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| Saturday, 01 January 2005 |
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Island woes stark warning for land dwellers by Ed Stoddard PILANESBERG NATIONAL PARK, South Africa, Dec 30 (Reuters) - The extinction of whole species, once specific to isolated islands, is becoming a trend across continents. According to the World Conservation Union, a total of 784 species have become extinct since AD 1500, when accurate historical and scientific records began. While the vast majority of extinctions since that time have occurred on islands, over the past 20 years continental extinctions have become as common. Scientists say that island-style extinctions are creeping onshore because continental habitats are being diced up by human activities- a process that is creating what biologists term "virtual islands." Fences, asphalt, farms and cities - not water - are the boundaries which confine and isolate these man-made islands. "Island biogeography is no longer an offshore enterprise. It has come to the mainlands. It's everywhere," says natural history writer David Quammen in his book "Song of the Dodo: Island Biogeography in an Age of Extinction." "The problem of habitat fragmentation, and of the animal and plant populations left marooned within the various fragments that are untenable for the long term, has begun showing up all over the surface of the planet," he writes. Small island states will be in focus at a United Nations conference next month in Mauritius. Rising sea levels linked to climate change are among the problems facing these countries, many of which are poor and ill-equipped to deal with catastrophe - but their size and isolation present other dangers as well. These dangers are a warning to people living on continents as terrestrial ecosystems become fragmented like islands. Island life is susceptible to extinction for a number of reasons. Isolation and a lack of predators means that many of the bird species which have evolved on them have been flightless. So when people first appeared, these "ecologically naive" creatures - to use the biological jargon - were easy pickings for settlers or sailors in search of fresh protein. The result was that many species were hunted to extinction. Such was the fate of the dodo of conference host Mauritius. A limited gene pool can be another consequence. And small territories are especially vulnerable to disease or sudden natural disasters, such as the tsunamis that washed over much of Asia on Sunday. These trends are now appearing on mainland territory. Take the virtual island managed by Mandy Momberg. The park ecologist for South Africa's Pilanesberg National Park, she is responsible for 50,000 hectares (123,600 acres) of recovering wilderness surrounded by high-voltage electric fencing. "Pilanesberg is an island ... and attempting to manage the ecology here is always a learning experience," she said. At first glance, it looks like a conservation success story. Proclaimed in 1979, more than 50 species of large wild mammals native to the region - including the so-called "Big 5", elephant, rhino, buffalo, lion and leopard - now roam on land once used for cattle farming and citrus orchards. Set in rugged hills on the site of an ancient volcano 150 km (90 miles) northwest of Johannesburg, it has 354 species of birds, 65 different kinds of reptiles and 18 amphibians. "At last count we had 172 elephants. The thumbsuck is that 100 elephants is the carrying capacity. Culling is an option we might have to consider," said Momberg. "There are very few big trees here because of the elephants. They are changing the landscape into an open savannah system." Although small islands often have a dearth of large predators, Pilanesberg is full of them, including wild dogs, cheetahs and brown hyenas, not to mention the very big cats. "We've got too many predators here," Momberg said. "The wild dogs need more room. They have been running their prey into the fence and appear to have a 100 percent kill rate on hunts." Other "island-like" characteristics have cropped up in the fragments that constitute South Africa's many game farms, where antelope species are often raised without exposure to predators. Like their counterparts on islands that lack big meat-eaters, they have become ecologically naive. "We were concerned about too much predation so we brought in about 600 new animals, different antelopes, bought from game farms. Some of them walked right up to the predators like the lions because they were curious," she said. The results, of course, were fatal. At least Pilanesberg's ecosystem can be monitored and managed and there are plans to link it with other parks via corridors, which will remove many of the current pressures. Other animals stuck on "man-made" islands may not be so lucky and we can only guess at what the long-term impact of places like Pilanesberg will have on wild populations. In her novel "Malaria", Susan Hillmore depicts the slaughter of the planet's last herd of wild elephants on an Asian island, a former oasis turned to ruin. The last wild elephants may well find themselves confined to an island but it is more likely to be a "virtual" one on a continent rather than Hillmore's fictionalised dystopia at sea. And such confinement may well signal their doom. |
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