Leonardo DiCaprio is doing his part to save the Earth. The actor hit the stage at the State Department in Washington DC on Tuesday, speaking at the "Our Ocean" conference to address environmental issues. Sporting a suit and tie, Leo talked about the importance of protecting the ocean after a video message from President Obama, which announced the president's plans to create the world's largest ocean preserve. Speaking to an audience of experts, scientists, and government officials, Leo said, "What we need is sustained activism and courageous political leadership. We cannot afford to be bystanders in this preapocalyptic scenario." It's a cause that's close to the actor's heart, as his foundation, The Leonardo DiCaprio Foundation, works toward preserving the Earth. During the conference, Leo pledged $7 million from the foundation to support conservation projects over the next two years. See more photos from Leo's DC appearance below.