Image from Sara Golemon
Chalk up another one for human "ingenuity." Efforts to reverse the proliferation of invasive species on Macquarie Island, a 50-square mile piece of land located approximately halfway between Australia and Antarctica, have taken a disastrous turn for the worse--with the likely end scenario a complete "ecosystem meltdown." The sole last resort, scientists now believe, is a massive $16 million rescue plan, reports the LAT's Thomas H. Maugh II.
Image from peterastn
Macquarie Island, which was named a World Heritage Site in 1997 (for being the only location in the world with mantle rocks actively exposed above sea level), has a long and difficult ecological history. Shortly after being discovered in 1810, humans introduced the first of what would become many invasive species to the island: rats and mice that had accompanied the sailors on their ships.
Their first attempt to fight back this wave of invasive rodents consisted of introducing cats in 1818. This had the desired effect in the short term, slashing the number of mice and rats. Yet, with a lack of natural predators, the number of feral cats quickly mushroomed as well. The situation only got worse a few decades later when the sailors decided to bring rabbits to the island to provide a reliable source of food.
The numbers of both species soon grew out of control, resulting in the annihilation of two native bird species and the stripping of Macquarie Island's vegetation. In another poor attempt at taming the situation, scientists set the Myxoma virus (which spreads a disease called myxomatosis that is lethal to rabbits) upon an unsuspecting rabbit population, with brutally effective results.
While the strategy helped drastically reduce the number of rabbits (those that survived may have developed a natural resistance to the disease), it also cut into a vital supply of food for the feral cat population. As a result, the cats started eating other bird species, quickly putting their existence at risk, which again prompted the scientists to intervene--launching a campaign of extermination that succeeded in removing all of them by 2000. (In total, the cats caused about 60,000 seabird deaths per year since the time they were introduced.)
But that wasn't quite the end of the story, as Maugh writes:
But to the researchers' great surprise, biologist Dana Bergstrom of the Australian Antarctic Division and her colleagues report in the current Journal of Applied Ecology, the rabbits began proliferating again despite the presence of the virus. The animals have now stripped as much as 40% of the island bare of vegetation. They were even blamed for a 2006 landslide that wiped out part of a penguin colony.
(ABC News Online covered this story last year.)
The elimination of the cats also allowed the once depleted rat and mice population to gain ground, causing another wave of wildlife and plant destruction. The $16 million "rescue" plan (rescue from what, one might ask) could take up to 7 years, and, given the scientists' track record, there is no guarantee of success.
More often than not, there are no good outcomes to these problems. The only foolproof solution, it seems, is also the most obvious one: Don't introduce new species to unfamiliar habitats in the first place.