How removing cats devastated a World Heritage island in Australia

January 13th, 2009 - 4:09 pm ICT by ANI  

Washington, Jan 13 (ANI): Ecologists have revealed that removing cats, which were considered an invasive species in the sub-Antarctic Macquarie Island in Australia, a World Heritage Site, has caused environmental devastation that will cost more than 24 million dollars (Australian) to remedy.

Using population data, plot-scale vegetation analyses and satellite imagery, the ecologists from the Australian Antarctic Division (AAD), the University of Tasmania, Blatant Fabrications Pty Ltd and Stellenbosch University found that after cats were eradicated from Macquarie in 2000, the islands rabbit population increased so much that its vegetation has been devastated.

According to the studys lead author, Dr Dana Bergstrom of the Australian Antarctic Division, Satellite images show substantial island-wide rabbit-induced vegetation change. By 2007, impacts on some protected valleys and slopes had become acute.

We estimate that nearly 40 percent of the whole island area had changed, with almost 20 percent having moderate to severe change, she added.

Rabbits were introduced to Macquarie Island in 1878 by sealing gangs.

After reaching large numbers, the rabbits became the main prey of cats, which had been introduced 60 years earlier.

Because the rabbits were causing catastrophic damage to the islands vegetation, Myxomatosis and the European rabbit flea (which spreads the Myxoma virus) were introduced in 1968.

As a result, rabbit numbers fell from a peak of 130,000 in 1978 to less than 20,000 in the 1980s and vegetation recovered.

However, with fewer rabbits as food, the cats began to eat the islands native burrowing birds, so a cat eradication programme began in 1985.

Since the last cat was killed in 2000, Myxomatosis failed to keep rabbit numbers in check, and their numbers bounced back and in little over six years, with rabbits substantially altering large areas of the island.

According to Bergstrom, Increased rabbit herbivory has caused substantial damage at both local and landscape scales including changes from complex vegetation communities, to short, grazed lawns or bare ground.

Our study shows that between 2000 and 2007 there has been widespread ecosystem devastation and decades of conservation effort compromised, he added.

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. On Macquarie Island, this cost will be around 24 million dollars (Australian), he further added. (ANI)

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