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    Threatening Processes

        At a glance

        Tasmanian cave spider

        The issue

        Tasmania is well endowed with unique animals and plants of which many are endemic to the State. Some endemic species have evolved in Tasmania while others were once more widespread but are now restricted to Tasmania. Tasmania retains the most ecologically diverse group of large marsupial carnivores, the largest tracts of cool temperate rainforest in Australia and its cave fauna is amongst the most species-rich in temperate Australia. Tasmania also has many remnants of native grasslands, which are home to a multitude of native plants and animals.

        All of these special biodiversity features are under pressure from human impacts caused by inappropriate land use practices, introduced pests and diseases.

        This 'At a glance' section provides a summary of the review of Tasmania's special biodiversity features. More detailed information and references are contained in the Special Features Issue Report.

        Several recommendations are presented that seek to address some of the needs of Tasmania's special features.

        Favourable news

        • A Recovery Plan for Tasmanian Native Grasslands was adopted by the Commonwealth in 1999. The main objectives of the recovery plan aim to control the clearance of native grasslands, protect and enhance threatened species and biodiversity, purchase a significant grassland property in the Tasmanian Midlands, and to negotiate conservation agreements with landowners (Barker 1999).
        • The reservation of a number of rainforest community types has been improved by the Regional Forest Agreement (RFA), namely the King Billy Pine, Huon Pine, Pencil Pine, Callidendrous and Thamnic rainforest communities (RPDC 2002).
        • The Tasmanian Government has established a Fox Free Taskforce to implement a long-term eradication program and to ensure foxes are never introduced to Tasmania again. A range of methods are currently being applied with others being trialed.
        • The Tasmanian Government has so far allocated $40,000 to study the Tasmanian Devil virus and identify its cause.
        • The Mole Creek Karst National Park Draft Management Plan was completed in 2001. The plan establishes a number of objectives, policies and actions for the conservation of cave fauna.

        Unfavourable news

        • The Recovery Plan for Tasmanian Native Grasslands identifies six major threatening processes that affect native grassland in Tasmania. The major threats include: clearance of native vegetation; dam building; pasture improvement and fertilisation; persistent overgrazing; exclusion of infrequent fire and light grazing causing the invasion of shrubs and trees; and residential development.
        • Only 1,289ha of grassland and grassy woodland are reserved in the National Reserve System, constituting only 1.2% of their total area (State Biodiversity Committee 2002). It is estimated that lowland and highland grasslands are being cleared at a rate 1.27% and 0.2% pa respectively (Barker 1999).
        • Most native grasslands occur in road reserves, and unfortunately many main road management protocols have failed, leading to the destruction of significant native grassland remnants (Barker 1999).
        • Deliberate or accidental burning has caused over 7% of Tasmania's temperate rainforest to be damaged by fire in the last century. One-third of the State's King Billy pines have been destroyed as a consequence (DPIWE 2001).
        • Mature myrtle trees are susceptible to death from myrtle wilt caused by the fungus Chalara australis (Kile & Walker 1987). Disturbances to rainforest stands, such as logging or thinning treatments, increase mortality due to myrtle wilt (Packham 1991).
        • Thirty-nine rainforest species are known to be susceptible to Phytophthora infection. Fifteen of these are threatened species including six that are endemic to Tasmania (State Biodiversity Committee 2002).
        • In 2000, an estimated 12-20 foxes were deliberately introduced into Tasmania (DPIWE 2002). If foxes become established in Tasmania, 78 native vertebrate species could be at risk. Thirty-four of these have locally restricted ranges, 16 are suspected to be already declining in distribution and 12 are listed in Commonwealth and State threatened species legislation (DPIWE 2002).
        • A retrovirus is attacking the Tasmanian Devil causing cancerous lesions on the face, softening of the skull and eventual death. In high-density populations, over 90% of adults succumb to the virus (DPIWE 2003). The decline in devil populations has the potential to provide a window of opportunity for the establishment of foxes in the State.
        • The Mole Creek Karst National Park Draft Management Plan identifies three major impacts to cave systems and cave fauna. These include hydrological impacts caused by inappropriate upstream land use practices, atmospheric impacts caused by inappropriate development in caves, and visitor impacts.

        Uncertain news

        • Little is known about the retrovirus affecting the Tasmanian Devil and its causes.
        • It is uncertain what effect a decline in Tasmanian Devil populations may have on the establishment of the fox. It is thought that the Tasmanian Devil may be acting as a buffer to the establishment of foxes in Tasmania through competition for food.
        • Vegetation change for some vegetation communities (e.g. grasslands) is not well understood and it is difficult to monitor currently using remote sensing techniques.

        Remnant rainforest vegetation

        Remnant native grasslands

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        Last Modified: 14 Dec 2006
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