Wealthy nations should buy tropical forests.

• Position: Carbon Emissions

Wealthy countries collectively willing to spend about $1,000,000,000 annually could prevent the emission of roughly 500,000,000 metric tons of carbon dioxide per year for the next 25 years, suggests research spearheaded by Ohio State University, Columbus. It would take about that much money to put an end to 10% of tropical deforestation--one of the top contributors to greenhouse gas emissions--in the world. This type of program has the potential to reduce global carbon emissions between two percent and 10%.

Under "avoided deforestation," the wealthiest nations would pay landowners in developing countries not to cut down wide swaths of forested land to make way for agricultural uses. Tropical deforestation and the cutting and burning of trees to convert land to grow crops and raise livestock account for about 20% of all human-caused carbon emissions in the world.

The research attaches estimated dollar amounts to each metric ton of carbon that could be saved through avoided deforestation in Africa, Central and South America, and Southeast Asia. The overall cost would be lower than what developed nations would expect to pay to reduce emissions through regulation of industry...