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Biodiversity Overview

Fourteen specific issues were considered in the 2003 SoE Report with regard to biodiversity. These issues were grouped broadly under the topics of condition, threatening processes and responses. Threatening processes are further classified in terms of habitat change; weeds, pests and diseases; and harvesting of native species. Fourteen specific issues were considered: Biodiversity Health; Special Features; Land Clearance; Urban Growth; Pollution; Introduced Species; Plant Pests (Weeds) and Diseases; Animal Pests; Native Forests; Firewood Collection and Usage; Native Fauna Harvesting; Native Fauna Control and Culling; Fisheries; and Reservation.

Biodiversity is often considered at three levels: ecosystem diversity, species diversity and genetic diversity. The chapter focuses in on terrestrial biodiversity, particularly in relation to ecosystems and species. Other than for commercially valuable species, little is known about genetic diversity.

Threatened Species and Ecological Communities: Since European colonisation, 24 plant and 8 animal species are known to have become extinct in Tasmania. Two acts address threatened species: the Environment Protection and Biodiversity Conservation Act 1999 (Australian Government), and the Tasmanian Threatened Species Protection Act 1995. There are 601 species listed as threatened under the Threatened Species Protection Act 1995, including 11% of Tasmanian mammal species (10 out of 86), 16% of native birds (32 out of 203), 454 species of plants, 14 species of fish, 121 species of invertebrates, and 8 species of reptiles.

Biodiversity Health: A Tasmania-wide assessment of biodiversity health has been completed as part of the Australian Natural Resources Atlas (Audit) Australia-wide Assessment of Biodiversity (Gouldthorpe & Gilfedder 2002). This includes summary reports of each of the nine bioregions in Tasmania. The Northern Midlands received the least favourable assessment, being in a generally degraded condition and declining. The West, Central Highlands and Southern Regions are generally in good condition with static trends, whereas other bioregions were generally in fair condition but declining.

Land Clearance: Land clearance is listed as a threatening process under the Environment Protection and Biodiversity Conservation Act 1999, as native vegetation clearance is a major cause of species and ecological communities being threatened. Since European settlement, an estimated 1,560 million ha of native vegetation are estimated to have been cleared, with >250,000 ha cleared between 1972-99. In recent years the main purpose of native vegetation clearance has shifted from agriculture to conversion to plantation; 44,000 ha of eucalypt plantation and 11,900 ha of softwood plantation were established between 1996 and 2001. In 1999-00 15,820 ha were approved for conversion to plantation or non-forest use, declining to 9,280 ha in 2001-02. Most notable areas of recent land clearance are the Northern Slopes, Northern Midlands, Ben Lomond and Woolnorth bioregions.

Urban Growth: Housing completions have potentially affected 805 ha of priority forest vegetation in Hobart and 291 ha in Launceston between 1992-2002, with uncertainties arising from the unknown proportion of a land parcel being cleared for any housing development. Housing completion data shows where residential development is occurring, but doesn't show accurately the cleared land on each property, so the extent of loss of urban bushland in the State is unknown. Urban growth in Hobart and Launceston are only part of the story, and development along Tasmania's coastlines particularly in the east and northeast is also significant. There is no consolidated information source to determine loss of native vegetation from urban growth at citywide or Statewide scales.

Pollution: Pollutants are discussed in a number of areas of the SoE Report, such as Air Toxics, Industry Discharges to Estuaries, Algal Blooms, Solid Waste, and Disturbance of Acid Sulphate Soils. There is likely to be new information on the effects of pollutants on Tasmania's biodiversity, such as through the Derwent Estuary Program and by the Tasmanian Aquaculture and Fisheries Institute.

Introduced Species: Hundreds of foreign plants and animals have been introduced into Tasmania since European settlement. Naturalised species include 716 vascular plants, 7 non-vascular plants, 31 birds, 17 mammals, 11 fish, 1 reptile, and 952 invertebrates. Many naturalised species are economically beneficial and many are harmless to the environment; however 16% of the naturalised species are significant problems to primary production and/or the natural environment and are known as pests.Out of the 716 vascular plant species 162 are considered to be weeds.

Plant Pests (Weeds) and Diseases: Of the vascular plants, 162 are considered weeds. In 2001 there were at least 64 introduced plant species considered to be key 'environmental weeds' in Tasmania, and 6 of the 20 weeds of national significance were present in Tasmania, including: bridal creeper, boneseed, blackberry, gorse, serrated tussock and willows. In aggregate, one or more of these are found across an extensive range of vegetation communities and land uses. The last five of these are known to be impacting upon 66 already threatened native plant species and 30 threatened and/or bioregionally important vegetation communities. Between 1999 and 2001, 13 new weed alerts were identified of which seven are known to adversely impact biodiversity values and 12 of the 13 are known to affect agricultural production.

Animal Pests: Of the 1,012 naturalised animal species in Tasmania, 44 are considered to be environmental pests, but only six of these are formally declared as pests. Since the 1997 SoE Report, three new recognised animal pests have been recorded in Tasmania: foxes, ferrets and the eastern Gambusia (a type of fish). Foxes in particular have the potential to devastate Tasmania's native mammal and bird populations, including the commercial livestock industry. Tasmania's outer islands serve as safe havens from pests, however 59 of these already have vertebrate pests and only three islands have active pest management programs (Flinders, Macquarie and Bruny). The information on populations and distributions of pest species, and changes over time, is very limited.

Native Forests: The Regional Forest Agreement classifies 50 individual forest communities. There has been a small increase in the percentage of forest harvesting using partial logging (40% in 1994-95 to 49% in 2000-01). Of the commercially valuable forest types, approximately 32% is contained within conservation reserves. Approximately 40% of Tasmania's existing native forest estate as at June 2001 was within formal and informal CAR reserves on crown land or within private CAR reserves. Seven forest communities have less than 15% of their current extent in reserves: six are dry eucalypt communities and one a wet eucalypt community. For all these communities, the majority of the remaining extent is on unreserved private land.

Firewood Collection and Usage: 50% of homes in Tasmania use wood as a primary heat source, and in 1999-00 Tasmania had the highest consumption rate of firewood per household in Australia (610,000 air dry tonnes/yr). Most of the wood is sourced from native forests, and the species favoured for firewood form part of some of the most depleted and poorly reserved plant communities in Tasmania. These most notably are inland peppermint forest, inland black peppermint forest, black peppermint forest on sandstone, and cabbage gum forest and woodland. There is only very limited research into impacts of firewood collection on native habitats.

Native Fauna Harvesting: The species currently harvested in Tasmania are brushtail possums, wallabies (Bennetts and Tasmanian pademelons), shearwaters (muttonbirds), Cape Baron Goose eggs, and freshwater vertebrates most particularly blackfish and short-finned eels.

Native Fauna Control and Culling: A number of native fauna species are relocated, controlled or culled under permit, predominantly to minimise damage to commercial crops and property. Control activities are covered under DPIWE permits issued under the Nature Conservation Act 2002, and examples include permits to: 'shoot to scare only' birds such as eagles and gulls; 'remove and/or destroy' plover nests and/or eggs; 'shoot for crop protection' Cape Barren geese; 'live trapping for release' seal, devil, bird-of-prey etc; and 'poison with 1080 for crop protection' wallaby and brushtail possum. No assessment was able to be made of this issue within the timeframe for preparation of this SoE Report.

Reservation: There are 589 formal reserves covering about 2,606,260 ha of land area (38%) in the State, and about 83,000 ha of the marine environment (3.5%). However, six of the eight terrestrial bioregions in Tasmania have more than 80% of their area outside any type of reserve. The situation is particularly critical in the Northern Midlands where 97.4% of the region is outside any type of public or private reserve.

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