Good intentions have rarely gone so awry. When conservationists tried to save an island鈥檚 birds by culling its feral cat population, they overlooked one critical consequence: rabbits. A new study reveals that removing just 160 feral cats triggered a boom in Macquarie Island鈥檚 rabbit population from about 4000 in the year 2000 to 130,000 in 2006.
The cats were shot as they had been preying on the island鈥檚 burrowing birds. But the newly rampant rabbits have devastated vegetation over 40% of the island. Clearing up the mess is expected to cost at least $16 million, and it remains unclear whether the island will ever fully recover. (See a .) A landslip in 2006 that badly damaged a penguin colony has been blamed on rabbit destruction of the vegetation.
A World Heritage Site halfway between Australia and the Antarctic, the Macquarie Island case is a tragic demonstration of why agencies in charge of conservation need to analyse all aspects of an eradication programme. 鈥淲e need a culture change,鈥� says of the University of Queensland in Brisbane, Australia. 鈥淚t鈥檚 a generalisation, but people who do environmental work are often adverse to mathematics, and so avoid quantitative risk assessments.鈥�
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Running wild
The (TPWS) eradicated the cats to protect native birds, such as the sooty albatross, believing that the continued release of myxomatosis virus would limit the expected increase in rabbits.
However, according to study leader Dana Bergstrom of the in Tasmania, had they done their calculations they would have spotted the risk of a population explosion and may have been able to avoid it. Several species of albatross nest on coastal slopes that are being denuded by rabbits.
Mathematics-based risk-assessment tools for environmental interventions have been available for decades, but they are not universally used outside of academia. On Macquarie, the consequences of failing to conduct a risk assessment have been particularly obvious because its simple, cold-climate island ecosystem meant that the ecological damage was not camouflaged by myriad more subtle changes, says of the University of Melbourne, Australia.
Despite the devastation, a TPWS told 快猫短视频 that eradicating the feral cats was a 鈥渕ajor conservation achievement鈥�. They are now to start in 2010, and say this time they will conduct a quantitative risk assessment first.
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