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BIODIVERSITY AND LAND
Table 24.2 details the current list of threatened species, both flora and fauna, as assessed under the EPBC Act.
Over the last 200 years, elements of Australia's biodiversity have declined and some species of mammals, birds, frogs and plants are presumed to have become extinct. Mammals particularly have been affected, with 27 species that lived in continental Australia at the time of European settlement in 1788, now presumed extinct under the EPBC Act. Ten of those species have been lost since 1900.
Table 24.3 lists the mammal species that are believed to have become extinct in continental Australia since 1788. A further seven subspecies are presumed extinct and several other species now survive on offshore islands or Tasmania but are extinct on the mainland. This compares with 23 extinct birds from about 700 species, four extinct frogs from over 200 species, and 61 extinct flowering plants from over 15,000 species. No freshwater fish or reptile species are known to have become extinct.
PRESSURES ON AUSTRALIA'S LAND RESOURCES AND BIODIVERSITY
Land clearing and fragmentation
Australia's population continues to increase, both in numbers and in affluence, putting great pressure on land and resources. The way in which people use the land has significantly changed Australia's natural systems and landscapes. All uses of land exert pressure on the environment. In the last 200 years, vast areas of native vegetation have been cleared or degraded resulting in adverse effects on biodiversity, soil and water quality and assisting in the spread of weeds, feral pests and diseases.
The impact of broad-scale vegetation clearance on the land and its biodiversity is profound and has been of concern for several decades in Australia. Associated with the loss of native vegetation are a broad range of environmental, economic, and social impacts. Environmental impacts can include habitat loss or fragmentation, loss of ecosystem, species and genetic diversity, reduced water quality in inland and marine environments, reduced carbon storage, and soil degradation. Economic impacts can include costs associated with loss of flood control, deterioration of water quality, loss of habitat for economically important species, loss of tourist potential, and loss of production through soil degradation. Social impacts can include loss of heritage values and loss of recreation and tourism values.
In the decade 1994-2004, although land clearing continued, the rate of clearance decreased by about 40% (graph 24.4). Forest conversion is land cleared for the first time, as opposed to reclearing of previously cleared land. However, these figures do not distinguish between the type of vegetation (native or non-native) that was cleared.
Grazing pressures refers to the effect of grazing by all animals. It not only refers to the impact of domestic livestock such as cattle, sheep and horses but also native and feral grazing animals such as goats, camels, kangaroos and locusts. The combined effect of grazing places significant pressure on Australia's native flora and fauna. Large areas of native grasslands have been lost either as native species have changed as a result of grazing pressure or as a result of agricultural activity as improved pastures have been introduced to support livestock.
Agriculture is the major form of land use in Australia. In 2005, 58% of the Australian land mass was used for agricultural activity, principally grazing and growing crops. Although numbers of cattle and sheep have not increased in recent times, they still continue to place pressure on the land. The number of cattle increased from about 8 mill. in 1905 to nearly 28 mill. in 2005 - in the period 1995-2005 the number increased by only 2 mill. In 2005 the number of sheep and lambs was 54% higher than in 1905 (about 101 mill. compared with 66 mill.). Sheep and lamb numbers in 2005 were considerably lower than in the 1960s, 1970s and late-1980s. The size of the national flock peaked in 1970 at 180 mill. (graph 24.5) (see the Agriculture chapter).
It is not just the number or type of grazing animals but also the availability of water that places pressure on Australia's biodiversity. In the arid zone, despite lower stock densities, the impact of grazing on biodiversity can be greater than it is in high rainfall zones because low productivity limits forage and stock compete with native animals for limited resources. Where water was formerly limiting, the provision of water through bore holes, earth dams and tanks has resulted in the grazing pressure spread more evenly across the landscape so there is now little land left that is only lightly grazed.
Invasive animals, plants and other organisms
The Australian continent’s long isolation from the rest of the world has endowed it with a unique set of plants and animals. Like other islands, isolation has also made the native flora and fauna susceptible to the impact of invasive species. Some introduced species thrive in Australia because the predators and parasites that controlled them at home do not exist in Australia, while some species grow more quickly, breed more prolifically or have more varied diets than their Australian counterparts.
In 2004, 25 mammals, 20 birds, 4 reptiles and 1 amphibian introduced from overseas were recorded as established in Australia. In addition, in 2002 at least 23 exotic freshwater fish species were established.
Introduced predators like the fox and cat have spread over much of Australia and have contributed to the decline or extinction of some native species through predation or the spread of disease. Cane toads have advanced throughout Queensland to Cape York, south to Port Macquarie in New South Wales, and into the Northern Territory, where they have reached Kakadu. They eat mainly insects, but also frogs, small mammals and snakes. Because they are poisonous, cane toads kill many animals that prey on them including goannas, quolls and birds.
Rabbits have at times reached plague proportions over much of Australia, competing with native animals for resources, overgrazing vegetation and digging holes which damage soil structure. Goats strip vegetation, erode slopes and compete with rock wallabies for food and shelter. Donkeys and pigs cause erosion and spread weeds (pigs also eat rare plant species). Commercial honeybees, found in nearly every habitat, compete for nectar with native insects and take over nesting hollows from birds and mammals.
All states and territories have populations of introduced fish. Thirty-five exotic fish species, including European carp, have become established in inland waters, with eight identified as having a significant effect. This does not include the exotic marine animals, often introduced into coastal waters from ships' ballast or by riding on hulls, which can also be a problem.
A plant which has, or has potential to have, a detrimental effect on economic, conservation or social values, is considered to be a weed. The National Weeds Strategy states that weeds are among the most serious threats to Australia’s primary production and natural environment. Weeds are a major problem for farmers as they reduce their agricultural productivity. Weeds were estimated to have cost the Australian economy $4 billion (b) in 2001-02 in lost agricultural production and control costs. There are also flow-on costs to the environment which have yet to be estimated. Weeds displace native species, and the effects flow on to animals that rely on native plants for food and shelter. Some weeds are either more flammable or more fire retardant than the species they displace and can alter the fire patterns of the communities they invade (which may have effects on native animals living in those communities). Other weeds provide food and shelter for invasive animals. About 350 weed species in Australia have been declared noxious. Table 24.6 provides details of the spread of weeds identified as already causing significant environmental damage, so called 'weeds of national significance'.
Other introduced organisms, such as dieback fungus (Phytophthera cinnamomi), invade plant communities, killing selected species, and disrupting ecological processes. Dieback is the most important threat to the biodiversity of the Stirling Range National Park (Western Australia). Some plants (such as banksias and grevilleas) are highly susceptible and 80-100% of infected individuals may die.
Altered fire regimes
Fire has shaped much of the Australian vegetation. Indigenous Australians have used fire widely to manage the vegetation. Since European settlement, experts believe that fires have tended to be less frequent with more fuel to power them, more intense and, in some areas, more destructive as a result. Some well documented changes include:
Altered hydrological regimes
The clearance of native vegetation and commercial changes in hydrological cycles have serious implications for land management and biodiversity. Vegetation clearance changes the water balance of an area and this may lead to fundamental changes in the local soils and climate, as well as the local water table and its chemical composition.
Australia's soils are old and shallow and are susceptible to degradation by agricultural activities. Even in a continent as dry as Australia, salinity occurs when there is too much water. Salinity occurs when the water table rises, bringing natural salts to the surface (in sufficient quantity, these salts are toxic to most plants).
In the quest to prepare Australian soils for agriculture, trees were massively cleared. Yet trees played a crucial role in maintaining the water balance in the ancient soils. It was the success in clearing trees that led to the development of dryland salinity. Irrigated-land salinity is caused by a similar effect - the application of excess water to land causes the water table to rise. European farming practices which replaced native vegetation with shallow-rooted crops and pastures have caused a marked increase in the expression of salinity in land and water resources.
The impacts of salinity are also wider than lost agricultural production and include damage to water resources, biodiversity, pipelines, houses and roads. Salinity harms Australia’s biodiversity (primarily through loss of habitat), while saline water damages bitumen and concrete. In 2000, 1,600 kilometres (km) of rail, 19,900 km of road, 68 towns and 80 important wetlands were at risk of damage from salinity (graph 24.8). The National Land and Water Resources Audit in 2001, estimated that about 5.7 mill. ha (not all of it agricultural land) had a high potential for the development of dryland salinity through shallow or rising water tables. In 2002, 20,000 farms and 2.0 mill. ha of agricultural land were reported by farmers as showing signs of salinity.
Dryland salinity also threatens biodiversity, through loss of habitat on land and in water. Areas near water are often worst affected because they occupy the lowest parts of the landscape where saline groundwater first reaches the surface. Areas of remnant and rehabilitated native vegetation are under threat in Western Australia, South Australia, New South Wales and Victoria. In the Western Australian wheat belt, salinity has caused a 50% decrease in the number of wetland bird species and 450 plant species are threatened with extinction through salinity.
Natural resource management
Australia's salinity problems are the focus of the $1.4b joint Australian Government and State Government National Action Plan for Salinity and Water Quality, endorsed in 2000 by the Council of Australian Governments. Under the plan, 21 priority regions have been targeted and governments and communities are working together to prevent, stabilise and start to reverse trends in dryland salinity, and improve water quality.
Additionally, the Natural Heritage Trust (NHT) was set up by the Australian Government in 1997 to help restore and conserve Australia's environment and natural resources. Its funding has been extended until 2007-08 making it a $3.0b investment. Thousands of community groups and organisations have received funding for environmental and natural resource management projects. The NHT provides funding for environmental activities at a community level (through the Australian Government Envirofund), a regional level, and a national/state level.
More than nine out of ten farmers reported undertaking some form of natural resource management (NRM) activity during 2004-05. Nationally, weed and pest management were the most common NRM activities farmers undertook, with 80% of agricultural establishments undertaking activities to either prevent or manage weeds. Land and soil and native vegetation issues were other natural resource management issues reported by farmers. Native vegetation management also formed an important part of NRM on farms in 2004-05. Approximately 63% of agricultural establishments which reported the presence of native vegetation undertook some form of native vegetation management activities during the year.
Although Australia’s biodiversity continues to be threatened by many factors, much is being done to protect native flora and fauna. One such measure is the protection of land and sea areas (and their biodiversity) inside conservation reserves. National parks and other protected areas are areas of land and/or sea especially dedicated to the protection of biodiversity and other natural and cultural resources. They are established under Commonwealth, state or territory laws or other legal means. All governments participate in the development of a comprehensive, adequate and representative national reserve system as part of Australia's obligation under the United Nations Biodiversity Convention established in 1993. Most national parks and other protected areas in Australia are declared and managed by state and territory governments although, during the last decade, some protected areas have been established which are managed by conservation or other groups. Declaration and management of Indigenous protected areas - Indigenous-owned land that is managed to protect its natural and associated cultural values - commenced in 1998. The Australian Government declares and manages parks and reserves on land owned or leased by the Commonwealth, in Commonwealth waters and on Indigenous land leased to the Commonwealth.
Australia also has international obligations concerning its protected land, such as World Heritage listed sites and Ramsar wetlands. World Heritage sites are nominated areas that have outstanding natural and/or cultural values. Australia has 15 World Heritage sites listed for natural values, with Kakadu National Park, Uluru-Kata Tjuta National Park, Willandra Lakes Region and the Tasmanian Wilderness also listed for cultural values. Ramsar wetlands are wetlands of international importance. They are valued for their ecology, their plants and animals, or for the water bodies themselves and the hydrological functions (such as water filtration) they perform. Australia has 64 Ramsar wetlands and is a signatory to international conventions to protect migratory species that use these wetlands, such as the Japan-Australia Migratory Bird Agreement and the China-Australia Migratory Bird Agreement.
Australia has a series of terrestrial and marine protected areas which are under the control of the Australian, state and territory governments. The area of conservation reserves in each state and territory is recorded in the Collaborative Australian Protected Areas Database (CAPAD) <http://www.deh.gov.au/parks/nrs/capad> using the World Conservation Union (IUCN) classification system of protected areas. The classification system comprises seven categories based on the main (or primary) management intent of protected areas as follows:
Table 24.9 shows the amount of protected land in each category. Most of the land recorded in CAPAD is public land. Some 10.5% of land is protected on the Australian mainland (including Tasmania).
With 63% of Australian land in private ownership, efforts to protect biodiversity now extend beyond the reserve system into some of this private land. This occurs through community landcare groups and conservation agreements made between landholders and governments. Some companies and community groups also operate conservation reserves. Indigenous communities are also involved in managing land, with Kakadu, Uluru-Kata Tjuta and Booderee National Parks all managed jointly with traditional owners and the Australian Government. This provides an emphasis on maintaining and strengthening traditional ties with the land, which relies heavily on ensuring the land and the ecosystems it supports are in good shape.