IMAGES: The world's SEXIEST celebrity environmentalists!

Rodale.com has compiled a list of 50 famous personalities who have contributed greatly to green causes -- we bring you the top 20!

Website Rodale.com drew up a list of 50 celebrities who deserve recognition for their aid and support of ecological causes, in order of importance.

All the beautiful people in the following pages have taken it upon themselves to preserve and protect the environment -- and maybe you should take a cue from them and follow suit!

1. Gretchen Bleiler

This 31-year-old American Olympic snowboarder topped the Rodale list for her efforts in helping to combat global warming by standing up for the regulation of greenhouse gas emissions.

Gretchen is a member of Protect Our Winters, a worldwide mission that engages leading international snow sports enthusiasts to lead against climate change. She also visits educational institutions across America to encourage recycling of plastic among youngsters and owns a business that manufactures non-toxic, stainless steel water bottles.

Hollywood yummy mummy Jessica has launched The Honest Company, a business that offers safe, organic products for infants like plant-based diapers and organic baby oils.

A patron of several charitable organisations like Safer Chemicals and Habitat for Humanity, she's also working on a book to promote a healthy, environment-conscious lifestyle that is expected to release next year.

Debuting in the list at Number Three is actor Damon. In 2009, he established Water.org, a non-profit organisation that aids a number of developing countries with safe water and sanitation (incidentally, India is on their list).

He's also actively participated in using his celebrity to spread awareness -- he narrated a documentary about climate change last year and his upcoming movie Promised Land is about a town consumed by natural gas drilling and its dangers. Damon wrote the movie and is also starring in it.

Few celebs are as passionate about animals as Alicia. The new mother is a hardcore vegan and staunch supporter of People for the Ethical Treatment of Animals (PETA).

Alicia is constantly promoting a vegan lifestyle -- her book The Kind Diet made it to the New York Times' bestseller list and she's also designed a range of vegan products for EcoTools, which retail across the US.

Here's another PETA pledger. Academy Award-nominated Gosling wrote a letter on their behalf last year, addressed to the U.S. Department of Agriculture (USDA), urging them to revoke a method of killing poultry birds that involved suffocating them, in favour of a more humane approach.

He has also previously written letters to fast food giants KFC and McDonald's, calling them out for their cruelty to animals and to convince them of heeding PETA's animal welfare reforms.

This may come as a surprise, but the kind-hearted Duchess of Cambridge made it to sixth place because of the many measures taken to ensure her monster of a wedding took the environment into consideration at all stages.

For one, she and Prince William did not register for gifts, but requested all guests to donate to charities, several conservation and environmental organisations among them. And instead of exotic blooms, Rodale.com reports that they chose in-season flowers as part of their decor, sourced from a local eco-florist. The website further states that the fact that her engagement ring is a family heirloom, and not a new bauble or blood diamond, also testifies to the royal couple's eco-mindedness.

The American footballer and NFL star may look tough, but he seems to have a soft heart. One of Witherspoon's vacation homes is an Animal Welfare-approved farm, where cattle, chicken and sheep are all raised using organic, natural foods.

And their presence on the land has a great positive effect, naturally allowing soil carbon sequestration -- the process of transferring carbon dioxide from the atmosphere into the soil. While it is toxic to humans, carbon dioxide is a greenhouse gas valuable to the environment.

The Maroon 5 frontman, along with his band, has founded the Green Music Group -- in their own words, "a large-scale, high-profile environmental coalition of musicians, industry leaders and music fans using our collective power to bring about widespread environmental change within the music industry and around the globe."

Levine is also a spokesman for not one but several eco-organisations, forever encouraging people through public service messages to embrace a greener way of life.

Alexandra hails from an internationally-renowned family of conservationists -- her grandfather was the famous French ecologist and explorer Jacques Cousteau and she is carrying his legacy forward proudly.

Alexandra is the founder and president of Blue Legacy, a nonprofit organisation that advocates solving critical water issues. They also advocate non-toxic living at home, which in turn reflects positively on our water bodies -- and it benefits us too.

You may enjoy Johnson's music, but do you know that he records in a solar-powered studio and his album covers are printed on 100 percent recycled paper?

When on tour, his crew uses a biodiesel bus to get around and at every stop, a catering team sees to sourcing organic, sustainable food.

Johnson has also established a charity, the Jackson Ohana Charity Foundation, which funds various green projects and donated 100 percent of the proceedings from his 2008 and 2010 tour toward such ends.

The diminutive actress is an avid sealife activist.

Spokeswoman of The Whaleman Foundation, an organisation that aims to protect whales from hunting, pollution and climate changes, Rodale.com reports that Hayden has even appeared in The Cove, an Academy Award–winning documentary that reveals the cruelty of Japanese dolphin hunting.

In her free time, she pursues free-diving in a bid to learn more about the ocean's inhabitants and how best to protect them.

His surname may ring a bell -- Philippe is the grandson of great explorer and environmental activist Jacques Cousteau.

Along with his mother and sister, he has established EarthEcho International, an organisation that encourages youngsters to protect the oceans and all they contain. Other ventures include Azure Worldwide, an environmental consulting, development, marketing and media company and serving as Chief Ocean Correspondent for TV channels Animal Planet and Planet Green, shooting several underwater programmes that educate the public about sea creatures.

Philippe also works with hotels and resorts around the world to help them go green with eco-friendly operations.

David was born into a dynasty of wealthy bankers and financiers, but has taken it upon himself to shoot out in a different direction -- the young British millionaire is a passionate adventurer and environmentalist.

Head of Adventure Ecology, an expedition group raising awareness about climate change, he has participated in several challenging eco-missions across the world and has received several accolades for his efforts, among them the title of 'Emerging Explorer' from National Geographic, being appointed an international ambassador by NGO Clean Up The World and a nomination as Young Global Leader by the World Economic Forum.

David's most recent notable feat was an expedition across the Pacific Ocean from San Francisco to Sydney, covering 8,000 nautical miles in a 60-foot catamaran called the Plastiki -- because it was a vessel created entirely from plastic bottles, created to raise awareness about marine pollution.

There's more to this Academy Award-winning actress than her looks.

Harvard-educated Natalie has been a vegetarian since childhood and came out with a line of vegan footwear in 2007, donating the profits to animal charities and eco-conservation efforts.

The same year, she also travelled to Rwanda with American zookeeper Jack Hanna to film a documentary, Gorillas on the Brink, in which she is seen interacting with the animals and seeks to highlight their plight.

In addition to vegetarianism, Natalie also refuses to use any animal products and never wears fur, feathers or leather.

Summer is often referred to as the World's First Eco-Model, because she seeks to align fashion with environmental causes.

She works with eco-conscious companies and designers and is a tireless spokeswoman for a greener way of life; she has hosted television specials to promote an environment-friendly lifestyle and launched sustainable, eco-friendly products.

Summer is also involved with Energy Action Coalition (an organisation that campaigns to rally youth to the clean energy movement) and several efforts to reduce deforestation across the world.

For her efforts, she has been honoured by Vanity Fair Magazine as 'A Global Citizen', Outside Magazine as a 'Green All-Star' and environment advocacy group Earth First!'s 'Hottest Girl in Green'.

The Aussie-born actress and wife of Ellen DeGeneres is an animal lover and vegan. Together, the couple are strong supporters of Gentle Barn, a California-based sanctuary for abused animals and Farm Sanctuary, a nonprofit that rescues animals from cruel factory farms.

Portia also supports Alley Cat Allies, an organisation dedicated to protecting and improving the lives of cats.

A hunk with a heart, Jake has long supported the fight against climate change and even flew to the Arctic to promote awareness for the cause after filming the movie The Day After Tomorrow.

Jake's also gone on record to state that he spends $400 a year to have trees planted in a Mozambique forest, partly to promote the Future Forests program. And he certainly does his bit at home too, recycling regularly.

Coming in at eighteen on Rodale's list we have the inimitable Mr Pitt, whose unceasing efforts to rebuild a neighbourhood in New Orleans after Hurricane Katrina have a green tinge to them, like energy-efficiency measures, solar-panel-topped roofs and community gardens.

His Make It Right foundation financed and constructed 150 sustainable, affordable new houses in the devastated area and today it is one of the greenest neighbourhoods in the US.

For his efforts, Pitt received an award in recognition of the project from the US Green Building Council and even met President Barack Obama to promote green housing as a national model and discuss funding.

When she played environmental activist Erin Brockovich on screen she received critical acclaim, but Julia also tries to keep things green in real life. Following the movie, she became a spokesperson for Earth Biofuels, a company that develops renewable energies.

The actress is also a strong supporter of organic diets and gardening and grows one of her own in her Malibu home.

And finally, we come to the popstar-turned-actor who owns Mirimichi, the world's greenest golf course -- it's the only one of its kind to be certified for both its bird-friendly habitat preservation and low pesticide use, as well as the resource management of its greens.

Justin is also one of many celebs who try to reduce their carbon footprints and takes special measures to do the same while on tour.

In October last year, he was awarded The Environmental Media Awards' 'Futures' prize, which recognises green celebrities from across the entertainment field.