Features of South Australia

Australia is a country of contrasts made up of 89 bioregions and 419 subregions, all with distinctly different climates, landforms, geology and species. South Australia has 17 terrestrial bioregions and 8 marine bioregions.

Australia’s landscape has been subject to extensive weathering over the ages, resulting in a flat geology and low levels of nutrients in its soils and oceans. Its rivers have the world’s lowest amount of discharge into the sea for any continent. This lack of discharge has had a major influence on the physical shaping of the coast’s geomorphology.

Over 80% of SA is less than 300 metres above sea level. Mount Woodroffe, in the northwest corner of the state, is the highest peak at 1,435 metres. The lowest place in SA (and Australia) is Kati Thanda–Lake Eyre at 15 metres below sea level, the vicinity of which is also the area of lowest rainfall in SA and Australia’s.

Kati Thanda–Lake Eyre is Australia’s largest salt lake covering 9,500 km², and is found within a major internal river drainage system of the lowlying interior. It is really two lakes connected by a narrow channel. Almost three-quarters of the runoff that flows into the lake finds its way via an intricate network of channels, known as the Channel Country, through the deserts to the lake’s north and east.

Although most of Kati Thanda–Lake Eyre’s water is lost through evaporation or absorption, on the rare occasions when the lake fills, it temporarily becomes Australia’s largest lake spreading out over a vast area and reaching almost 6 m at its deepest point. It then becomes a wildlife haven and is renowned for the swift return of primitive fairy shrimps, fish and vast numbers of breeding birds, including pelicans.

South Australia’s largest river, the River Murray, weaves through 650 km, ending a 2,530-km journey from near Mount Kosciuszko in the Australian Alps to its mouth near Goolwa.

In 2008, Geoscience Australia reported rocks, found on SA’s Eyre Peninsula, dating back around 3,150 million years, confirming one of the oldest landscapes on earth.

The Flinders Seismic Zone in South Australia is one of the most seismically active regions in Australia, with earthquakes of magnitude up to 6.5 recorded on the Richter scale. This region lies within the South Australian Heatflow Anomaly comprising some of the world’s highest concentrations of heat‑producing elements. Major fault displacements, with the uplift of the Mount Lofty Ranges to more than 700 m above sea level, are a testament to the tectonic activity in this region.

South Australia is divided into 3 biomes (areas with similar climates and ecosystems). Two of these are land (arid and Mediterranean) biomes and the third is a marine biome (Figure 2).

The arid biome, covering 87% of SA, has a warm-to-hot and dry climate with low and erratic rainfall. The south has mostly winter rains with summer rains in the north.

The Mediterranean biome, making up the remaining 13%, has a cool-to-warm climate, with a tendency for winter rains.

The marine biome, covering the equivalent of 6% of SA’s land area, has variable and diverse currents with low-nutrient, sheltered and salty gulf waters, with warmer waters in the Great Australian Bight and cooler, nutrient-rich waters in the southeast.

South Australia’s rainfall and temperature are highly variable, both in range and location. Since our last 5-yearly review of the environment, there have been record warm spring seasons, and the 2016–17 summer saw prolonged and extreme heat across the state. Winter warm spells are lasting longer, occurring more often and becoming more intense. Australia had its warmest winter on record in 2017 for average maximum temperatures, reaching nearly 2°C above average.

There has been a clear decline in SA rainfall since 1970, especially over the cooler April to October growing season. The frequency of heavy rainfall has decreased, and this trend is expected to continue. Decreases in rainfall and rising temperatures are driving an increase in the occurrence of dangerous bushfire weather in spring and summer. In September 2017, state fire agencies issued severe to extreme fire weather warnings and Forest Fire Danger Index values exceeded extreme levels at many sites, as large parts of South Australia and New South Wales experienced temperatures that were more than 12°C warmer than the long-term average for this time of year.

Severe storms in 2016 caused damage throughout SA, including widespread power outages. In September, a once-in-50-year storm knocked down more than 20 major electricity pylons and 3 of the state's 4 major transmission lines. The cascading chain of events led to a statewide blackout when the interconnector linking it with Victoria was overloaded. On 7 December, a wind gust of 141 km/h was observed at Moonta as thunderstorms crossed the state, which is the highest wind speed to be recorded in SA since 31 December 2009.

Agriculture covers around 53% of the state, with 42% used for grazing of native vegetation and the remainder cleared for cropping, modified pastures and horticulture. The highest proportion of Australia’s vineyards are in the major growing areas of the Barossa, Clare, Riverland, Adelaide Hills, Fleurieu Peninsula and Coonawarra regions. Cattle are raised mainly in the Adelaide Hills, the Lower South East and Far North districts. Dairying is concentrated in the Adelaide, Lower South East and Lower Murray districts. Grain cropping is focused north and east of Adelaide, and on Yorke and Eyre Peninsulas.

Annual rainfall across these cropping regions ranges from 300 mm at Ceduna, 570 mm at Clare, 335 mm at Lameroo in the east and 575 mm at Naracoorte in the southeast. The C3 cereal crops (wheat, barley, oat and triticale) account for more than 80% of SA’s cropping area, with a range of grain legumes and canola making up the balance. Much of the cropping area is dominated by coarse textured and low fertility soils, although there are significant grain cropping regions with highly productive soils and climates.

Most of our urban land use is centred around Adelaide (see Figure 2), with a population density of 400 people per km² compared with the South Australian average of 1.7 persons/km². Similar to Adelaide, most of the other urban areas in South Australia are located on or close to the coast. This includes the cities of Mount Gambier, Port Pirie, Port Augusta, Whyalla and Port Lincoln.

The Protected Areas System covers 28,195,000 ha (29%) of SA. Only 30% of Interim Biogeographic Regionalisation of Australia (IBRA) Associations in SA are adequately protected, ranging from 81% in the Alinytjara Wilurara Region to just 8% in the Northern and Yorke region.

Pastoral properties, which make up about 40% of land in South Australia, feature native vegetation that has important ecological significance. Pastoral properties are managed through leases under the Pastoral Land Management and Conservation Act 1989 that require regular assessment of land condition to ensure adequate protection of biodiversity. Figure 3 provides a snapshot of the general features of our environment.

South Australia is home to many extraordinary animals, 6 of which are on the IUCN list of the top 20 most endangered in Australia – the Woylie, Numbat, Kangaroo Island Dunnart, Western Quoll, Mala and Black-footed Rock Wallaby.