Prioritisation of high conservation status mainland islands

Eco Logical Australia, 2009

Eco Logical Australia Pty Ltd for the Department of the Environment, Water, Heritage and the Arts, 1 July 2009

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Top 50 ranked high conservation status mainland islands in alphabetical order:

Executive summary

Introduced vertebrate species have colonised large areas of mainland Australia and cause severe environmental damage, particularly in areas of high conservation value. Managing the threat posed by invasive pests is a high priority of the Australian Government. Several Australian Government Threat Abatement Plans identify the need to prevent invasive species from “occupying new areas in Australia and to eradicate feral animals from high-conservation-value ‘islands’”. ‘Islands’ are defined as both offshore islands and as mainland islands that are isolated and/or do not currently have invasive species.

The Department of the Environment, Water, Heritage and the Arts (DEWHA) engaged Eco Logical Australia (ELA) to identify high conservation value “mainland islands” and prioritise them according to risk from vertebrate pest species. An analysis of the management regimes in place for the highest priority islands was also required.

Currently, there is no agreed definition of what constitutes a mainland island and consequently, there is no central database of the location of high conservation value “mainland islands”. Therefore the first step of this project was to define and identify the location of high conservation value mainland islands. The definition of mainland islands was developed collaboratively by DEWHA and ELA and was based on twelve biodiversity and conservation criteria. Analyses were based on existing datasets that were available and consistent at a national level.

In total, 471 mainland islands were identified. Islands were found in all states and territories, however, they were primarily located along the east coast (over 80% of islands were in NSW, Qld and Victoria). The main factor driving the location of mainland islands was the combination of high species richness and high endemism. Factors including threatened species/communities and World Heritage Areas were also influential.

Mainland islands were prioritised based on an assessment of their overall conservation value and level of threat, particularly threats from vertebrate pests. High conservation value islands were located across Australia, while threats were concentrated along the eastern seaboard. Consequently, the top 100 highest priority islands were concentrated along the east coast of Australia. Other top 100 islands located away from the east coast include Shark Bay and Stirling Range National Park (WA), Kakadu and the MacDonnell Ranges (NT), the Coorong (SA) and the Tasmanian Wilderness.

Management of vertebrate pests in Australia is undertaken by all levels of government as well as private land-holders and managers. Consequently, management of pests on mainland islands falls within a sometimes complicated array of tenures. Pest management on mainland islands can be categorised in one of three ways: islands covered entirely by one specific management arrangement; islands not covered by specific management arrangements and islands covered by a combination of management arrangements.

There were several limitations associated with each stage of this project. The definition of mainland islands was restricted by nation-wide consistency of data, data biases and resolution, delineating boundaries and the overall availability of relevant datasets. The results of the prioritisation analysis should be interpreted with care, as the occurrences and impacts of pests used in the analysis are potential rather than actual. Finally, consideration of management regimes for mainland islands was based on publically available information only. Overall, much information about pest management in Australia is diffuse and difficult to access, and consequently it is hard to gauge the degree to which pest management has occurred / is occurring at many sites around Australia.

Several recommendations stem from this project. Overall, it is recommended that the outputs of this study be used as a strategic guide rather than a definitive list of areas requiring significant pest management. Additional recommendations are provided with respect to pest management, this and future studies and data resources.

See also