Dead zones in the oceans and a rate of extinction 1,000 times faster than evolution

Humans have created at least 50 dead zones in the sea with little or no oxygen - and altered almost half of the land surface of the planet.

We are extinguishing other species at 1,000 times the natural rate seen in evolution. In the next century, this massacre could increase to 10,000 times, the International Botanical Congress at St Louis, Missouri was told yesterday

Peter Raven, director of the Missouri botanical gardens, said that, at this rate, one third to two thirds of all species of plants, animals and other organisms would be lost during the second half of the next century, a loss on a scale not seen since the destruction of the dinosaurs 65m years ago.

The problem, according to Prof Raven, is that we cannot even know which species are being lost. There could be between 7m and 10m species of plants and animals but only about 1.6m have been identified. Some 250,000-300,000 plants had been recorded as herbarium specimens, leaving some 50,000 unknown.

Many species of plants and animals were being extinguished before they could be described, if only because 80% of biologists live in the industrialised countries, which are home to only about 20% of the world's species.

He outlined a seven-point programme to slow the extinction rates of the world's plants, by establishing an international body, investing in museums and herbariums, studying the ways in which species are threatened, conserving medicinal plants, educating the public and funding research.

"Our great grandchildren may live in a world in which more than half the plant species that exist now will be known only as specimens," he said.

Jane Lubchenko, a zoologist at Oregon State university, told the 4,000 scientists at the congress of "a disturbing negative trend in the earth's ability to maintain the quality of human life":

• By filling in wetlands, turning prairies to cornfields, or converting forests to cities, humans had transformed close to 50% of the land surface.

• The excessive use of fertiliser and the wanton burning of fossil fuel had doubled the amount of nitrogen in the environment.

• Extinction rates were 100 to 1,000 times what they would have been without human-induced changes.

• Last year was the hottest year ever recorded, because of the human release of carbon dioxide and other greenhouse gases in the atmosphere.

She said there were 50 "dead zones" with little or no oxygen in the world's coastal areas. The largest in the western hemisphere was caused by pollution from the Mississippi flowing into the Gulf of Mexico.

"We're witnessing many signals of the problems that will result from these changes, including toxic algal blooms, coral bleaching and sudden disappearance of fish from key fisheries," she said.

Half of the world's mangrove forests had been lost to coastal development or fish farming - which now accounted for more than one quarter of all the fish consumed. But it took two or three pounds of fish to grow one pound of farmed seafood and this took food away from wild fish, birds and marine mammals.

Around 3,000 species of marine creatures were being carried around the planet in the ballast tanks of ships - resulting in serious invasions which threatened native species. All of these changes could disrupt the planet's ability to provide food, building materials, clothing and medicines for its 6bn people.

"We need to take stock of these massive changes, understand their implications and change our direction," she said. "We are currently inattentive stewards. It is in our best interests to be more fully engaged in ensuring our own health, prosperity and well-being."



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