The world's cleanest countries

The declining health of Mother Earth has drawn growing attention over the last two decades, with countries coming together to fight a range of environmental threats, from declining fishing stocks to global warming.

Witness the Kyoto Protocol, the first widely adopted set of environmental protection guidelines, which emerged during the 1990s and took effect in 2005. Kyoto led to the development of the first large-scale emissions trading market, Europe's Greenhouse Gas Emission Trading Scheme, which puts caps on carbon dioxide pollution. A similar carbon market, the Regional Greenhouse Gas Initiative, began operating at the start of this year in 10 Eastern US states.

In spite of nearly universal support for a cleaner globe (the US was one of only a few countries that failed to adopt Kyoto), it's mainly the rich nations that enjoy pristine environments, according to the Environmental Performance Index. Columbia University's Center for International Earth Science Information Network and Yale University's Center for Environmental Law and Policy developed the index to highlight the cleanest countries, and give laggards the opportunity to benchmark efforts to improve their own environments and the health of their citizens.

Switzerland tops the list with an overall EPI score of 95.5 out of 100, while European countries account for 14 of the top 20 environmental performers. Europe has the infrastructure to provide clean drinking water and treat waste water, lowering the likelihood that Europeans will suffer from waterborne disease. Europe scores consistently well in EPI's environmental health ranking, which measures the effects of pollution on human health.

A second broad measure, ecosystem vitality, measures the health of fisheries, the amount of greenhouse gases a country pumps into the air and how well it preserves the diversity of its plants and animals. On this measure, the performance of developed countries diverges. Scandinavia, with its low population and vast open spaces, enjoys pristine forests and relatively little air pollution.

The US, once a leader in environmental protection, has failed to keep pace. "Starting 25 years ago, the United States started to fall behind in relative terms. Before that time, Europe always had dirtier air and drinking water," says Mark Levy, associate director of Columbia University's earth science center.

Then-President George H W Bush signed the last significant American air quality legislation in 1990, an amendment to the Clean Air Act. The US scores a meager 63.5 on the ecosystem vitality scale, vs. an average score of 74.2 for the world's richest nations. The US' overall EPI score is 81, putting it in 39th place on the list.

Improved science has led to a better understanding of the linkage between pollution and human health. "The science that's come out has shown that the harder you look for air-pollution-related health problems, the more you find," says Levy. "Scientists have recommended that environmental regulations be tightened. Europe has done that, but the US has been stuck."

Countries are also handicapped according to their locations, with sub-Saharan African countries suffering from scant and poor-quality water, and Asian countries affected by depleted fishing stocks. Switzerland's weakest marks come in agriculture, in part because farmers in the mountainous country have a tendency to overwork their limited crop land.

A few developing nations break into the top 10 of the rankings. Costa Rica has a per-capita gross domestic product of $11,600, but ranks fifth overall as it protects its forests and rich biodiversity, both lures for ecotourists.

Another Latin American country, Colombia, ranks ninth overall. The country carefully guards its coffee plantations, a source of lucrative exports. Ironically, the presence of guerrillas and drug lords also makes the countryside hard to develop, even as developers rapidly cut down rainforest in neighboring Brazil.

EPI researchers caution that the information used to develop the scale often comes from local sources and can be of less-than-ideal quality, especially in developing countries. They ranked 149 countries, and left the remaining 50 or so off the list for insufficient data.