Leonardo DiCaprio's most important role is no act.
To be honest, I haven't always liked DiCaprio's movies (though he's starting to grow on me as an actor), but I appreciate his work on environmental issues. Many celebrities sign their names to nonprofit efforts, but endorsement of and actual work on social issues are two different things.
DiCaprio backs up his words with involvement. In 2007, he produced The 11th Hour, a documentary on global warming. He's also met with world leaders to find ways of protecting tigers. Most recently, his foundation made a $3 million donation to Oceana's efforts to protect marine habitat in both the Arctic Ocean and the Pacific Ocean. For more information on his foundation, click here.
Yesterday, I saw a news article talking about why DiCaprio hasn't won an Academy Award. Although I'm sure he'd love to win one, he seems to realize he's playing in a much larger theater, and I think he would be willing to trade an Oscar for the chance to make an impact on environmental issues.
Sequels rarely appeal to me, but I can't wait for the next installment of DiCaprio's environmental work.