10 Men Who Changed the Environmental Movement Forever

Shaped by unwitting leaders like Henry David Thoreau in the middle of nineteenth century Massachusetts, and organized by tech-savvy global environmental activists like Bill McKibben at the start of the twenty-first, the environmental movement has grown to become an incredibly strong, if not always cohesive, political movement.

In light of the 40th anniversary of Earth Day on April 22, we want to recognize some of the leaders and thinkers who have had a profound impact on environmentalism as we know it. To begin with, we present you with 10 fellows who have played critical roles in shaping the modern environmental movement. See also our '10 Women Who Changed the Environmental Movement Forever.'

(Compiled by Becky Striepe with editing by Timothy Hurst)