Lessons learned from devastating effects of cat eradication on Macquarie Island

Vegetation along Finch Creek, Macquarie Island in 2001 showing the tall lush native plant community, mostly unmodified by rabbit grazing.
Vegetation along Finch Creek, Macquarie Island in 2001 showing the tall lush native plant community, mostly unmodified by rabbit grazing. (Photo: Kate Kiefer)
Vegetation along Finch Creek, Macquarie IslandTasmanian Department of Primary Industries and Water (DPIW) exclusion area used for monitoring the effects of rabbit grazing. The vegetation within the enclosure is indicative of what would cover this area if rabbits were absent; the vegetation outside thRabbit warren commonly seen on the drier slopes of Macquarie Island. The presence of high numbers of rabbits in these areas has not only resulted in major soil disturbance through burrowing, but also complete modification of the vegetation through grazingThis image illustrates the extent of the destruction of native tall tussock grassland vegetation along the coastal fringes of  Macquarie Island

13 January 2009

Research by Australian Antarctic Division scientists published today in the British Ecological Society’s Journal of Applied Ecology has used World Heritage-listed Macquarie Island as an example to illustrate the importance of taking a comprehensive approach to management of invasive species in natural environments.

Decades of conservation effort was compromised on Macquarie Island when a feral cat eradication program from 1985 to 2000 led to unintended and unplanned consequences.

Terrestrial ecologist Dr Dana Bergstrom said that the program, while well-intentioned, resulted in widespread ecosystem devastation when cats were eradicated and rabbit numbers exploded.

“Cats were introduced to Macquarie Island in about 1820 and rabbits about 60 years later in 1878. By 1960, grazing by rabbits was having very destructive effects on the native vegetation,” said Dr Bergstrom.

“Management of rabbits commenced in 1968 with the introduction of the European rabbit flea (vector of the Myxoma virus) followed in 1978 by release of the Myxoma virus. Rabbit numbers peaked at 130,000 in 1978 but eventually dropped to about 20,000 and within 8–10 years the island vegetation had recovered substantially.

“With fewer rabbits to prey on, the cats switched to native seabirds and by the mid 1980s were having significant detrimental impacts on seabird populations. Cat eradication commenced in 1985 and the last cat was killed in 2000. Since then rabbit numbers have increased rapidly and have substantially altered large areas of island vegetation,” she said.

Using Macquarie Island as an example the paper suggests that the nature of conservation funding, which typically limits agencies to step-by-step eradication programmes rather than more comprehensive approaches, is often a problem. Funding of larger but more holistic conservation measures, as opposed to smaller, stepwise measures may, in the long run be more successful and cost effective.

A new strategy for Macquarie Island is currently underway to eradicate rabbits, mice and rats simultaneously at a cost of approximately $24 million to be met equally by the Australian and Tasmanian governments.

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