"Is a 'Sixth' Extinction Looming?"

BY ED STODDARD
Reuters

"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 Program 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."

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