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FEATURE - Is a "sixth" extinction looming?

Date: 23-Jul-02
Country: SOUTH AFRICA
Author: Ed Stoddard

But the real danger to these elusive birds, which resemble colourful sentinels with their striking red beaks and legs set against glossy black feathers, is not the razor-sharp teeth of the crocodiles who lie just a few metres (yards) away.

It is the teeth of chainsaws thousands of miles to the north, where old growth forests - habitat vital to the bird's survival - are being mowed down.

The black stork is one of many species which scientists fear could follow the dinosaurs down the road to extinction because of human activities such as logging, farming and building dams.

Many credible scientists fear that the sixth mass extinction in the planet's long history is unfolding - a doomsday scenario dismissed as alarmist by some.

A recent U.N. report, prepared ahead of a summit next month in Johannesburg on the environment and poverty, warned that 12 percent, or 1,183 bird species, and 1,130, or nearly a quarter of all mammal species, are regarded as globally threatened.

A SIXTH EXTINCTION?

Mass extinctions have occurred five times in the four billion year history of life.

They are loosely defined as moments in geological history when half or more of all marine species - which today are preserved in fossils - die off in a short period of time. (Terrestrial life is also not believed to fare well during these periods).

According to one book on the subject, "The Sixth Extinction", by Richard Leakey and Roger Lewin, the grim reaper first visited Earth on this vast scale 450 million years ago.

The second mass extinction took place 100 million years later, giving rise to coal forests. In the Triassic period 250 and 200 million years ago, two mass extinctions snuffed out countless species.

Then, 65 million years ago, scientists believe the dinosaurs were killed off when a giant meteorite collided with Earth.

Scientists say the sixth extinction will have been brought about entirely by people.

"In the next 50 to 100 years there is a good possibility that there could be a mass extinction of species which is human-induced," said Dr Susan Lieberman, director of the Species Programme for the World Wide Fund for Nature (WWF).

"We are heading for a crisis. And we have to act now if we are going to avert this," she told Reuters.

Leakey and Lewin estimate that perhaps 50 percent of all species will become extinct in the next 100 years. Others take a more measured view but agree that a crisis is looming.

Bjorn Lomborg argues in his controversial recent book, "The Sceptical Environmentalist", that we could lose about 0.7 percent of the planet's species over the next five decades - an estimate far below many but one which he says is "not trivial."

Most scientists concede that the number of recorded extinctions to date is far less than the "so many lost each day" estimates cited in the more alarmist literature.

The Committee on Recently Extinct Organisms says at least 70 species of fish, birds and mammals have disappeared since 1970.

The WWF says 81 freshwater species of fish are recorded to have become extinct in the last 100 years. The majority, 50, were endemic to Africa's Lake Victoria and vanished because of the introduction there of the voracious Nile perch.

Biologists say that countless species which have never been discovered - notably in tropical rain forests and marine ecosystems - have probably become extinct already.

BLACK STORKS AND WILD DOGS

The black stork and wild dog, two species in Kruger which nobody disputes are endangered, sum up the threats to many.

The black stork's global population is about 7,000 to 9,500 nesting pairs, according to Latvian ornithologist Maris Strazds.

The biggest population, about 4,500 to 6,000, is found in Europe, mostly in Poland, Belarus and Latvia.

Unlike their more gregarious and numerous cousin the white stork, which often nests on farmhouses in Eastern Europe, the shy and reclusive black stork prefers to decamp far from the

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