THE SIXTH EXTINCTION

Press, 9 December 1988, Page 13

THE SIXTH EXTINCTION

DONALD FREDERICK,

, Of

the National Geographic News Service, writes from Washington, D.C.

Mass extinction: The phrase brings images of the widespread dying of animals and plants millions of years ago.

The world has been hit with five major extinctions, and scientists say that a sixth is well under way.

Unlike earlier catastrophes, caused by longterm evolutionary competition or environmental change, this one is caused by man. “We have become the greatest catastrophic agent since the extinction spasm that closed the Mesozoic Era 65 million years ago,” says Edward O. Wilson, a Harvard University biology professor. Hardest hit by the new wave of extinction are the world’s tropical forests. About a third of Earth’s plant and animal species are believed to live in them.

“In a few square kilometres in Ecuador or Malaysia,” says Wilson, “can be found hundreds of species of birds, thousands of species of plants, and tens of thousands of species of beetles.”

Denuded by farming, ranching, logging, mining, and the demand for firewood, the forests are fast disappearing. “Although the large and sparsely populated blocks of forest in the Brazilian Amazon and

in the interior of Guiana might last past the middle of the next century, most of the remaining forests will be gone within the next 25 years,” says Peter H. Raven, director of the Missouri Botanical Garden and an expert on tropical forests. With the forests will go irreplaceable sources of medicines and germ plasm important to agriculture, as well as much of the world’s most remarkable wildlife, including animals such as the orangutan, tapir, and spider monkey, says Raven. “Many plant and animal species in the forests might become extinct before they can even be discovered or described by scientists,” he says. “Over the next 25 years, we can expect the rate of extinction to average approximately 100 species a day, with the rate increasing steadily over this period of time.”