'Green' Stars Talk the Talk ... but Do They Walk the Walk?

Hollywood's gone green — or so everybody says. Whether they're driving hybrid cars, shunning bottled water or making do with just one square of toilet paper, A-listers from Natalie Portman to Brad Pitt are joining the eco-chic bandwagon.

But who's really green, and who's just an imposter?

Laurie David, producer of Al Gore's Oscar-winning global warming documentary "An Inconvenient Truth" and estranged wife of actor/writer Larry David, has become one of the most widely known environmental activists. But Jackie Mendez-Diez, David's neighbor in celeb-popular Martha's Vineyard, Mass., told FOXNews.com she's a hypocrite.

Video: 'Green' Stars Don't Always Practice What They Preach

Photo Essay: Green Stars

"I normally wouldn't care, it would just be between neighbors, but this woman was going around the country telling everyone to reduce their carbon footprint, and I really objected," Mendez-Diez said.

"She built this reputation on confronting people about their lifestyle — about what kind of car they drive, about everything they do — and in her personal life she took 75 acres of undeveloped wetlands and developed swimming pools during a six-year construction project. It's ridiculous!"

A representative for David declined to comment.

Indeed, John Buckley, managing director of Carbon Footprint, an eco-awareness non-profit group based in the U.K., says there are many stars who don't practice what they preach when it comes to saving the Earth.

"At the moment it's kind of fashionable for pop stars or celebrities to look green," he told FOXNews.com. "We've got a term here in the U.K. called 'greenwash,' when someone's trying to look green but you dig deeper [and] you see there's a lot of marketing behind it relating to their
image, but not so much substance in terms of reducing carbon footprints, carbon emissions or helping the environment. There's a lot of greenwash going on right now."

Green activist Leonardo DiCaprio reportedly flew his family from Paris to Rome on a private jet in 2006; he also reportedly declined a journalist's challenge that he never fly private again, though he has vowed to fly commercial as much as possible. Ken Sunshine, who represents Leo, recently told the New York Post's Page Six gossip column, "No star at his level flies commercial planes more than he does."

The Leonardo DiCaprio Foundation has fostered awareness of environmental issues through participation with such organizations as Natural Resources Defense Council, Global Green USA and the International Fund For Animal Welfare, according to DiCaprio's Web site. Representatives for the actor did not return requests for comment.

Green activist Brad Pitt still jets around with partner Angelina Jolie, according to published reports — recent trips include Los Angeles to New York round trip (carbon footprint: 1.814 tons), Chicago to Los Angeles one-way (carbon footprint: .798 tons) and from Los Angeles to Namibia (carbon footprint: 3.569 tons).

Pitt is working to help rebuild New Orleans’ Hurricane Katrina-ravaged Lower Ninth Ward with environmentally sound houses; his manager did not return a request for comment.

John Travolta was branded the ultimate hypocrite when the actor (and pilot) publicly spoke out about the need for alternative fuel, and then was reportedly found to be stashing five airplanes in his own backyard. His representative declined to comment, but said that Travolta owns two airplanes and has never owned five.

If the frequent use of private jets negates the impact of driving a Prius, flying your hybrid home from halfway around the world is also unwise — just ask Paul McCartney. The former Beatle-turned-environmental activist created an uproar within the environmental community when he had a new Lexus 600h flown to him in England from Japan via cargo plane rather than having it sent by ship.

"It's like driving the car 300 times around the world," said Gary Rumbold of co2balance, an international company that works with businesses and individuals to reduce carbon emissions. It was not clear if McCartney knew the vehicle would be sent to him via air freight rather than by ship.

Former Live Earth spokeswoman Madonna is one of the worst offenders, Buckley says — but that's not entirely her fault, considering her profession and the wattage of her star power. His calculation of Madonna's 2006 carbon footprint is about 1,018 tons — 651 tons from touring that year, mainly from flying on private jets.

But could the Material Girl really fly commercial?

"There are other high-profile people who fly business class and first class all the time — if they can do, it I'm sure Madonna can as well," Buckley said. "It's not like she's going to get mugged or anything."

Madonna’s representative did not return requests for comment.

Maybe Madge doesn't have to start slumming with the rest of us just yet; she could follow in the carbon footsteps of another gal on the road: Kelly Clarkson. The first "American Idol" winner is going green and running her tour on a blend of biodiesel to be supplied by Reverb, a non-profit focused on environmental sustainability among musicians.

Perhaps Clarkson should also have a chat with Mary-Kate Olsen. The former "Full House" star recently hosted a dinner party organized by the Environmental Media Association (a group that works to make the entertainment industry greener) during which her guests — among them, Mischa Barton and Nicole Richie — discussed sustainable living techniques. But Olsen also wears fur, and according to PETA, it takes 20 to 60 times as much energy to produce a fur coat from ranch-raised animals than it does to produce a fake fur.

Green actress Natalie Portman also has been called a hypocrite for using synthetic materials in her vegan line of footwear. But some rush to her defense.

"What Natalie Portman is doing with her shoes, even if they're not as green enough as they could be, she's saying she's concerned enough to try and maybe other people will try too," Environmental Media Association President Debbie Levin said. "Nobody's perfect. If you have to be perfect, you have an environmental crowd of like three people," she added.

At the recent Down to Earth party in New York thrown by Women's Heath magazine, host and eco-celeb Chloe Sevigny told FOXNews.com she was raised "green," so she hopes Hollywood is helping to spread the word.

"My mother was very earth-conscious and she raised me to be the way I am, and I think a lot of people were never taught that. And if we can raise awareness in any way, I think it's good," she said.

Buckley agrees — but only if stars walk the walk when they talk the talk.

"Obviously it's great that these celebrities are helping to inform the public and they carry a great weight," he said. "But if they are running around in private jets, that can easily negate all that."