By THE ASSOCIATED PRESS

UNITED NATIONS, Aug. 13 (AP) — The more than 100 world leaders who will attend the Earth Summit this month must tackle the double threat of widespread poverty and increasing environmental devastation that has left billions of people facing food and water shortages, according to a United Nations report released today.

The report reviews data from the United Nations and international organizations about the use of natural resources and presents a sobering assessment of the planet.

Forests are being destroyed, drought is becoming more intense, sea levels are rising, agricultural production cannot keep up with the demand for food, many plant and animal species are at risk of extinction, and air and water pollution are killing millions of people, the report asserts.

"The real threat that we face now is the insidious global spread of poverty and environmental stress — and that is the real security threat that we need to address," said Nitin Desai, who heads the United Nations department that created the report, the Department for Economic and Social Affairs. Mr. Desai who will serve as chairman of the Earth Summit, which will meet in Johannesburg from Aug. 26 to Sept. 4.

At a news conference to announce the report's release, Mr. Desai said that there had been excellent small-scale initiatives to tackle many of the problems and that the great challenge of Johannesburg would be to mobilize governments, voluntary organizations and the private sector to implement those initiatives on a large scale.

Another challenge, he said, is to connect the agenda to preserve the world's natural resources with the goals adopted by more than 150 world leaders at the United Nations Millennium Summit in 2000. Those goals include reducing by half the number of people living in poverty and giving every child an elementary school education by 2015.

"You can't reduce poverty unless you also address land and water," Mr. Desai said. "You can't improve children's health without addressing sanitation and air quality."

The report also said that the world was failing to produce enough food for a global population of 6 billion, with almost 800 million chronically undernourished. That number is declining. But the world's population is projected to reach 8 billion by 2025.