Nature of the NT
Nature is one of the Northern Territory's greatest assets. We are fortunate in having some of Australia's most beautiful natural places, some of the least disturbed environments in the world, and some extraordinary wildlife. This section provides a brief overview of the nature of the Territory. More detailed information is also available via the menu system for particular environments, bioregions, plants, animals, and conservation management issues.
The Northern Territory occupies an area of about 1,364,000 km2, or about one-sixth of Australia's land area. Within this area, the Territory includes three of Australia's largest islands - Groote Eylandt, Bathurst Island and Melviille Island, and very many smaller islands. The Territory coastline totals about 13,500 km.
A series of permanent large rivers drain northward into the Joseph Bonaparte Gulf (Keep, Victoria, Daly and Fitzmaurice Rivers), into the Arafura Sea (Adelaide, Mary, South Alligator, East Alligator, Goomadeer, Mann, Liverpool, Goyder and Glyde), and eastward into the Gulf of Carpentaria (Roper, McArthur, Robinson, Limmen Bight and Calvert). Inland, most watercourses are ephemeral (notably the Todd and Finke), and many flow into land-locked lakes. There are many wetlands, including permanent swamps (most notably the Arafura Swamp in central Arnehm land), vast seasonally inundated floodplains, pemanent and semi-permanent freshwater lake systems on the Barkly Tablelands, and ephemeral saline lakes in central Australia.
Much of the Territory is relatively flat, but generally disconnected ranges provide a very notable exception. In the north of the Territory, the most spectacular of these ranges is the sandstone escarpment and plateau of western Arnhem Land (partly included within Kakadu and Nitmiluk National Parks). Other spectacular topographic features in the north of the Territory include the sandstone ranges and mesas of the Victoria River District (with some of the most impressive examples of these lying within Keep River and Gregory National Parks), the "lost city" formations in parts of the Gulf hinterland (such as in the Abner Range and within Limmen Gate National Park), and linear escarpments of China Wall near Wollogorang. Long mountain ranges are more a feature of central Australia, and these include some spectacular natural features, such as the MacDonnell Ranges (much of it within national parks), the Petermann Ranges, and Harts range. The Territory's highest peak, Mt Ziel (1531m) lies within the West MacDonnell Range. Central Australia also boasts the extraordinary monolith of Uluru.
Land tenure in the Territory can be simplified into three broad types - pastoral, Aboriginal, and conservation reserves, although some Aborignal lands are used for pastoralism, and others (such as Kakadu) are managed as National Parks. Pastoral lands occupy about 45% of the Territory and Aboriginal lands about 50%. The pastoral properties include some of the largest in Australia, with many leases between 5,000 and 10,000 km2. Large blocks of land held under inalienable Aboriginal Land Title include Arnhem Land and the Central Deserts.
Most of the Territory lies within the tropics, with the Tropic of Capricorn passing just north of Alice Springs.
The Territory's coastline has changed markedly over the last 20,000 years. Rapid sea level rise, in pulses between 8,000 and 20,000 years ago, led to the sinking of a land bridge to New Guinea, the inundation of the Gulf of Carpentaria, the loss of a direct land connection to Cape York Peninsula, and the isolation of Groote Eylandt, the Tiwi Islands and most other islands.
Climate is one of the main determinants of environmental variation in the Northern Territory. From the north to the south of the Territory, the climate varies gradationally from relatively high rainfall monsoonal to arid. The Territory's highest annual rainfall is about 1800 mm, on the Tiwi Islands. This falls to less than 100mmm median annual rainfall in the extreme south-east (the Simpson Desert).
In the north, rainfall is strongly seasonal, with about 90% of annual rainfall falling within the 4 or so months of the wet season (typically November to March). This is a time of heavy tropical downpours, and high temperatures and humidity. The "build-up" to the wet season (October-November) is characterised by a very high incidence of lightning strikes. Destructive cyclones are a recurring feature of the wet season. This extreme seasonality controls many features of the ecology of the Territory's natural systems, including the timing of leaf fall, flowering and fruiting in plants, and of breeding, migration and activity patterns in animals. Many plants in the north of the Territory are deciduous in the late dry season. Many others are annuals, that appear only fleetingly during the wet season. The most seasonal environments are the extensive floodplains of the lower reaches of the large watercourses, which change from dry grasslands in the dry season to vast lakes, supporting hundreds of thousands of waterbirds, in the wet season.
The lack of rain during the dry season cures the grass and other understorey vegetation, developing a highly flammable, dense and extensive fuel load; and, as a result, fire is a frequent and almost inevitable process. The most intense fires typically occur in the late dry season, when fuels are at their driest, and when the frequent lightning strikes are main ignition sources.
In central Australia, climate is still highly seasonal, but rainfall patterning varies markedly between years. Drought is a feature of the history of this land, but heavy rainfalls, often associated with distant cyclonic activity, also occur and may result in sudden flood events in the desert. Temperatures in central Australia may become very hot (more than 40oC) in the summer months, and very cold (-10oC) in the winter. This climatic variation influences what wildlife you may see. For example, many reptiles are largely inactive in the central Australian winter, and hide underground during the heat of the day in the hot summer months.
The Territory's climate has been buffeted by some very marked and rapid oscillations over the last 20,000 years. These have purged some of the biotra, and left others with relict distributions in climatically sheltered areas.
More details of the Territory's weather and climate can be found at the Bureau of Meteorology.
Reflecting the major variation in climate, there is a high diversity of environments across the Territory. The most extensive are the hummock grasslands ("spinifex") and shrublands of the deserts, eucalypt woodlands and open forests across most of the north of the Territory, and woodland and shrublands dominated by Acacia species (including mulga, gidgee and lancewood). Among these vast landscapes, there are smaller areas of rainforest, mangroves, heathlands, swamps, paperbark forests, riparian areas, and other environments, described in more detail in link to environments.
Flora and fauna
Suggestions for further reading
- Williams RJ, Duff GA, Bowman DMJS, Cook GD (1996). Variation in the composition and structure of tropical savannas as a function of rainfall and soil texture along a large-scale climatic gradient in the Northern Territory, Australia. Journal of Biogeography 23, 747-756.
- Wilson BA, Brocklehurst PS, Clark MJ & Dickinson KJM (1990). Vegetation Survey of the Northern Territory, Australia. Technical report no. 49, Conservation Commission of the Northern Territory, Darwin.
- Woinarski JCZ, Fisher A, Milne D (1999). Distribution patterns of vertebrates in relation to an extensive rainfall gradient and variation in soil texture in the tropical savannas of the Northern Territory, Australia. Journal of Tropical Ecology 15, 381-398.