Northern Arid (Province 8)
This province comprises northern South Australia from the N.S.W. and Queensland borders to the Western Australian border. Its southern limit extends from Lake Frome and the northern Flinders Ranges westward to the northern margin of the Nullarbor Plain.
The province has a very hot dry desert climate with short cool to cold winters and an extremely low, unreliable rainfall with no distinct seasonal pattern. The highest mean annual rainfall occurs in the Musgrave Ranges of the far north-west where it reaches 200 mm, with most of the remainder of the province having a mean annual rainfall of around 150 mm, but in the Simpson Desert and Cooper Creek areas this decreases to around 125 mm per annum. Temperatures vary from cold in winter to hot in summer, and seasonal and diurnal ranges are very high. Seasonal ranges tend to increase towards the north and east. Mean annual evaporation is extremely high, increasing from around 3100 mm in the south-west to 4000 mm in the central north. In general the soils of the province are moderately deep to deep and therefore able to store much of the irregular precipitation. Run-off from ranges and hills and the large areas of bare rock, increases the water available for local storage.
About 60% of the central and eastern sections of the province are under pastoral lease and used for extensive livestock grazing. The holdings vary considerable in size, from 2000 km2 in southern parts to over 30 000 km2 in outlying northern areas. South of the dog fence sheep provide the majority of livestock; north of it, cattle. Livestock figures between 1965 and 1974 average about 50 000 cattle in the north-east, 70 000 cattle in the centre and central north and 3000 cattle and 265 000 sheep south of the dog fence. In the east and north-east holdings include much country which is not suitable for even the most extensive form of permanent grazing, and livestock are concentrated along the watercourses and in interdunal areas with bores for stockwater. Drought represents the major environmental hazard in the province and livestock numbers vary greatly through time.The opal mining activities at Coober Pedy and the open-cut coal mine at Leigh Creek support over half of the province's population of less than 4000 people.
There are three conservation areas in the province, which together comprise 5% of its area, and a further 21% has no defined use. Nevertheless, habitat destruction by domestic and feral grazing animals such as sheep, cattle, rabbits, goats, donkeys and camels, and predation by introduced cats, foxes and, perhaps to a lesser extent, dogs has caused both a dramatic decline in numbers and a considerable restriction in range of many native desert-dwelling animals throughout the entire province.
The Amata Aboriginal Reserve occupies the north-west corner and 13.5% of the province.
Four environmental regions have been distinguished in this province:
Northern Uplands and Alluvial Plains (Environmental Region 8.1)
This region comprises the rugged granite and metamorphic Mann and Musgrave Ranges in the far north-western corner which rise abruptly from the surrounding plain. Most streams terminate as floodouts on fans and plains a short distance from the ranges. The ranges and plains are dominated by hummock grasslands, but sparse shrubs of mulga and witchetty bush also occur. The floodplains carry Mitchell grass grasslands and low coolibah woodlands.
Western Sandplains (Environmental Region 8.2)
This region consists of most of the eastern half of the Great Victoria Desert which rises gently from about 200 m above sea level in the south to 700 mm in the north, and represents an old erosional surface veneered with aeolian sand. Longitudinal dunes with an easterly trend cover almost the entire region. The dunes average about 20 m in height and may reach over 100 m in length. Mallee shrubland and woodlands, characteristically of marble gum or mulga, occupy the sandplains and interdune lows. An understory of hard spinifex is typically associated with the eucalypts; one of the tufted grasses is typical with the mulga. On the dunes, hard spinifex merges with needlebush and occasional mallee. Numerous granitic inselbergs rise abruptly through the sandplain. The large of these collect considerable run-off and generate drainage channels which extend some distance into the desert, consequently numerous small claypans and salt lakes have developed, the margins of which carry a samphire vegetation.
Central Tablelands (Environmental Region 8.3)
This region consists of the gibber plains on the western side of the Lake Eyre Basin. These stony surfaced plains with red duplex soils form a relatively well-defined eastern boundary to the Great Victoria Desert although quite a number of dunes extend across them. Where sand sheets or dunes extend across the plain tall shrubland or low open woodlands with an understory of hard spinifex or tufted grasses occur. The exposed gibber, in very few areas, carries a tall open shrubland which includes some mallees, but more commonly, a low shrubland of saltbush and bindyi. Uplift in the western Lake Eyre Basin has led to erosion and dissection of the duricrust surface and the formation of low but steep escarpments sparsely vegetated with saltbush and bindyi. The plains below the escarpments consists of a slightly higher and older plains with gypsum crusting and a lower plain which is graded to the present Lake Eyre. A low but distinct gypcrete escarpment separates the two plains. These plains carry low open mulga woodlands over saltbushes and tufted short grasses, and low shrublands of various saltbushes, bindyi and bluebush.
Lake Eyre Basin (Environmental Region 8.4)
This region is a vast area of aeolian sand accumulation with an exceptionally regular pattern of longitudinal dunes which gradually changes from an easterly alignment in the north. These are the dunes of the Simpson and Strzelecki Deserts. They extend longitudinally without interruption over distances extending 100 km and, in a transverse direction, their frequency varies from about 3 to 6 per km. The upper slopes and crest are sparsely vegetated with sandhill canegrass and hard spinifex. The flanks are well or sparsely vegetated depending on seasonal conditions, with sandhill wattle, needlebush and whitewood which form a variably dense upper story over tufted grasses, forbs, undershrubs and ephemeral herbs. The string of large salt lakes which fringe the southern margin of the dunefield fluctuate considerable with episodic floodings of the Diamantina and Cooper Creek river systems. They are fringed by samphire and occasionally nitrebush shrublands. Apart from the large salt lakes along the fringe of the dunefields, there are numerous variously sized claypans within the sand deserts. These pans are partly interconnected and allow the formation of a vast sheet of water during floods. They carry a variety of vegetation types ranging from low samphire and saltbush shrublands to lignum and canegrass. The floodplains and channels of the major river systems such as the Diamantina and Coopers Creek are fringed by woodlands of river red gum, coolibah, coolibah box and bean tree. Sturts Stony Desert which separates the Simpson Desert from the Strzelecki Desert is a large area of gibber with a very sparse shrubland over tufted short grasses. Some sand dunes invade the stony desert which is a remnant of a former tableland with a siliceous duricrust surface. There are a few small remnants of this tableland in the centre of the present plain.
