We'll preface this by saying that a lot of celebrities do great things for the environment. Ed Begley, Jr., has led the green charge for decades, followed by staunch supporters like Leonardo DiCaprio and Cameron Diaz. A few of the names on our list drive eco-friendly cars and spearhead events to help stop global warming.

But some have made huge missteps in the name of environmentalism. The Edge, guitarist from U2 (a band known for fighting the green fight), has caused a stir recently with a proposal to build five homes on his hilltop land in Malibu. Only time will tell if his construction project will be as environmentally sound as he claims or the eco-disaster that opponents fear. Other celebs don't even seem to try, like Simon Cowell, whose gas-guzzling car fleet and weekly roundtrips from London to L.A. leave him with a carbon footprint bigger than his massive ego.

This Earth Day, we celebrate the efforts of those working to better the planet. Environmental watchdog groups have been keeping track of which celebrities are doing their part — and which ones say they're green, but their extravagant lifestyles tell another story. Sure, it's not easy being green, but these stars make it look really easy to be brown.

Photo gallery: See the "brownest" celebrities.

Celine Dion's "Titanic” Water Use:

According to public records, the singer used 6.5 million gallons of water at her oceanfront Florida home in 2007 — and she wasn't even living in it. The house, then under construction, recorded a usage of approximately 65 times more than the average Florida resident. That much water could fill a bathtub every four minutes, or ten Olympic-sized pools. As far as we know, Celine’s only got two of those.

John Travolta's Jet-Fueled Lectures:

Travolta travels the world lecturing on global warming. Seems like a noble way for a celebrity to spend his off-hours. One small problem: He makes the trips in one of his five — yes, five — private planes. He talks about the importance of alternate fuels and reducing emissions, but his own carbon footprint is estimated to be about 800 tons per year, about 100 times more than the average person. He blames his use of jets on the nature of being an entertainer, which leaves us to wonder: Is his position as Ambassador to Qantas Airlines entertainment for us or him?

Elizabeth Hurley's Big Fat Indian Wedding:

Elizabeth's 2007 wedding to Arun Nayar must have been amazing. The six-day celebration took place in four cities on two continents, and the happy couple footed the bill and flew every guest to each event by private Lear jet, producing 200 tons of carbon dioxide! That's more than an average British couple can produce in ten years. Way to go, Liz!

David Beckham's Soccer Feet Leave a Big Footprint:

Posh and Becks were once christened London’s “First Couple.” For a while they claimed that title in the U.S. as well. But they also have a less honorable jewel in their "we're-better-than-you" crown: Most Environmentally Unfriendly Celebrity Pair. Becks alone flies 250,000 miles annually for matches and appearances, owns 15 gas-guzzling vehicles (including several SUVs), and has five homes. His carbon footprint is estimated at over 163 tons a year, compared to the American average of 7.8. You know what they say: big feet, big footprint.

Madonna's Bottled Water Habit:

In 2007 Madonna headlined the London leg of the Live Earth — Al Gore's answer to Live Aid — concert in an effort to raise awareness of global warming and promote environmental efforts worldwide. Gore and his staff even purchased carbon credits to offset the event’s carbon expense. But what about the rest of the year, Madge? Rumor has it the Material Girl chalked up 1,000 tons of carbon dioxide touring that year and spent over $100,000 on bottled water. That's a lot of plastic!

Barbra Streisand's Not-So-Evergreen Habits:

Barbra makes no bones about her environmentalism. Her Streisand Foundation supports green companies. She even donated $16 million from her 2006 tour to eco-friendly organizations and other charitable causes. So we ask then, Babs, why do you air-condition your 12,000-square-foot barn, use 120 bath-sized towels per performance, and water your lawn to the tune of $20,000 a year? Doesn't environmental charity begin at home?

Arnold Schwarzenegger's Carbon Commute:

Sure, he claims to be the anti-global-warming politician, and he even traded in his Hummers for some more eco-friendly cars. The only problem: Arnold hardly ever drives. In fact, he commutes 380 miles every day from Los Angeles to Sacramento by private jet. His mode of transport does more environmental damage in one hour than a small car does in a year. The California governor claims to offset his carbon dioxide with "pollution credits" (funding efforts to reduce greenhouse gases). You just can't plant enough trees to offset this kind of hypocrisy.

Tom Cruise's Flying Mini-Van

Eco-lobbyists have nicknamed the actor "emissions impossible," but it's all for the sake of keeping wife Katie Holmes happy. Cruise added one more private jet to his fleet (for a total of three) when he gave Katie a $20 million jet as a wedding gift in 2005. The couple allegedly uses these planes somewhat like family minivans, shuttling kids around the world, going on monthly shopping sprees, and popping in on the latest fashion shows. It’s been said that Tom’s even used the jet to pick up groceries, a rumor he hasn’t denied.

Paul McCartney, You Can Fly My Car

Sir Paul is pretty green. His environmental concerns are mainly concentrated on the benefits of vegetarianism (the meat industry is a major contributor to global warming). He even bought a hybrid vehicle to cut down on his personal footprint. But the ex-Beatle made just one minor misstep. He had the car specially flown from Japan, creating more emissions with one flight than the car will ever save in its lifetime. Nice try, Paul.

Woody Harrelson's Vegan Shoes and Belt

Some might suspect Woody of taking his environmental concern to the extreme. As a devoted vegan he uses as many vegan products as he can — vegan clothes, vegan shoes, even vegan toothbrushes. Yes, we said, “vegan toothbrushes.” Apparently, these items aren’t made from vegetables, as you might assume, but rather via processes that don’t use animal byproducts. Hard-core eco-fans believe it’s good for the animals, good for our health, and good for the planet. But Woody took his love for Mother Earth to new extremes at the 2008 Cannes Film Festival when he realized he’d forgotten his favorite vegan shoes and belt at his California home. Unable to find replacements, he had them flown in. Not sure the carbon footprint equals out here.

Photo gallery: See the greenest musicians at GetBack.com.