The report, released Tuesday, reviewed the most authoritative data from U.N. and international organizations about the use of natural resources.
Fossil fuel consumption and carbon emissions continued to rise in the 1990s, particularly in Asia and North America, according to the study. Signs of climate change linked to global warming were more apparent, including more frequent and intense droughts in parts of Asia and Africa and rising sea levels.
During the 1990s, the report said, 2.4 percent of the world's forests were destroyed, almost all in tropical regions in Africa and Latin America. The estimated total area destroyed - 220 million acres - is larger than the size of Venezuela.
U.N. Undersecretary-General Nitin Desai, who will lead the Earth Summit in Johannesburg from Aug. 26 to Sept. 4, said the report underscores that the world is at a crucial crossroads in the new millennium.
"If we do nothing to change our current indiscriminate patterns of development, we will compromise the long-term security of the Earth and its people," he said.
More than 100 world leaders are expected to attend the summit and adopt a plan aimed at accelerating economic development while preserving the environment.
The report by the U.N. Department for Economic and Social Affairs, which Desai heads, focuses on five key issues: water and sanitation, energy, agricultural productivity, biodiversity and human health.
The need to feed a rising global population - now over 6 billion and projected to reach 8 billion by 2025 - is exacerbated by an increase in food consumption, from 2100 calories to 2700 calories a day in developing countries, and from 3000 calories to 3400 calories a day in industrialized nations, the report said.
At the same time, it said, the capacity to produce enough food is diminishing, especially in developing countries.
The report found that global water use has increased six-fold over the last century, at twice the rate of population growth, and that agriculture represents 70 percent of this consumption. The greatest drain on the world's freshwater supplies is inefficient agricultural irrigation systems.
Meanwhile, about 40 percent of the world population face water shortages; by 2025 that figure is expected to increase to 50 percent, the report said.
"A top priority at the summit is the need to agree on policies and programs that improve agricultural yields in order to meet our long-term food needs," Desai said. "Equally pressing is the goal of expanding sustainable agricultural practices, including the introduction of efficient irrigation systems."
Despite some recent improvements, 1 billion people still lack access to safe drinking water and 2.5 billion lack adequate sanitation facilities, the report said.
More than 3 million people die every year from the effects of air pollution and 2.2 million people die from contaminated water, it found.
The great majority of those who die from polluted air are children in developing countries who suffer from respiratory infections, the report said.
The report praises some small-scale programs that address problems such as urban air pollution and child mortality linked to unsafe water. But it said these gains will be lost if action is not taken soon on a much larger scale.
By Edith M. Lederer