewtrusts.org/-/media/legacy/uploadedfiles/peg/publications/report/conservation20of20australias20outback20wildernesspdf.pdf. Accessed 18 Nov. 2024.