Australia lacks mountains of great height; it is one of the world's flattest landmasses. The average elevation is about 300 m (about 1,000 ft). The interior, referred to as the outback, is predominantly a series of great plains, or low plateaus, which are generally higher in the northeast. Low-lying coastal plains, averaging about 65 km (about 40 mi) in width, fringe the continent. In the east, southeast, and southwest, these plains are the most densely populated areas of Australia.In the east the coastal plains are separated from the vast interior plains by the Great Dividing Range, or Eastern Highlands. This mountainous region averages approximately 1,200 m (approximately 4,000 ft) in height and stretches along the eastern coast from Cape York in the north to Victoria in the southeast. Much of the region consists of high plateaus broken by gorges and canyons. Subdivisions of the range bear many local names, including, from north to south, the New England Plateau, Blue Mountains, and Australian Alps; in Victoria, where the range extends westward, it is known as the Grampians, or by its Aboriginal name, Gariwerd. The highest peak in the Australian Alps, and the highest in Australia, is Mount Kosciusko (2,228 m/7,310 ft), in New South Wales.
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A section of the Great Dividing Range is in Tasmania, which is located about 240 km (about 150 mi) from the southeastern tip of the continent and is separated from it by Bass Strait. The waters of the strait are shallow, with an average depth of 70 m (230 ft). The major islands in the strait are the Furneaux Group and Kent Group in the east, and King, Hunter, Three Hummock, and Robbins islands in the west.The western half of the continent is a great plateau, about 300 to 450 m (about 1,000 to 1,500 ft) above sea level. The Great Western Plateau includes the Great Sandy, Great Victoria, and Gibson deserts. Western Australia has, in its northern half, several isolated mountain ranges, including the King Leopold and Hamersley ranges. The interior is relatively flat except for several eroded mountain chains, such as the Stuart Range and the Musgrave Ranges in the northern part of South Australia and the Macdonnell Ranges in the southern part of the Northern Territory.
The central basin, or the Central-Eastern Lowlands, is an area of vast, rolling plains that extends west from the Great Dividing Range to the Great Western Plateau. In this region lies the richest pastoral and agricultural land in Australia. Uluru (Ayers Rock), in the center of Australia in Uluru-Kata Tjuta National Park, is believed to be the largest monolith in the world. It is 9 km (6 mi) around its base and rises sharply to some 348 m (1,142 ft) above the surrounding flat, arid land. Other mountain ranges of limited size in the central part of Australia are the Flinders Ranges and Mount Lofty Ranges in South Australia. The area along the south central coast is called the Nullarbor Plain. The Nullarbor is a vast, arid limestone plateau that is virtually uninhabited. It has an extensive system of caverns, tunnels, and sinkholes that contain valuable geological information about life in ancient Australia. Extinct volcanic craters are located in the southeastern part of South Australia and in Victoria.
The coastline of Australia is generally regular, with few bays or capes. The largest inlets are the Gulf of Carpentaria in the north and the Great Australian Bight in the south. The several fine harbors include those of Sydney, Hobart, Port Lincoln, and Albany.
The Great Barrier Reef is the largest known coral formation in the world. It extends some 2,010 km (some 1,250 mi) along the eastern coast of Queensland from Cape York in the north to Bundaberg in the south. The chain of reefs forms a natural breakwater for the passage of ships along the coast.
A. Geology
Australia was once part of the enormous landmass Gondwanaland, which earlier formed part of the supercontinent Pangaea. Much of its geological history is remarkably ancient; the oldest known rock formations date from 3 billion to 4.3 billion years ago.
The great plateau of western Australia is underlain by a vast, stable shield of Precambrian metamorphic and igneous rocks, ranging in age from 570 million to 3 billion years old. These form the core of the ancestral continent, which, with Antarctica, had split off from Gondwanaland during the Jurassic Period, less than 200 million years ago, and had begun drifting eastward (see Plate Tectonics). Australia began to assume its modern configuration by the Eocene Epoch, some 50 million years ago, when Antarctica broke away and drifted southward.The thick sedimentary rocks of the Great Dividing Range were deposited in a great north-south trending geosyncline during an interval that spanned most of the Paleozoic Era (570 million to 225 million years ago). Compressive forces buckled these rocks at least twice during the era, forming mountain ranges and chains of volcanoes.
B. Rivers
The Great Dividing Range separates rivers that flow east to the coast from those that flow across the great plains through the interior. The most important of the rivers that flow toward the eastern coast are the Burdekin, Fitzroy, Hunter, and Nepean-Hawkesbury. The Fitzroy River forms a large drainage basin in Queensland. The Murray-Darling-Murrumbidgee network, which flows inland from the Great Dividing Range, drains an area of more than 1 million sq km (400,000 sq mi) in Queensland, New South Wales, Victoria, and South Australia. The Murray River and its main tributary, the Darling, total about 5,300 km (about 3,300 mi) in length. The Murray River itself forms most of the border between New South Wales and Victoria. Considerable lengths of the Murray, Darling, and Murrumbidgee rivers are navigable during the wet seasons.
The central plains region, also known as the Channel Country, is interlaced by a network of rivers. During the rainy season these rivers flood the low-lying countryside, but in dry months they become merely a series of water holes. The Victoria, Daly, and Roper rivers drain a section of Northern Territory. In Queensland the main rivers flowing north to the Gulf of Carpentaria are the Mitchell, Flinders, Gilbert, and Leichhardt.
Western Australia has few major rivers. The most important are the Fitzroy (separate from the Fitzroy in Queensland), Ashburton, Gascoyne, Murchison, and Swan rivers.
Because of Australia's scarce water resources, dams have been constructed on some rivers to supply cities with water and to support irrigation farming. The Snowy Mountains Scheme (1949-1972) and the Ord River Scheme (1960-1972) are the two largest water-conservation projects. The Snowy Mountains Scheme, in the southeastern highlands in New South Wales, is an enormous, multipurpose engineering project that was financed by the federal and state governments to supply water for irrigation, domestic and livestock use, and for the generation of hydroelectricity. The Ord River Scheme is an irrigation project in the remote Kimberley region of Western Australia. During its construction the scheme attracted criticism from economists, environmentalists, and agriculture scientists, and today questions remain about its viability.
C. Lakes and Underground Water
Most of the major natural lakes of Australia contain salt water. The great network of salt lakes in South Australia—Lake Eyre, Lake Torrens, Lake Frome, and Lake Gairdner—is the remains of a vast inland sea that once extended south from the Gulf of Carpentaria. During the dry season many of the salt lakes become salt-encrusted swamp beds or clay pans. Lake Argyle, created by the construction of the Ord River Scheme, is Australia's largest artificially created freshwater lake.Great areas of the interior, which otherwise would be useless for agriculture, contain water reserves beneath the surface of the land. These artesian water reserves, usually found at a great depth, are tapped by drilling to provide water essential for livestock. Artesian water reserves underlie about 2.5 million sq km (about 1 million sq mi) of Australia. The Great Artesian Basin, extending from the Gulf of Carpentaria into the northern part of New South Wales, includes more than 1.7 million sq km (700,000 sq mi). Other artesian basins are in the northwest, southeast, and along the Great Australian Bight.
D. Climate
The climate of Australia varies greatly from region to region, but the continent is not generally subject to marked extremes of weather. The climate ranges from tropical (monsoonal) in the north to temperate in the south. The tropical region, which includes about 40 percent of the total area of Australia, essentially has only two seasons: a hot, wet period with rains falling mainly in February and March, during which the northwestern monsoons prevail; and a warm, dry interval characterized by the prevalence of southeastern winds. Many points on the northern and northeastern coast have an average annual rainfall of 1,500 mm (60 in); in parts of Queensland average annual rainfall exceeds 2,500 mm (100 in). On the fringe of the monsoonal region are the drier savanna grasslands, where the low, unreliable rainfall is supplemented by artesian water. In central and northern Australia average summer temperatures range between 27° and 29°C (80° and 85°F). The deserts of central and western Australia, making up more than two-thirds of the area, have an annual rainfall of less than 250 mm (10 in).
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The warm, temperate regions of southern Australia have four seasons, with cool winters and warm summers. Because Australia is in the Southern Hemisphere, seasons there are the reverse of those in the Northern Hemisphere. January and February are the warmest months, with average temperatures varying between 18° and 21°C (65° and 70°F). June and July are the coldest months, with an average July temperature of about 10°C (about 50°F), except in the Australian Alps, where temperatures average 2°C (35°F). The eastern coastal lowlands receive rain in all seasons, although mainly in summer. The warm, temperate western and southern coasts receive rain mainly in the winter months, usually from prevailing westerly winds. Tasmania, lying in the cool temperate zone, receives heavy rainfall from the prevailing westerly winds in summer and from cyclonic storms in winter. Over the greater part of the lowlands, snow is unknown; however, in the mountains, particularly the Australian Alps in southern New South Wales and the northern part of Victoria, snowfall is occasionally heavy.All of the southern states are exposed to hot, dry winds from the interior, which can suddenly raise the temperature considerably. In most years, parts of the continent experience drought conditions and smaller localities are ravaged by floods and tropical cyclones. Southeastern Australia, including Tasmania, has among the highest incidences of serious bushfires in the world, along with California in the United States and Mediterranean Europe. In 1994, notably, bushfires swept through New South Wales and destroyed several hundred homes in suburban Sydney.
E. Natural Resources
Australia is rich in mineral resources, notably bauxite, coal, diamonds, gold, iron ore, mineral sands, natural gas, nickel, petroleum, and uranium. Readily cultivatable farmland is at a premium because much of the land is desert. Australia, however, has become one of the leading agricultural producers in the world by applying modern irrigation techniques to vast tracts of arid soil.
F. Plants
The continent of Australia has a distinctive flora that includes many species not found elsewhere. Of the 22,000 species of plants in Australia, more than 90 percent occur naturally there. Some 840 species are threatened with extinction, and 83 have become extinct since the beginning of European settlement. Approximately 2,000 plant species are introduced, or nonnative, species. Most have been associated with the development of agriculture and grazing, or with the establishment of large plantations of pines for commercial softwood. The spread of weeds and other aggressive introduced plants into areas of original vegetation is a serious environmental challenge.
Australia's vegetation is predominantly evergreen, ranging from the dense bushland and eucalyptus forests of the coast, to the mulga and mallee scrub and saltbush of the inland plains. The tropical northeastern belt, with its heavy rainfall and high temperatures, is heavily forested. Palms, ferns, and vines grow prolifically among the oaks, ash, cedar, brush box, and beeches. Mangroves line the mud flats and inlets of the low-lying northern coastline. The crimson waratah, golden-red banksias, and scarlet firewheel tree add color to northern forests.
Along the eastern coast and into Tasmania are forests of pine. Pine ranks second to the eucalyptus in terms of economic importance. The Huon and King William pines are particularly valuable for their timber, but the Huon pine is now considered rare and is usually protected. In the forest regions of the warm, well-watered southeastern and southwestern sectors, eucalyptus predominates; more than 500 species are found, some reaching a height of 90 m (300 ft). The mountain ash, blue gums, and woolly butts of the southeast mingle with undergrowth of wattles and tree ferns.
The jarrah and karri species of eucalyptus, which yield timber valued for hardness and durability, and several species of grass tree are unique to Western Australia. The wildflowers of the region are varied and spectacular. In the less dense regions of the interior slopes grow red and green kangaroo paws, scented Boronia, waxflowers, bottle brushes, and smaller eucalypti, such as the stringbark, red gum, and ironbark. More than 500 species of acacia are indigenous to Australia. The scented flower of one acacia, the golden wattle, is the national flower of Australia and appears on the official coat of arms. In the interior region, where rainfall is low and erratic, characteristic plants are saltbush and spinifex grass, which provide fodder for sheep, and mallee and mulga shrubs.
The most valuable native grasses for fodder, including flinders grass, are found in Queensland and northern New South Wales. During occasional seasonal floodings, rapid and luxuriant growth of native grasses and desert wildflowers occurs, and water lilies dot the streams and lagoons.
G. Animals
Unique and primitive forms of animal life exist in Australia. Seven families of mammals and four families of birds are classified as native to the country. About 70 percent of the birds, 88 percent of the reptiles, and 94 percent of the frogs are unique to Australia. Seven of the more than 750 known species of birds have become extinct since the beginning of European settlement, and another 35 are endangered or vulnerable. Of mammals, 19 are extinct and 63 are threatened. Environmentalists have argued for more rigorous conservation policies to protect Australia's unique animal life.One striking aspect of mammal life in Australia is the absence of representatives of most of the orders found on other continents. However, the primitive, egg-laying mammals known as monotremes are found most abundantly in Australia. One of them, the platypus, a zoological curiosity, is an aquatic, furred mammal with a bill like that of a duck and with poisonous spurs. It lives in the streams of southeastern Australia. Another monotreme of Australia is the spiny anteater, or echidna.
Most native mammals are marsupials, the young of which are nourished in an external marsupium, or abdominal pouch. The best-known marsupials of Australia are the kangaroos, which include about 50 species. The kangaroo is vegetarian and can be tamed. The large red or gray kangaroo may stand as high as 2 m (7 ft) and can leap up to 9 m (30 ft). The wallaby and kangaroo rat are smaller members of the kangaroo family. The phalangers are herbivorous marsupials that live in trees; they include the possum and the koala, a popular fur-bearing animal that is protected throughout Australia. Other well-known marsupials are the burrowing wombat, bandicoot, and pouched mouse. The carnivorous Tasmanian devil, principally a scavenger, is found only on the island of Tasmania.
Rodents, bats, and the dingo, or warrigal, belong to a different order of mammals. The dingo is a doglike night hunter that also preys on sheep; it does not bark, but howls.
When Europeans settled in Australia, they brought in many species of animals. The wild descendants of these introduced animals pose serious environmental threats. For example, the European rabbit was brought in mainly for sport in the mid-19th century. These rabbits quickly reached plague proportions in Australia's receptive environment with no natural predators, and their total population has reached as many as 500 million. The damage they cause includes soil erosion, the destruction of habitat for native species, and large commercial production losses. Rabbits, as well as foxes and cats, have been targeted for massive national efforts in biological control and regional eradication programs. Other destructive animals include pigs, goats, cattle, horses, and camels. In the monsoonal areas of tropical Australia, the Asian water buffalo has increased its population over a vast territory; it is responsible for erosion and the disruption of delicate swamp habitats.The continent contains a variety of reptile life. It has two species of crocodiles, the smaller of which is found in inland fresh waters. The larger, fierce saurian crocodile of the northern coastal swamps and estuaries attains lengths of 6 m (20 ft). There are more than 500 species of lizards, including the gecko, skink, and the giant goanna. About 100 species of venomous snakes are found in Australia. The taipan of the far north, the death adder, the tiger snake of southern Australia, the copperhead, and the black snake are the best known of the poisonous snakes.
The waters surrounding Australia support a wide variety of fish and aquatic mammals. Several species of whales are found in southern waters, and seals inhabit parts of the southern coast, the islands in Bass Strait, and Tasmania. The northern waters supply dugong, trepang, trochus, and pearl shell. Edible fish and shellfish are abundant, and the oyster, abalone, and crayfish of the warmer southern waters have been exploited commercially. Australian waters contain some 70 species of shark, several of which are dangerous to humans. The Queensland lungfish, sometimes called a living fossil, is a primitive fish that breathes with a single lung instead of gills.
Most insect types are represented in Australia, including flies, beetles, butterflies, bees, and ants. The giant termites of northern Australia build huge, hill-like nests up to 6 m (20 ft) in height. Australia has earthworms in abundance, including the giant earthworms of Victoria, which range from 0.9 to 3.7 m (3 to 12 ft) in length, the longest in the world.
Australia is the home of 751 known species of birds, ranging from primitive types, such as the giant, flightless emu and cassowary, to highly developed species. The fan-tailed lyrebird has great powers of mimicry. The male bowerbirds build intricate and decorative playgrounds to attract females. The kookaburra, or laughing jackass, is noted for its raucous laughter. Many varieties of cockatoos and parrots are found; the budgerigar is a favorite of bird fanciers. The white cockatoo, a clever mimic, is more common than the black cockatoo. Black swans, spoonbills, herons, and ducks frequent inland waters. Smaller birds include wrens, finches, titmice, larks, and swallows. Gulls, terns, gannets, muttonbirds, albatrosses, and penguins are the most common seabirds. The muttonbird, found mainly on the islands of Bass Strait, is valued for its flesh.
H. Soils
All types of soils are found in varying quantities throughout the continent. Although more than 40 percent of the land consists of desert and sandy plains, suitable in places only for light grazing of sheep, soil resources are a significant factor in the Australian economy. Traditionally, the base of Australia's exports has been supplied by those who farm and graze the land, although the proportion of foreign earnings from farming has declined in recent years.Phosphate additives have been used extensively as soil fertilizers for many years; large areas of marginal land have been made more productive by the use of trace elements, such as zinc, copper, and manganese, and some new lands have been opened up to production. Criticism of the accumulating side effects of soil additives increased during the 1970s and 1980s, when it was demonstrated that soil acidification was affecting vast areas. During the same period, water runoff from fertilized soils was linked with periodic outbreaks of toxic blue-green algal blooms in the Murray-Darling Basin. Elsewhere, wind erosion in the semiarid pastoral and agricultural regions and water erosion in the wetter, deforested southeastern regions pose major problems. A local movement called Landcare won significant government support to address these problems. The ecological and economic threats to the soil and water are being countered by a wide range of technical and educational programs.
I. Environmental Issues
Australia has been an island continent for 200 million years, separated by vast seas from the rest of the world. Because of this isolation, its plants and animals have evolved into some of the strangest species on Earth. No other region has such a diversity of living things unique to its shores.
The isolated development of Australia's native species and biomes has made them fragile and vulnerable to destruction by invading species. Humans have introduced plants and animals from around the world. The first introduced species may have been the dingo, which was probably brought as a domestic animal by aboriginal immigrants from Asia thousands of years ago. These new species have frequently pushed out native species. Famous examples are European rabbits and the North American prickly pear cactus.
Some of the world's most unique habitats, located in Australia, are environmentally threatened. Overuse by tourists and divers and increased industrial shipping in nearby waters has damaged the health of the Great Barrier Reef. The wet tropical forests of northern Queensland are coveted by the timber industry and tourist developments. Preservation of tropical forests remains an active and sensitive environmental issue in Australia.
Australia has an extensive system of terrestrial national parks and reserves, which are administered by the individual states. A number of marine and estuarine reserves have also been designated, including the massive Great Barrier Reef Marine Park. The system includes 11 World Heritage Sites and 12 biosphere reserves designated under the United Nations Educational, Scientific and Cultural Organization (UNESCO) Man and the Biosphere Program. Australia's protected land comprises 7 percent (1997) of the country.
Australia has few permanent rivers, and a great deal of farm water comes from wells that tap a few large underground artesian basins, most of which supply saline water of marginal quality. Salinization and alkalization of soil is common. Soil erosion and desertification due to poor farming practices occurs, especially on overgrazed land. Kangaroos compete with cattle for forage in some regions—the kangaroos are sometimes harvested as a game species for sport and to reduce their numbers.
Australia has developed as a major industrial power with a high standard of living and has thus experienced the accompanying problems of water, soil, and air pollution near its cities. The country is a major source of global greenhouse gas emissions. Many environmental policies are quite stringent, however, such as those governing the recycling and disposal of household waste. The country's greatest environmental asset is its relatively low population—only about 19 million people—giving Australia one of the lowest overall population densities of any country.
Internationally, Australia has ratified numerous environmental agreements to protect the environment and prevent climate change, including agreements to preserve Antarctica's pristine state. Regionally, Australia cooperates with other South Pacific nations in protection of the marine environment. Agreements to protect migratory birds have been made with Japan and China.
