he news from environmental organizations is almost always bleak. The climate is out of whack. Insidious chemicals taint food and drink. Tropical forests are disappearing. Species are perishing en masse. Industrial poisons pollute air, earth and water. Ecosystems are being stressed to the breaking point by the greedy, wasteful consumption of the Western lifestyle and its would-be imitators.

So it is a surprise to meet someone who calls himself an environmentalist but who asserts that things are getting better, that the rate of human population growth is past its peak, that agriculture is sustainable and pollution is ebbing, that forests are not disappearing, that there is no wholesale destruction of plant and animal species and that even global warming is not as serious as commonly portrayed.

Strange to say, the author of this happy thesis is not a steely-eyed economist at a conservative Washington think tank but a vegetarian, backpack-toting academic who was a member of Greenpeace for four years. He is Dr. Bjorn Lomborg, a 36-year- old political scientist and professor of statistics at the University of Aarhus in Denmark. Dr. Lomborg arrived at this position, much to his own astonishment, through a journey that began in a Los Angeles bookshop in February 1997.

Dr. Lomborg was leafing through an issue of Wired magazine and started reading an interview with Dr. Julian L. Simon, a University of Maryland economist who argued in several books that population was unlikely to outrun natural resources.

But Dr. Simon, who died in 1998, is more widely known for his solution to the airline overbooking problem (having airlines pay passengers to take a later flight) and for a 1980 bet with Dr. Paul Ehrlich, president of Stanford University's Center for Conservation Biology. Dr. Lomborg bet that any five metals chosen by Dr. Ehrlich would be cheaper in 1990; Dr. Ehrlich lost on all five.

Dr. Lomborg felt sure that Dr. Simon's arguments were "simple American right-wing propaganda," though presented with enough seriousness that they would be worth rebutting. Back in Aarhus, he started nightly study sessions with his statistics students to debunk Dr. Simon's contentions, using figures drawn from reports of the World Bank, the Food and Agriculture Organization, the United States Environmental Protection Agency, the International Panel on Climate Change and other gatherers of official facts.

"Three months into the project, we were convinced that we were being debunked instead," Dr. Lomborg said. "Not everything he said is right. He has a definite right-wing slant. But most of the important things were actually correct."

Dr. Lomborg has presented his findings in "The Skeptical Environmentalist," a book to be published in September by Cambridge University Press. The primary targets of the book, a substantial work of analysis with almost 3,000 footnotes, are statements made by environmental organizations like the Worldwatch Institute, the World Wildlife Fund and Greenpeace. He refers to the persistently gloomy fare from these groups as the Litany, a collection of statements that he argues are exaggerations or outright myths.

Dr. Lomborg also chides journalists, saying they uncritically spread the Litany, and he accuses the public of an unfounded readiness to believe the worst.

"The Litany has pervaded the debate so deeply and so long," Dr. Lomborg writes, "that blatantly false claims can be made again and again, without any references, and yet still be believed." This is the fault not of academic environmental research, which is balanced and competent, he says, but rather of "the communication of environmental knowledge, which taps deeply into our doomsday beliefs."

To understand the world as it is, Dr. Lomborg says, it is necessary to look at long-term global trends that tell more of the whole story than short-term trends and are less easy to manipulate.

For example, the Worldwatch Institute, in its 1998 "State of the World" report, said, "The world's forest estate has declined significantly in both area and quality in recent decades." But the longest data series of annual figures available from the United Nations' Food and Agriculture Organization shows that global forest cover has in fact increased, to 30.89 percent in 1994 from 30.04 percent of global land cover in 1950. The Worldwatch report goes on to claim that because of soaring demand for paper, "Canada is losing some 200,000 hectares of forest a year." The cited reference, however, says that "in fact Canada grew 174,600 more hectares of forest each year," Dr. Lomborg writes.

Janet Abramovitz, Worldwatch's forest expert, said the world forest cover had shrunk significantly in the last 20 years. She based that contention on a different, shorter series of Food and Agriculture Organization statistics but declined to cite a percentage. The institute's figure on Canadian forest loss was an error, she said.

In its report for 2000, the Worldwatch Institute cited the dangers it had foreseen in 1984 — "record rates of population growth, soaring oil prices, debilitating levels of international debt and extensive damage to forests from the new phenomenon of acid rain" — and lamented that "we are about to enter a new century having solved few of these problems."

But in his book, Dr. Lomborg cites figures from the United States Census Bureau, the International Monetary Fund, the World Bank and the European Environment Agency to show that the rate of world population growth has actually been dropping sharply since 1964; the level of international debt decreased slightly from 1984 to 1999; the price of oil, adjusted for inflation, is half what it was in the early 1980's; and the sulfur emissions that generate acid rain (which has turned out to do little if any damage to forests, though some to lakes) have been cut substantially since 1984.

In an interview, the president of the Worldwatch Institute, Christopher Flavin, agreed that progress had been made in the four problems cited in the institute's 1984 report, but he said that had been mentioned in other institute reports. "If you read through our materials as a whole," Mr. Flavin said, "many of these improvements are acknowledged."

Dr. Lomborg has also been unable to find strong support in the official statistics for the regular predictions of disaster from Dr. Ehrlich. "In the course of the 1970's," Dr. Ehrlich wrote in "The Population Bomb," published in 1968, "the world will experience starvation of tragic proportions — hundreds of millions of people will starve to death."

Although world population has doubled since 1961, Dr. Lomborg writes, calorie intake has increased by 24 percent as a whole and by 38 percent in developing countries.

Dr. Lomborg also takes issue with some global warming predictions. In assessing how waste gases could warm the world's climate, he says, there are four wild cards that affect the climate change models.

One is the multiplier effect of carbon dioxide — as it heats the atmosphere a little, the air can hold more water, and that heats the atmosphere a lot more. How much more is in question, but Dr. Lomborg cites satellite and weather balloon data that seem to weaken the case for a strong multiplier effect.

The other three wild cards, Dr. Lomborg says, are the role of clouds, the effect of aerosols and the effect of the sunspot cycle on earth's climate.

Dr. Lomborg believes that when it comes to computer models of climate change, the International Panel on Climate Change deals all four wild cards in a way that exaggerates the effect of greenhouse gases. This means, in his view, that the actual warming will be at the cooler end of the panel's predicted range.

He contends that the internationally agreed Kyoto targets for reducing carbon dioxide emissions will impose vast costs for little result. A more effective approach, according to Dr. Lomborg, would be to increase research on alternative sources of energy, like solar and fusion.

But Dr. Kevin Trenberth of the National Center for Atmospheric Research said that new satellite data were likely to point toward a strong multiplier effect for carbon dioxide.

And while Dr. Michael Oppenheimer, an expert on global warming at Environmental Defense, agrees that clouds and aerosols are still weak points in the climate models, he says Dr. Lomborg's contention on the effects of the sunspot cycle is not widely accepted. As to Dr. Lomborg's policy recommendations, Dr. Oppenheimer said that investing in technology alone was "like betting the farm on a policy in which we have less confidence than emissions reduction." In his view, a broad- based technology push would turn into a pork-barrel program and be far less efficient than the technology that would develop in response to a requirement to reduce emissions.

"The Skeptical Environmentalist" portrays several other elements of the Litany as little more than urban myths. One is the prediction that the world's forests and a large number of species are headed for catastrophe.

Dr. Lomborg believes that forest loss has been less serious than is often described — only 20 percent since the dawn of agriculture, not 67 percent, as stated by the World Wildlife Fund. He also puts the present annual rate of loss at 0.46 percent, as calculated by the Food and Agriculture Organization, rather than at 2 percent or more, the figure cited by many environmentalists.

Given that the forests are not doing that badly, he is skeptical of claims that the world is about to lose half or more of its species. The often quoted figure that 40,000 species are lost every year comes from a 1979 article by Dr. Norman Myers, an ecologist at Oxford University. But this figure, Dr. Lomborg says, was not based on any evidence, just on Dr. Myers's conjecture that one million species might be lost from 1975 to 2000, which works out to be 40,000 species a year.

The International Union for the Conservation of Nature, which maintains the Red Book of endangered species, concluded in 1992 that the extinction figures for mammals and birds were "very small" and that the total extinction rate, assuming 30 million species, was probably 2,300 species a year.

Nonetheless, Dr. Lomborg says, Dr. Myers repeated his estimate in 1999 with a warning that "we are into the opening stages of a human- caused biotic holocaust."

Dr. Myers confirmed in an interview that the figure of 40,000 extinctions a year had come from his estimate. He said that it was an illustration used to make his argument clear and that he gave figures only "when I am speaking to a political leader or policy maker who says that in order to sell his message, he absolutely must have some number."

The International Union for the Conservation of Nature's estimate was too low, Dr. Myers said, because it considered a species extinct only after none of its members had been sighted for 50 years. "All I am trying to do is to demonstrate that we are in the opening phase of a mass extinction," he said.

Though no longer a member of Greenpeace, Dr. Lomborg still counts himself as an environmentalist and portrays his critique as based on the outlook of a leftist. "I'm a left- wing guy," he says, "and a vegetarian because I don't want to kill animals — you can't play the `he's right- wing so he's wrong' argument."

He believes that the environment must be protected and that regulation is often necessary. But exaggerating problems distorts society's priorities, he says, and makes it hard for society to make the best decisions.

Writing about environmentalists, he says, "The worse they can portray the environment, the easier it is for them to convince us that we need to spend more money on the environment rather than on hospitals, child day care, etc."

Those who abandon long-held faiths are often strident advocates of their new views. But Dr. Lomborg displays little of the convert's zeal. His aim is not to preach free-market solutions for every problem or to deny that threats to the environment exist.

His motive, he says, is simply to document that the facts, in his view, tell a far brighter story than the Litany. Thomas Malthus argued in 1798 that population growth was certain to outrun food supply. As Dr. Lomborg sees it, Malthus's gloomy predictions still hold an iron grip over many minds, and are still wrong.