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2008 Earth Day on The National Mall

WASHINGTON - APRIL 20: Actor and environmental activist Edward Norton addresses the crowd at the Green Apple Festival concert for Earth Day on the National Mall in Washington, April 20, 2008. (Photo by Paul Morigi/WireImage)

Earth Day: Stars and Their Environmental Causes

We're celebrating Earth Day by taking a look at stars who are taking an active role in protecting our planet with their charitable work.