Great post by the New York Times John Tierney titled Use Energy, Get Rich and Save the Planet:

When the first Earth Day took place in 1970, American environmentalists had good reason to feel guilty. The nation’s affluence and advanced technology seemed so obviously bad for the planet that they were featured in a famous equation developed by the ecologist Paul Ehrlich and the physicist John P. Holdren, who is now President Obama’s science adviser.

Their equation was I=PAT, which means that environmental impact is equal to population multiplied by affluence multiplied by technology. Protecting the planet seemed to require fewer people, less wealth and simpler technology — the same sort of social transformation and energy revolution that will be advocated at many Earth Day rallies on Wednesday.

But among researchers who analyze environmental data, a lot has changed since the 1970s. … The old wealth-is-bad IPAT theory may have made intuitive sense, but it didn’t jibe with the data that has been analyzed since that first Earth Day. By the 1990s, researchers realized that graphs of environmental impact didn’t produce a simple upward-sloping line as countries got richer. The line more often rose, flattened out and then reversed so that it sloped downward, forming the shape of a dome or an inverted U — what’s called a Kuznets curve.

In dozens of studies, researchers identified Kuznets curves for a variety of environmental problems. There are exceptions to the trend, especially in countries with inept governments and poor systems of property rights, but in general, richer is eventually greener. As incomes go up, people often focus first on cleaning up their drinking water, and then later on air pollutants like sulfur dioxide.

Of course, even if rich countries’ greenhouse impact declines, there will still be an increase in carbon emissions from China, India and other countries ascending the Kuznets curve. While that prospect has environmentalists lobbying for global restrictions on greenhouse gases, some economists fear that a global treaty could ultimately hurt the atmosphere by slowing economic growth, thereby lengthening the time it takes for poor countries to reach the turning point on the curve.