The United States lags behind 50 nations in environmental health, according to the recently released Environmental Sustainability Index, an annual study led by Yale’s Daniel Esty, director of the Yale Center for Environmental Law and Policy.

Conducted by Yale, Columbia University, and the World Economic Forum and released earlier this month at the WEF’s annual meeting, the 3-year-old ESI measures environmental conditions across142 nations.

The ESI report indicates each nation’s performance in many specific categories, and ranks nations with an overall index. The executive summary of the ESI identifies five broad categories for the measurements used in the calculations — environmental systems, reducing stresses, reducing human vulnerability, social and institutional capacity, and global stewardship.

Finland, Norway, Sweden, Canada and Switzerland took the lead in the ESI ranking, while Haiti, Iraq, North Korea, Kuwait and the United Arab Emirates fell to the bottom of the pack. The study indicated a strong correlation between economic development and environmental sustainability, but at the same time suggested that economic conditions are not the sole determinant of environmental health. Many nations of comparable GDP per capita showed wide variation in ESI ranking.

Esty attributed the United States’ 51st-place standing to an uneven performance. In terms of water quality and air pollution, he said, the United States is a global leader, yet its control of greenhouse gas emission ranks among the world’s lowest. He explained that the United States effectively manages local problems while largely ignoring those of a wider scope.

Esty said he feels the small nations at the top of the rankings have a “greater appreciation for reciprocity,” and thus place more emphasis on decisions with implications outside their borders. He also suspects that the political system of the United States — in which representatives are judged on short-term accomplishments, and special interests often dominate policy — has not been conducive to long-term environmental thinking.

The ESI represents an “attempt to revolutionize environmental decision making,” Esty said. Because little hard data has been collected on environmental performance, he said, environmental debates are often dominated by “rhetoric and emotion.”

In light of recent advances in data collection, storage and analysis, Esty said it is time to move the environment into the realm of empirical analysis alongside disciplines such as business. He said that the concrete measurements the ESI presents have powerful potential for comparing environmental tactics, financial strategizing and promoting competition between nations.

While the study has generated much international attention — policy-makers have called upon the ESI’s creators for advice on environmental strategy — Noah Chesnin ’04, a chairman of the Yale Student Environmental Coalition, said the study also has implications on a local level.

“However negative the numbers may be, professor Esty’s numbers only continue to fuel YSEC’s drive to make Yale, New Haven and the U.S. more environmentally responsible,” Chesnin said. “Now we have firm comparative numbers to advance our case.”