The Sierra Gorda Biosphere Reserve is a protected area in Central Mexico. It's about the size of Rhode Island, with a population of roughly 100,000 people. Every year, thousands of Mexicans leave for the United States to find work; most go illegally. But leaders in the Sierra Gorda are hoping that environmentalism will turn this area around.

The World's Jason Margolis went to the Sierra Gorda to report on efforts to raise funds from the industrialized world to plant new trees and protect existing forests. Trees remove the greenhouse gas carbon dioxide from the atmosphere, which contributes to global warming.