Robert Redford is one of those Hollywood icons who was never content to be a celebrity. He wanted to put his fame and fortune to good use, and he's done that through tireless advocacy on behalf of the environment. A trustee of the Natural Resources Defense Council since 1974, Redford was an early proponent of renewable energy and has been a fierce protector of Western wildlands. In an OnEarth interview, Redford reflects on a lifetime of environmental activism, his love for the West, and why — on its 40th anniversary — Earth Day should be more important than ever. Hear excerpts above or read the whole interview.