Stars who go green

Matt Damon is just one of the eco-friendly stars going green in Hollywood. The actor is the co-founder of the charity Water.org, which provides clean water and sanitation in communities in Africa, South Asia and Central America.

Brad Pitt

Brad Pitt's Make It Right foundation builds healthy homes, buildings and communities for people in need. The organization, founded by the actor in 2007, began by rebuilding homes in New Orleans after Hurricane Katrina and is also building homes in Newark, N.J., and Kansas City, Mo.

Darryl Hannah

Actress Darryl Hannah has been arrested numerous times while protesting on behalf of environmental causes -- most recently in February 2013 (seen here), while protesting against the proposed Keystone Pipeline at the White House.

Leonardo DiCaprio

A committed environmentalist, Leonardo DiCaprio pledged $1 million to World Wildlife Fund in 2010 for urgent tiger conservation. He also drives a Prius, has solar panels on his home and often flies commercial airlines rather than chartered jets to save fuel. He even narrated, co-wrote and produced the environmental documentary "The 11th Hour," which looks at ways to boost the planet's ecosystems.

Natalie Portman

Natalie Portman, who is an advocate for animal rights, has been a vegetarian since childhood. In 2008, she created a line of vegan-friendly footwear in a partnership with the New York store Te Casan.

Jewel

Singer Jewel founded Project Clean Water in 1997. It is a non-profit charity foundation that is working to improve the quality of life for millions of people by helping to provide clean water on a global scale.

Sienna Miller

Sienna Miller is among the stars who joined Earth Day Network's Billion Acts of Green campaign in 2011. The actress also visited India as an ambassador for Global Cool to help raise awareness among the people of India about the harmful effects of global warming.

Edward Norton

Actor Edward Norton ran the New York City Marathon with a team of Maasai warriors in support of the Maasai Wilderness Conservation Trust in 2009, raising over $1 million through his site, Crowdrise.com.

Ian Somerhalder

Actor Ian Somerhalder created the IS Foundation, which educates and collaborates with people and projects to positively impact the planet. In 2011, the organization collaborated with Conservation International to save over 300 acres of forest.

Maria Menounos

TV personalty Maria Menounos is also among the stars who joined Earth Day Network's Billion Acts of Green campaign in 2011. She's an organic gardener who spoke in 2010 at Earth Day Network's Climate Rally in Washington about the health and cost effectiveness of greener living.

Brandi Carlile

Musician Brandi Carlile established The Looking Out Foundation to financially support causes and organizations that include many environmental groups. She also pledged to continue offsetting the carbon emissions from her tour.

Kelly Preston

Kelly Preston works with The Earth Organization, an an independent, grassroots conservation organization committed to the responsible rehabilitation of the planet. "The environmental issues that face Earth today are no longer the question of our times, they are the issue of our future," she says on the group's website.

Ed Begley Jr.

Long involved in enviromental affairs, actor Ed Begley Jr. is a vegan, lives in a solar-powered home and rides a bike or uses public transportation. He was a member of the Los Angeles Environmental Affairs Commission, but quit in a flap over all the paper the commission was using. In 2007, he and his wife, Rachelle Carson, left, began hosting a green reality TV series called "Living With Ed."

Al Gore

Al Gore's efforts to ignite action to halt global warming, has propelled the former vice president to the top of Hollywood's "green" list. His book, "An Inconvenient Truth," became an Oscar-winning documentary. In 2007, he jointly won the Nobel Peace Prize with a U.N. Panel on Climate Change for their efforts to spread awareness of man-made climate change and to lay the foundations for fighting it.

Laurie David

"An Inconvenient Truth" producer Laurie David, the ex-wife of comedian Larry David, right, is an ardent environmentalist who has written a book on global warming and led a 500,000-person "virtual march" on Washington. Here she joined Sheryl Crow and Florida Gov. Charlie Crist before the Stop Global Warming concert in Gainesville, Fla., on April 16, 2007.

Ted Danson and Mary Steenbergen

Actor Ted Danson has been an environmentalist since childhood. These days, he and his wife, actress Mary Steenbergen, focus their efforts on saving the world's oceans. He was a founder in the 1980s of what is now Oceana and continues to serve on its board and support its activities.

Woody Harrelson

Danson's "Cheers" co-star, actor Woody Harrelson, once climbed the Golden Gate Bridge in San Francisco with members of North Coast Earth First! group. He has denounced animal lab experiments, travelled on a bike tour to draw attention to alternate energy, and has narrated the documentary "Grass."

Robert Redford

Oscar-winning director and acting superstar Robert Redford was an environmentalist long before it became cool in Hollywood. He bought a ski resort in Utah from which he operates the Sundance Institute and its Sundance Film Festival. His Sundance Channel airs a weekly block of environmental programming called "The Green."

Blythe Danner

Actress Blythe Danner, who has been involved in environmental issues such as recycling and conservation for over 30 years, has also appeared in PSAs encouraging use of alternative energy sources and alternative fuel vehicles. In April 2008, she helped unveil new natural gas garbage trucks as part of an initiative to reduce air pollution in the NYC Metro Region.

Pierce Brosnan

An outspoken environmentalist, Irish actor Pierce Brosnan and his wife, Keely Shaye Smith, have spearheaded protests against the development of a natural gas facility off the coast of Malibu, Calif., where they have a home. He spoke on behalf of Greenpeace in the 1990s, has been honored by Danson's Oceana group and was named "Best-dressed Environmentalist" in 2004 by the Sustainable Style Foundation.

Bonnie Raitt

Rock and Roll Hall of Famer Bonnie Raitt was a founding member of Musicians United for Save Energy (MUSE). A committed activist, Raitt has played hundreds of benefit concerts for political and environmental causes.

Julia Louis-Dreyfus

Julia Louis-Dreyfus, the Emmy-winning star of "The New Adventures of Old Christine," has a home in Montecito, Calif., that is solar-powered, radiant-heated and built from recycled materials. An heiress and a longtime activist, she has helped to raise millions for such groups as the Waterkeeper Alliance and the Trust for Public Lands.

Joan Baez

Joan Baez, the 1960s "Queen of Folk Music," has long been active in antiwar, civil rights, social justice and environmental campaigns. On Earth Day 1999, Baez and Bonnie Raitt visited Julia Butterfly Hill, who was camped out at the time atop a giant redwood tree to protect the trees from logging.

Robert F. Kennedy Jr.

He's not an actor and he doesn't live in Hollywood, but his family name has made him a celebrity. This scion of the Kennedy family has linked that name to the environment since he got out of Harvard. A Pace University law professor and master falconer, he has written and lectured widely about the environment and is involved with Riverkeeper, aimed at reducing pollution in the Hudson River and Long Island Sound.

Laura Dern

An outspoken activist, actress Laura Dern, the mother of two, is particularly known for her efforts to raise awareness of environmental toxins that affect children.

Josh Hartnett

Actor Josh Hartnett, star of "The Black Dahlia," and KT Turnstall, both seen here, helped to launch Global Cool, an environmental charity that enlists stars to produce messages telling people how they can help protect the environment.

Alanis Morissette

Alanis Morissette, the Canadian-born singer-songwriter, supports many environmental and political action groups. On her Web site, she has spoken out against Arctic drilling, federal oversight of national parks and the Bush energy plan. She and Keanu Reeves narrated "The Great Warming," a movie about climate change. In 2003, she received the EMA Missions in Music Award for her commitment to environmental causes.