A programme to eradicate cats in order to save birds on the remote Macquarie Island in the Southern Ocean has resulted in an explosion in rabbit numbers and destruction of native plantlife, scientists have warned.
Louise Gray, The Telegraph 11 Jan 09;
Cats were removed by conservationists from the sub-Antarctic island from the 1980s in order to save native burrowing birds.
But a new report has found the resulting problem with rabbits has caused damage to plantlife that will cost £11 million to repair.
The scientists are now warning that measures to control invasive species, such as the programmes to control hedgehogs, rats and grey squirrels in the UK, must carefully consider the effect on other species.
Finch Creek on sub-Antartic Macquarie Island. Rabbits have stripped 40% of the island bare of vegetation, scientists say. Photograph: /Australian Antarctic Division
Cats were brought to Macquarie Island by sailors in the 19th Century, where they lived off rabbits that were also introduced.
But after the virus myxomatosis wiped out the rabbit population in the 1970s, the cats turned to killing native burrowing birds on the island.
Conservationists intervened with a cat eradication programme in the late 1980s to save the endangered bird species on the World Heritage Island.
However a new study by the University of Tasmania and Stellenbosch University found this has led to an explosion in the rabbit population, which is killing native plantlife and will cost more than £11 (A$24) million to repair.
A report in the British Ecological Society's Journal of Applied Ecology warns conservation agencies worldwide must learn important lessons from what happened on Macquarie Island, which lies around halfway between Australia and the Antarctic continent.
Dr Dana Bergstrom of the Australian Antarctic Division, one of the authors of the study, said conservation agencies must learn from the experiences on the island to balance the affects of removing alien species.
She said: "Our study shows that between 2000 and 2007 there has been widespread ecosystem devastation and decades of conservation effort compromised. The lessons for conservation agencies globally is that interventions should be comprehensive, and include risk assessments to explicitly consider and plan for indirect effects, or face substantial subsequent costs."
Macquarie Island faces 'ecosystem meltdown' after conservation efforts backfire
Attempts by conservationists to eradicate cats in order to save birds on the sub-Antarctic island has caused an explosion in the rabbit population and damage to plantlife that will cost £11m to repair, scientists say
David Adam, guardian.co.uk 12 Jan 09;
It is a cautionary tale of recklessness, good intentions and the ecological mayhem that can result when people interfere with the delicate balance of Mother Nature: scientists today catalogued the unfortunate series of biological events caused by human meddling and alien species that has devastated the once pristine sub-Antarctic Macquarie Island.
Lessons must be learnt on all sides, the scientists say, because well-intentioned attempts by conservation experts to fix the island have so far made the situation worse. Life across almost half the island, a World Heritage site, has been affected, and experts are now weighing up a £11m rescue plan.
Dana Bergstrom, of the Australian Antarctic Division said: "The big lesson is to question all assumptions made in managing and removing alien species from special areas, because there could be unintended consequences."
Things began to go wrong on Macquarie Island, halfway between Australia and Antarctica, soon after it was discovered in 1810. The island's fur seals, elephant seals and penguins were killed for fur and blubber, but it was the rats and mice that jumped from the sealing ships that started the problem. Cats were quickly introduced to keep the rodents from precious food stores. Rabbits followed some 60 years later, as part of a tradition to leave the animals on islands to give shipwrecked sailors something to eat.
Given easy prey, cats feasted on the hapless rabbits and feline numbers quickly grew. The island then lost two endemic flightless birds, a rail and a parakeet. Meanwhile, the rabbits bred rapidly and nibbled the island's precious vegetation.
By the 1970s, some 130,000 rabbits were causing so much damage that the notorious disease myxomatosis was the latest foreign body introduced to Macquarie, which took the rabbit population down to under 20,000 within a decade.
"The island's vegetation then began to recover," Bergstrom says.
But what was good for the vegetation proved bad for the island's wildlife. With fewer rabbits around, the established cats turned instead to local burrowing birds. By 1985, conservationists deemed it necessary to shoot the cats.
The last cat was killed in 2000, but the conservationists were horrified to see rabbit populations soar. Myxomatosis failed to keep numbers down, and the newly strong rabbit population quickly reversed decades of vegetation recovery. In 2006, the resurgent rabbits were even blamed for a massive landslip that wiped out much of an important penguin colony.
Writing in the Journal of Applied Ecology, Bergstrom's team describes how the rabbits have now stripped some 40% of the island bare. "When rabbits first move into coastal areas, the lush slopes are often turned into bare earth," she says. "Often a weed grass called Poa annua establishes, and the bare areas then turn into what looks like nicely mowed golf courses, mowed by rabbits."
The scientists say the chain of events at Macquarie is a rare example of a "trophic cascade", the knock-on effects of changes in one species abundance. The next stage could be an "ecosystem meltdown".
The Tasmanian Parks and Wildlife Service intends to fix the island once and for all, and has drawn up plans to eradicate all 130,000 rabbits, along with the estimated 36,000 rats and 103,000 mice that live there.
The move could yet provoke more unexpected side effects, Bergstrom says. "This is the largest island on which this type of eradication program will have been attempted."
Removing species from sub-Antarctic island 'caused disaster'
Yahoo News 12 Jan 09;
PARIS (AFP) – Efforts to remove an invasive species from a sub-Antarctic island that has been named a World Heritage site accidentally triggered an environmental catastrophe, a study to be published on Tuesday says.
The eradication programme on Macquarie Island, lying halfway between Australia and Antarctica, is a cautionary tale about the complex web of ecosystems, its authors say.
In the early 19th century, cats were introduced to Macquarie Island, where they swiftly became feral.
In 1878, rabbits were brought in by seal hunters, according to the paper, which appears on Tuesday in the Journal of Applied Ecology, published by the British Ecological Society.
By the late 1960s, the rabbit population had become so large, and so destructive of vegetation, that the Australian authorities used the Myxoma virus -- which causes the disease myxamotosis among rabbits -- to control their numbers.
As a result, the rabbits dwindled, from a peak of 130,000 in 1978 to 20,000 in the 1980s, and the vegetation recovered.
The downside: the cats, which had been tucking into the rabbits for food, turned to Macquarie's native burrowing birds for sustenance.
Fearing that the birds would get wiped out, the authorities returned to the island in 1985 to launch a cat eradication programme.
The cats were all killed in 2000, but myxamotosis had failed to do the same to the rabbits. Without their feline predators, the rabbit population surged anew and in just half a dozen years has inflicted enormous damage, in some places stripping the ground bare.
In ecologists' terms, this is an example of "trophic cascades" -- when a species' abundance is significantly reduced or increased, the change resonates along the food chain.
"Between 2000 and 2007 there has been widespread ecosystem devastation and decades of conservation effort compromised," said lead author Dana Bergstrom of the Australian Antarctic Division.
"The lessons for conservation agencies globally is that interventions should be comprehensive, and include risk assessments to explicitly consider and plan for indirect effects, or face substantial subsequent costs."
To fix the problems on Macquarie Island will cost around 24 million Australian dollars (17 million dollars, 12.6 million euros), the authors estimate.
Macquarie is a long, narrow island 34 kilometres (21.25 miles) long by five kms (3.1 miles) wide with tundra-like vegetation that grows in its cool, maritime climate, as well as large numbers of birds, seals and penguins. The island was declared a wildlife sanctuary in 1933.
It was named a World Heritage Site in 1997 because it is geologically unique: it is the only place where rocks from Earth's mantle, some six kilometers (3.75 miles) below the ocean floor, are directly exposed above sea level.
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