†Recorded extinctions since 1500. *Categories I-IV afford higher levels of protection.
overview
The Southwest Australia Hotspot occupies some 356,717 km² on the southwestern tip of Australia, in the state of Western Australia. As defined, this hotspot comprises the Southwest Botanical Province, but excludes the neighboring Southwestern Interzone. As this hotspot is one of five Mediterranean-type ecosystems in the world, most rain falls during the winter months and the summers are characteristically dry. A broad coastal plain 20-120 kilometers wide grades into gently undulating uplands, with weathered granite, gneiss and lateritic formations. Further inland, rainfall decreases and the length of the dry season increases.
Native plants are well adapted to the nutrient-poor sandy and lateritic soils, which also support broadacre cropping and sheep grazing. Vegetation in the province is mainly woody, comprising forests, woodlands, shrublands, and heaths, but no grasslands. Principal vegetation types in this region are Eucalyptus woodlands, and the Eucalyptus-dominated “mallee” shrubland. Kwongan is a term adapted from the Aboriginal Noongar language to cover the various Western Australian types of shrubland, comparable with the maquis, chaparral, and fynbos of other countries with Mediterranean-type systems. The principal structural types of Kwongan are thicket, scrub-heath, and heath, which together comprise about 30 percent of the original vegetation. A number of vegetation units are endemic, including some types of eucalyptus forests and some forms of kwongan.
The Southwest Australia Hotspot occupies some 356,717 km² on the southwestern tip of Australia, in the state of Western Australia. As defined, this hotspot comprises the Southwest Botanical Province, but excludes the neighboring Southwestern Interzone. As this hotspot is one of five Mediterranean-type ecosystems in the world, most rain falls during the winter months and the summers are characteristically dry. A broad coastal plain 20-120 kilometers wide grades into gently undulating uplands, with weathered granite, gneiss and lateritic formations. Further inland, rainfall decreases and the length of the dry season increases. Native plants are well adapted to the nutrient-poor sandy and lateritic soils, which also support broadacre cropping and sheep grazing. Vegetation in the province is mainly woody, comprising forests, woodlands, shrublands, and heaths, but no grasslands. Principal vegetation types in this region are woodlands, and the -dominated “mallee” shrubland. is a term adapted from the Aboriginal Noongar language to cover the various Western Australian types of shrubland, comparable with the maquis, chaparral, and fynbos of other countries with Mediterranean-type systems. The principal structural types of Kwongan are thicket, scrub-heath, and heath, which together comprise about 30 percent of the original vegetation. A number of vegetation units are endemic, including some types of eucalyptus forests and some forms of kwongan.
Taxonomic Group
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Species
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Endemic Species
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Percent Endemism
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Plants
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5,571
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2,948
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52.9
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Mammals
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59
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12
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20.3
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Birds
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285
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10
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3.5
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Reptiles
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177
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27
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15.3
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Amphibians
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32
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22
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68.8
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Freshwater Fishes
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20
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10
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50.0
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human impacts
The greatest human impact in Southwest Australia has been the clearing of native vegetation for agriculture. Agricultural development began in 1829, with the arrival of the first European settlers to the region. However, because of the poor soils, development progressed slowly until the 1890s, when phosphate fertilizers were introduced. Today, most usable private land in the region is farmed, although it requires the application of phosphate, as well as zinc, copper, cobalt, and molybdenum. Because of the region's long dry seasons, bush fires have traditionally been used for hunting and clearing land. Although native plants are highly adapted to fire, the alteration or intensification of burning regimes can dramatically change the composition and condition of the natural vegetation.
One of the most serious current threats to the natural vegetation of Southwest Australia is the spread of root disease, or "jarrah dieback" caused by the root fungus Phytophthora cinnamomi. The disease was first noticed in the jarrah forests in 1940 but not identified until 1965. By that time, thousands of hectares of forest had been infected and killed. Root disease is now spreading to other habitats, including kwongan shrublands, and in particular Stirling Range National Park, where it has caused mortality among susceptible plants like the grass trees ( Xanthorrhoea spp.) and members of the Proteaceae, especially the Banksias.
Large-scale mining for bauxite is increasingly a threat to Southwest Australia's ecosystems; the region is one of the largest producers of alumina in the world. Open-pit mining destroys habitats and pollutes waterways. However, recent reclamation efforts have been successful at establishing native plants in abandoned mine pits, a technique that holds promise for land management in the region.
Introduced alien species, especially foxes and cats, threaten native fauna and have caused major declines in species like the numbat in Southwest Australia. Land managers have successfully poisoned these alien species with sodium flouroacetate; amazingly, native mammals are immune to the poison because the compound occurs naturally in the leaves of many native legumes.
Today, of the principal vegetation types found in the region, 89 percent of the Eucalyptus woodlands have been lost, while 50 percent of the Eucalypt-dominated mallee and 59 percent of the Kwongan heath formations have been cleared. In total, only 30 percent of the original vegetation remains in more or less pristine condition.
conservation action and protected areas
A total of about 38,000 km², 11 percent of the land area in Southwest Australia, is under some form of official protection, virtually all of it in IUCN categories I to IV. Many reserves, however, are too small to adequately protect biological resources, and many ecosystem types are not well represented in the protected area system. Typically, the region's reserves represent land that was unsuitable for farming in the early days of settlement. Arable lands are almost exclusively privately owned, and a number of rare species are found only on these private lands.
Southwest Australia represents one of the best opportunities for long-term conservation among the hotspots because of its relatively low population density. However, immediate action is necessary to ensure the survival of the region's unique and highly threatened flora and fauna. In addition to maintaining the integrity of existing protected areas, the current network should be expanded through the creation of new reserves from private and public lands to represent species and ecosystems not yet protected.
There are a number of conservation programs and projects currently operating in Southwest Australia. The Western Shield Program, run by the Department of Conservation and Land Management, is working to bring at least 13 native fauna species back from the brink of extinction by controlling introduced predators, the fox and feral cat. The main weapon in the fight against these predators is the use of the naturally occurring poison 1080, found in native plants called gastrolobiums or 'poison peas'. While the native animals have evolved with these plants and have a high tolerance to the poison, introduced animals do not.
Project Eden is the arid scientific conservation component of Western Shield. This project uses innovative techniques to eradicate feral herbivores and predators and rejuvenate 105,000 hectares of arid zone habitat on Peron Peninsula at Shark Bay for threatened native fauna, and, to promote their reintroduction into the area.
A project focused on the ecology, abundance and predator dynamics of threatened Shark Bay mammals, has been run by the Sustainable Ecosystems program of CSIRO, the Australian national research agency, in partnership with a local salt mining community at Useless Loop for the past 16 years. This work has studied in detail the life cycle of some of Australia’s most threatened animals on Bernier and Dorre Islands and has reintroduced the western barred bandicoot and burrowing bettong, two species extirpated on the Australian mainland, to Heirisson Prong.
Other conservation projects in Southwest Australia include community-based recovery programs for the threatened Carnaby's black-cockatoo, western ground parrot, dibbler, noisy scrub-bird and malleefowl. These involve organizations such as Birds Australia, WWF, CSIRO, Department of Conservation and Land Management and local Landcare groups.
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