Healthy ecosystems provide us with fertile soil, clean water, timber, and food. They reduce the spread of diseases. They protect against flooding. Worldwide, they regulate atmospheric concentrations of oxygen and carbon dioxide. They moderate climate. Without these and other “ecosystem services,” we’d all perish.

Biofuels are held up as a relatively easy solution to the twin problems of petroleum dependence and carbon emissions. But new research suggests that fuels such as corn-based ethanol may cause as many problems as they solve.