More than 8,300 offshore islands occur around Australia and within our external territories. These islands cover the full range of environments, from tropical to sub-Antarctic and range in size from tiny rocks and cays to extremely large land masses. For example, Bramble Cay in the Torres Strait has a circumference of only around 700 m while Melville Island in the Northern Territory covers 578,577 ha.
Offshore islands provide breeding sites and important refugia for many threatened species. They also have their own endemic species and sub species such as the Lord Howe Island currawong (Strepera graculina crissalis) and the Bramble Cay melomys (Melomys rubicola). Some offshore islands provide a last refuge for species that are extinct or critically threatened on the mainland. These island populations can help facilitate fauna recovery programs on the mainland and/or other islands by providing founder stock for translocation. For these reasons, islands provide a wonderful opportunity to protect and recover our native biodiversity.
However, vertebrate pests have been introduced to, or have successfully invaded many of Australia's offshore islands. These feral animals threaten many important island species. Some key pests such as rats have been listed as key threatening processes under the Environment Protection and Biodiversity Conservation Act 1999.
The Australian Government is assisting the states and territories to manage the islands under their jurisdiction through identifying feral animals on offshore islands, prioritising islands for biodiversity conservation, and linking people and projects together.
Many commendable pest management plans have already been implemented on islands (e.g. black rats have been eradicated from Lord Howe Island, NSW and feral cats from Macquarie Island, TAS).
The Australian Government has initiated the IslandNet offshore islands network to help facilitate the conservation management of Australia's offshore islands. The objective of IslandNet is to assist in the sharing of knowledge between people involved in island conservation issues.
IslandNet provides a comprehensive information base of experience and expertise. From this, participants can find out who is doing what and where, what programs have been undertaken and the lessons that have been learnt. IslandNet publishes a quarterly newsletter with details of recent research and up-coming meetings relevant to offshore islands.
The Invasive Animals Cooperative Research Centre, which host IslandNet, maintains an email list of those people and organisations in Australia and the region that have an involvement, or interest, in island conservation issues. This includes researchers, field officers, government employees, consultants, companies with commercial interests, and Indigenous and island community representatives.
Prioritisation of high conservation status offshore islands
With approximately 8,300 offshore islands, the Australian and state and territory governments need to prioritise funds for conservation management to those islands where conservation benefits and eradication potential is greatest.
In 2009 the Department contracted an independent assessment of the conservation status of Australia's offshore islands, using the Australian Government's databases of feral animals, islands biodiversity data, threatened species distribution data, seabird breeding locations, and vegetation data. The resulting report, Prioritisation of high conservation status offshore islands, provides a priority list of 100 islands of high conservation status (greater than 200 ha in size) to help guide this prioritisation of funds.
Threat abatement plan for exotic rodents on islands
In 2006 the Australian Government listed exotic rodents on islands as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and developed a threat abatement plan for rats and mice on islands less than 100 000 ha in area.
This plan, completed in 2009, is available at: www.environment.gov.au/biodiversity/threatened/publications/tap/exotic-rodents.html
The objectives of the Plan are to:
- eradicate exotic rodents from high-priority islands
- mitigate the impacts of exotic rodents on biodiversity values on high-priority islands where they cannot be eradicated, and
- prevent the invasion of islands currently free of exotic rodents.