Location and General Description
The vast Great Victoria Desert extends from the Eastern Goldfields area in Western Australia across the southern parts of central Australia to the Stuart and Gawler Ranges in South Australia. The climate is arid, with mean annual rainfall ranging from below 150 mm to over 250 mm (Laut 1977a, b, Newby 1984). Rainfall is aseasonal, but shows great variability between years. Summers are very hot, with mean maxima during summer between 32°C and 35°C mm (Laut 1977a, b). Diurnal ranges are also large, and overnight minima commonly fall below 0°C during winter. Much of the region is occupied by sand dunes, with areas of calcrete and silcrete (Greenslade et al. 1986, Laut 1977b). Dunes cover low elevation areas, interspersed among low ranges, dissected tablelands, and plains (Van Oosterzee 1991).
Much of the Great Victoria Desert is vegetated by open woodlands, typically eucalypts (Eucalyptus gongylocarpa, E. pyriformis, and E. socialis) with a hummock grass understorey (Triodia spp., largely T. basedownii), mulga (Acacia aneura) with other grasses (Aristida spp. and Plectrachne spp.), or belah (Casuarina cristata) with shrubs (Maireana sedifolia, Dodenaea attenuata) (Boomsma and Lewis 1980, Greenslade et al. 1986, Specht 1972). The ‘Giles Corridor’ is a narrow strip of Acacia vegetation and the only continuous shrubland to completely traverse the Great Victoria Desert. This corridor links the Pilbara region in Western Australia to the Central Ranges by going though the Lake Carnegie region in the Great Victoria Desert and the southern part of the Gibson Desert (Van Oosterzee 1991).
Gibber plains also occur in this ecoregion, consisting of areas in which the soil is covered by a closely-spaced layer of pebbles, and glazed with a thin wind-polished layer of iron oxides. Gibber plains are normally almost devoid of vegetation, but following rains may be densely covered with ephemeral species, especially Fabaceae, Compositae, and Amaranthaceae.
One of the strategies that allows animals to persist in such extreme environments is to be highly mobile and follow favorable conditions across great distances. Consequently endemism is low, especially among birds and larger mammals. Nevertheless, the endangered chestnut-breasted whiteface (Aphelocephala pectoralis) has a relatively restricted range, spanning the eastern parts of this region and the western parts of the adjoining Tirari-Sturt stony desert region (Blakers et al. 1984, Brouwer and Garnett 1990, Hilton-Taylor 2000). The vulnerable malleefowl (Leipoa ocellata) occurs within the Unnamed Conservation, and, although not reported from the region in recent decades, it is conceivable that the enigmatic and critically endangered night parrot (Geopsittacus occidentalis) is still present (Blakers et al. 1984, Brouwer and Garnett 1990).
The Great Victoria Desert also has an exceptionally high diversity of reptiles (Pianka 1984), including the vulnerable great desert skink (Egernia kintorei) (Cogger 2000) which had been considered extinct in South Australia until its rediscovery by Aboriginal landholders in 1998. More than 100 species of reptile have been recorded, with Gekkonidae (e.g. Diplodactylus), Agamidae (e.g. Ctenophorus), Scincidae (e.g. Ctenotus, Egernia, Lerista and Morethia), and Elapidae (e.g. Simoselaps and Suta) being particularly diverse (Cogger 2000). Extensive lizard radiations and speciation occurred all over the arid interior of Australia, largely in response to climatic changes in the late Pleistocene and the associated shifting and isolation of vegetation pockets. An example of this isolation can be seen in the Great Victoria Desert, where a population of Ctentus brooksi is isolated from populations in the Simpson Desert by a narrow strip of scrub vegetation in south-central Northern Territory. Although the barrier is only several thousand years old, distinct subspecies have evolved, with C. b. brooksi found in the Great Victoria Desert (Cogger 2000, Van Oosterzee 1991). Diversification in habitat results in high lizard density: in a portion of the Great Victoria Desert in Western Australia up to 9 different species of geckos may overlap, with species utilizing a wide variety of food and habitats (sandridges, rocky breakaways, and salt lakes) (Van Oosterzee 1991).
Several threatened mammals, the endangered sandhill dunnart (Sminthopsis psammophila), the endangered marsupial mole (Notoryctes typhlops), and the vulnerable mulgara (Dasycercus cristicauda) still occur within the region (Strahan 1995). Australia has experienced nearly half of the world’s mammal extinctions within the past 200 years, with most of the extinctions concentrated in drier interior regions of the continent (Short and Smith 1994). These extinctions include a number of species which once utilized the Great Victoria Desert: the pig-footed bandicoot (Chaeropus ecaudatus), short-tailed hopping mouse (Notomys amplus), long-tailed hopping mouse (N. longicaudatus), and lesser stick-nest rat (Leporillus apicalis). The greater stick-nest rat (L. conditor) has been extirpated from the region and survives only on offshore islands (Strahan 1995). There are no known extinction among the flora, and just one endangered species, the recently described Stemodia haegii (Briggs and Leigh 1996).
Although the low level of threatened species may be an artifact of low collecting efforts, it is also indicative of the relatively low levels of disturbance since European settlement, which is also evidenced by the low incidence of exotic species (Greenslade et al. 1986). The plant associations identified by Davies (1982) as being inadequately conserved in the South Australian part of the region are now effectively conserved in the Pitjantjatjara Lands.
Located north of the dog fence, Australia’s largest mammalian predator, the dingo (Canis lupus dingo), occurs throughout the region. The other notable predators found here are the perentie (Varanus giganteus) and Gould’s goanna (Varanus gouldii) which can both exceed 1.6 m in length (Cogger 2000). Feral foxes (Vulpes vulpes) and cats (Felis catus) also occur (Strahan 1995), and have been implicated in the decline of a number of vertebrate species.
As a consequence of the climate and the geographical isolation of the region, pastoralism and agriculture are not considered viable. Consequently, there has been little land clearance or grazing by domestic stock. A weapons testing range and nuclear weapons test sites are located in this region. Some areas have been disturbed by mineral exploration and mining, but these impacts are low when considered at the regional scale. Furthermore, extensive tracts of land are protected from exploitation. The Unnamed Conservation Park (21,289 km2) on the South Australian – Western Territory border is the largest of South Australia’s conservation areas. A further 103,000 km2 is effectively conserved in the adjacent Pitjantjatjara Lands, which were ceded to traditional landowners by the South Australian Parliament in 1981. In Western Australia, some 20 percent (5,000 km2) of the Great Victoria Desert Nature Reserve falls within the region.
Types and Severity of Threats
A series of nuclear weapon trials were conducted at Maralinga and Emu by the United Kingdom between 1953 and 1963, as a result of which a number of sites were contaminated with radionuclides (Dept. P.I.E. 1990). The presence of plutonium-239 is of special concern, due both to its long half-life and the risks posed by inhalation. Although a rehabilitation programme was carried out between 1996 and 1999, there remains considerable controversy as to its effectiveness.
There has also been disturbance associated with the Woomera rocket and weapons testing range, primarily through road-building. The increasing popularity of 4WD vehicles presents the potential threat of disturbance in the vicinity of any tracks in this region, although this is not a problem in the Woomera Range, Maralinga, and the Pitjantjatjara Lands where public access is strictly regulated. The main sources of widespread disturbances come from feral animals, especially rabbits (Oryctolagus cuniculus) which adversely affect native vegetation. House mice (Mus musculus) can be highly abundant after good rains, and may adversely affect smaller native mammals.
Justification of Ecoregion Delineation
The Great Victoria Desert ecoregion comprises the IBRA of the same name (Thackway and Cresswell 1995). This active sandridge desert is characterized by Eucalyptus gongylocarpa, mulga, and E. youngiana over hummock grassland dominated by Triodia basedownii.
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Prepared by: Graeme T. Hastwell