Ruqayyah Snyder
Australia is the driest inhabited continent in the world. 70% of the country is arid or semi-arid land, with the latter defined as areas receiving an average rainfall of 250-350mm and the former, 250mm or less. The country's geographical position is a contributing factor to its arid climate: Australia is south of the high-moisture tropical belt that Indonesia and New Guinea are in, and sits under the subtropical high-pressure belt, which prevents the lifting of air required for rain. The coastal areas of Australia get a lot of rain, but this drains the moisture from the air, leaving the core of the continent dry.
| Characteristics | Values |
|---|---|
| Australia's geographical position | South of the high-moisture tropical belt |
| Climate | Subtropical high-pressure belt, which prevents the lifting of air required for rain |
| Annual rainfall | 81 to 250 mm (semi-arid), with some areas receiving less than 150 mm |
| Average temperature | Summer: 32-50°C, Winter: 18-23°C |
| Number of thunderstorms | 15-20 annually |
| Vegetation | Acacia species, cypress pines, beefwood, shrub savannas, bluebush, saltbush, eucalyptus woodland, grasses, Chenopodiaceae shrubs |
| Soil | Sand, lime, loam, clay |
| Arid zone | Areas with average rainfall of 250mm or less |
| Semi-arid zone | Areas with average rainfall between 250-350mm |
| Rangelands | 81% of Australia, including arid, semi-arid, and seasonally high rainfall areas |
| Indigenous people | Many Indigenous people live in the rangelands, which are culturally important |
| Economic activities | Mining, tourism, pastoralism, and agriculture |
| Biodiversity | Threatened by wildfires, feral animals, weeds, uncontrolled grazing, and agricultural activities |
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What You'll Learn
Australia's geographical position
The coastal areas of Australia receive a lot of rainfall, but this drains the moisture from the air, leaving the core of the continent dry. In contrast, New Zealand, which is much narrower, allows clouds to rain on the entire subcontinent.
Australia's lack of significant mountain ranges also contributes to its arid climate. The geography of a region plays a crucial role in forcing moisture-laden air upwards to seed mountains and glaciers with snow, forming river systems. However, Australia's relatively flat terrain prevents this process from occurring, further contributing to its arid conditions.
The absence of mountains also means that there are no glaciers to provide a consistent water source during warmer periods. This contrasts with other regions, such as North and South America, where mountain ranges and glaciers play a vital role in the formation of river systems and water supply.
Additionally, Australia's size and isolation contribute to its unique climate. The continent is vast, and its isolation from other landmasses means that it is surrounded by ocean on all sides. This isolation can influence weather patterns and moisture levels, further contributing to the arid conditions in the country's interior regions.
The combination of these geographical factors results in Australia's arid climate, with approximately 70% of the continent classified as arid or semi-arid. This unique climate supports a diverse range of ecosystems, including tropical savannas, woodlands, shrublands, and grasslands, many of which are relatively undisturbed by human activity.
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The subtropical high-pressure belt
Australia's climate is largely determined by the hot, sinking air of the subtropical high-pressure belt, also known as the Australian High. This belt is one of several regions of semi-permanent high atmospheric pressure located over the oceans between 20° and 40° of latitude in both the Northern and Southern hemispheres. The circulation around the highs is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
The latitudes about 30 degrees north and south of the equator, known as the horse latitudes, fall within the subtropical high-pressure belt. These latitudes are characterised by sunny skies, calm winds, and minimal precipitation. The horse latitudes are also associated with the subtropical anticyclone, with the belt in the Northern Hemisphere referred to as the "calms of Cancer" and its counterpart in the Southern Hemisphere known as the "calms of Capricorn".
The subtropical ridge, a feature of the subtropical high-pressure belt, plays a crucial role in influencing monsoon regimes and the tracks of tropical cyclones. During the summer, the subtropical ridge moves poleward, reaching its highest latitude in early autumn before retreating during the colder season. The El Niño–Southern Oscillation (ENSO) can displace the subtropical ridge, impacting the formation and paths of tropical cyclones.
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The Outback
Australia is the driest inhabited continent in the world, with 70% of its land being arid or semi-arid. The Outback, a vast, remote area covering 5.6 million square kilometres, is an integral part of Australia's heritage, history, and folklore. It is known for its arid red deserts, but it also includes tropical and monsoonal climates in the north, savannas, woodlands, rocky hills, floodplains, and vast stretches of wilderness.
Planning and preparation are essential when visiting the Outback. It is recommended to set aside at least five to seven days to fully experience the main sites. Accommodation can fill up quickly during the peak season from May to September, so advance booking is advised. Visitors should also consider downloading offline maps and essential apps, as mobile coverage may be unreliable.
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The Great Artesian Basin
Australia is the driest inhabited continent in the world, with 70% of its land considered arid or semi-arid. The country's arid zone is defined as areas that receive an average rainfall of 250mm or less, with a massive evaporation rate.
The water in the GAB is held in a sandstone layer formed during the Triassic, Jurassic, and early Cretaceous periods. During these periods, much of inland Australia was below sea level, and sandstone was covered by a layer of marine sedimentary rock, trapping water in the sandstone aquifer. The water temperature in the basin ranges from 30 to 100 °C.
The GAB is a vital resource for pastoral, agricultural, and extractive industries, as well as town water supplies and springs, which support unique ecological communities. The discovery and use of the GAB allowed the settlement of thousands of square kilometres of land away from rivers, that would otherwise have been unavailable for pastoral activities.
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The impact on wildlife
Australia is the driest inhabited continent in the world, with 70% of the land considered arid or semi-arid. The arid zone is defined as areas that receive an average rainfall of 250mm or less, while the semi-arid zone receives between 250 and 350mm. These areas bear a legacy of degradation and species loss due to unsustainable land management practices.
The impact of arid conditions on wildlife in Australia is significant. The most common creatures in Australia's arid regions are insects, such as termites and ants, which thrive in these environments. However, the number of animal species in arid regions is significantly lower than in coastal regions.
Arid zone habitats are full of life, including tall shrubs, heath, grasslands, sandy areas, and rocky outcrops. Tall shrub areas are home to small eucalypt, mulga, and acacia trees, which have deep roots to access water. Heath areas are covered in bluebush and saltbush plants, which grow close to the ground. Spinifex grasses, with their hard, spiky leaves, are well-adapted to arid conditions as they minimise water loss.
The dry riverbeds of the arid zones are lined with eucalyptus woodlands, with grasses growing beneath. Chenopodiaceae shrubs, usually no taller than 5 feet, are found in the southern desert areas. The Witchetty Bush, at the eastern end of the arid zone, is home to the endemic species Acacia kempeana, which feeds the witchetty maggot, an important part of the Aboriginal diet.
Semi-desert grasslands with mulga bushes (Acacia aneura) are also common in large areas of the desert. These areas are threatened by bushfires, which are often ignited by spinifex grasses, as well as deforestation, extensive livestock farming, and fuel wood production. Grasslands in the desert areas of the Northern Territory, South Australia, and western Queensland are characterised by grasses of the Astrebla genus.
The management of arid lands in Australia is a complex issue. Pastoralism is the most extensive industry, and there is a focus on integrating conservation and production for sustainable land use. Unambiguous financial assistance for managers in marginally productive livestock areas can help ensure sustainable practices and the management of feral animals, weeds, and fires.
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Frequently asked questions
Yes, Australia is an arid country. 70% of the country is arid or semi-arid land.
Australia's geographical position is a major factor. It is located south of the high-moisture tropical belt and under the subtropical high-pressure belt, which prevents the lifting of air required for rain. The country's size and lack of significant mountain ranges also contribute to its arid climate.
Arid regions in Australia are characterised by low rainfall and variable climates. The average annual rainfall in the Australian desert ranges from 81 to 250 mm, but evaporation rates are high. Temperatures in arid regions can exceed 35°C in summer and range from 18°C to 23°C in winter. These areas are also prone to bushfires and are home to unique flora and fauna, including many endemic species.
