Divergence

Correction Appended

WASHINGTON, Jan. 23 - Countries from Northern and Central Europe and South America dominated the top spots in the 2005 index of environmental sustainability, which ranks nations on their success at such tasks as maintaining or improving air and water quality, maximizing biodiversity and cooperating with other countries on environmental problems.

Finland, Norway and Uruguay held the top three spots in the ranking, prepared by researchers at Yale and Columbia Universities. The United States ranked 45th of the 146 countries studied, behind such countries as Japan, Botswana and the tiny Himalayan kingdom of Bhutan, and most of Western Europe.

The lowest-ranking country was North Korea. Among those near the bottom were Haiti, Taiwan, Iraq and Kuwait.

The index is the second produced in collaboration with the World Economic Forum, which meets in Davos, Switzerland, this week. The first complete index, in 2002, produced outrage and soul-searching in lower-ranking countries like Belgium and South Korea, said Daniel C. Esty, the director of the Yale Center for Environmental Law and Policy and an author of the report.

The report is based on 75 measures, including the rate at which children die from respiratory diseases, fertility rates, water quality, overfishing, emission of heat-trapping gases and the export of sodium dioxide, a crucial component of acid rain.

In its opening chapter, the Environmental Sustainability Index report said: "Although imperfect, the E.S.I. helps to fill a long-existing gap in environmental performance evaluation. It offers a small step toward a more vigorous and quantitative approach to environmental decision making."

The report also cited a statistically significant correlation between high-ranking countries and countries with open political systems and effective governments.

The report's flaws stem largely from inadequate data, Mr. Esty said, adding that the ranking system is at best approximate, because some individual scores had to be imputed in many cases. But he said that data might improve in coming years.

He also said a system that rated Russia, whose populated western regions have undergone extraordinary environmental degradation, as having greater environmental sustainability than the United States had inherent weaknesses.

At 33, Russia's ranking, Mr. Esty said, is in large part a consequence of the country's vast size. While it "has terrible pollution problems" in the western industrial heartland, he said, its millions of unsettled or sparsely settled acres of Asian taiga mean "it has vast, untrammeled resources and more clean water than anywhere in the world." So, he added, "on average, Russia ends up looking better than it does to someone who lives in western Russia."

Because such differences make many countries inherently difficult to compare, he said, this report also analyzed seven clusters of similar countries; in this analysis, the United States ranked slightly below the halfway point among 24 members of the Organization of American States.

Another cluster ranked countries whose land is more than 50 percent desert, including Israel and much of the Arab world. In this group, Israel ranked second, after Namibia, and the best-performing Arab countries were Oman and Jordan. But some nations with considerable oil wealth, like Iran, Saudi Arabia and Kuwait, ranked in the bottom third.

After Finland, Norway and Uruguay, the top 10 countries in the overall rankings were, in order, Sweden, Iceland, Canada, Switzerland, Guyana, Argentina and Austria.

Irritation at low rankings in the 2002 index spurred countries like Mexico and South Korea to improve their efforts, Mr. Esty added. Young Keun Chung, an environmental economist with South Korea's state Korea Environment Institute, agreed, saying: "The first time we were shocked. Our government wanted to improve our situation. So we concentrated on improving environmental policy, pollution problems, traffic problems and everything."

South Korea moved up 13 spots between 2002 and the new report, but was only No. 122 in the overall index, and 14th out of 21 high-density countries in which more than half the land has a population density greater than 100 people per square kilometer.

Correction: January 28, 2005, Friday:

An article on Monday about a study that ranks nations by their success in managing environmental problems referred incorrectly to an air pollutant that is an important component of acid rain. It is sulfur dioxide, not sodium dioxide.