The extinction of whole species, once specific to isolated islands, is becoming a trend across continents
Aozotorp
headline:
SOUTH AFRICA: December 31, 2004
PILANESBERG NATIONAL PARK, South Africa - 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.
VULNERABLE TO EXTINCTION
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.
MAN-MADE ISLANDS
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. ... (cont)