Entitled "Living Planet Report 2002", it said there was so much pressure on water supplies, forests, usable land and energy sources that within 150 years the planet could be exhausted.

At current exploitation rates and population trends, over 20 percent more natural resources were being used up every year than could be regenerated, meaning that by 2050 two Earths would be needed to meet present resource demands.

"Natural resource consumption can exceed the planet's productive capacity by depleting the Earth's natural capital, but this cannot be sustained indefinitely," the study declared.

"It's like drawing down on a bank deposit much faster than it is being fed by interest payments. At some point, the money's going to run out," said one official of the Swiss-based WWF.

The document was issued in advance of next month's World Summit on Sustainable Development in Johannesburg, called just 10 years after the 1992 Rio de Janeiro Earth Summit agreed a plan to avert environmental and social disaster.

Despite some improvements in the use of resources, "we continue to exact an unacceptable price from the Earth's ecosystems...." WWF Director-General Claude Martin said in a foreword.

SPECIES DECLINE

The study found that human economic activity had reduced the number of surviving animal, bird and fish species by 35 percent over the past 30 years.

Freshwater fish had been especially badly hit, losing over half the species in existence in 1970, while key marine species - most of which provide food for the burgeoning population of humans - were down by just under 40 percent.

"The past decade has witnessed fires on an unprecedented scale in the tropical forests of Brazil and Indonesia, coral bleaching that has left vast areas of reef in the Caribbean, Indian and Pacific oceans as ghosts of their former selves," said Martin, a veteran Swiss environmentalist.

The last few years have also seen the ecological devastation of the Black Sea, the Aral Sea in ex-Soviet Central Asia, and Lake Chad in Africa, and loss of wetland and freshwater systems around the world - all from pollution and over-exploitation.

WWF figures showed that while the richer powers drew heavily on Earth's resources, many poor states and their peoples in Africa eked out an existence without drawing on what was available to them within their national borders.

The report said that the Earth had about 11.4 billion hectares of productive land and sea space - 1.9 hectares for each of the planet's six billion people.

But while the average African or Asian consumed natural resources from 1.4 hectares, the average West European used five hectares and the average citizen of the United States and Canada used resources from about 9.6 hectares.

Jonathan Loh, who wrote the report, told Reuters that more efficient use of energy and other resources through better use of technology in recent decades had reduced the overall drawdown but this was being cancelled out by population growth.

The report said that one way governments meeting in Johannesburg could help avoid the looming catastrophe was by promoting education and health care to control population - shorthand for birth control programmes.

Such projects have been championed by United Nations agencies but are strongly resisted by a new coalition of Islamic states, the Vatican, and Christian fundamentalists in the United States who have won the ear of President George Bush.

WWF, formerly the World Wide Fund for Nature and still known in the United States as the World Wildlife Fund, said it was also vital to slash the use of fossil fuels and adopt cleaner sources of energy.