UNITED STATES, WASHINGTON - Actress Sigourney Weaver warned of the dangers facing oceans, President Barack Obama threw a White House party, and UN chief Ban Ki-moon urged the world to kick the carbon habit -- all in honor of planet Earth.
They were part of a galaxy of stars from the political, show business and sports worlds who shone the spotlight on Mother Nature as the United States marked the 40th anniversary of Earth Day on Thursday.
At a White House reception, Obama called Earth Day "a bright moment in our nation's history and a milestone in the ongoing fight to protect our environment."
Earth Day was "created" in 1970 by Gaylord Nelson, a senator from Wisconsin, and Dennis Hayes, then a young graduate student.
"Together, they raised their voices and called on every American to take action on behalf of our environment," Obama said.
"And in the four decades since, millions of Americans have heeded that call and joined together to protect the planet. And we've made immense progress since that day, from the landmark legislation of the 1970s, the Clean Air and the Clean Water Act, to the conservation of America's precious landscapes," he said.
Weaver took a lead role in the Earth Day celebrations, testifying before a Senate subcommittee alongside a fisherman, a diver and two scientists about how carbon emissions are turning the world's oceans into acid baths.
"I've done enough science fiction to know that our Earth will survive through various nightmare scenarios," said Weaver.
"But that's entertainment. This is real and as citizens we have to act now so that we are able to look into our children's eyes in 20 years and say we did the right thing when we had to," she said.
In James Cameron's blockbuster movie "Avatar," Weaver plays a scientist working on the distant planet Pandora, where the Na'Vi people have to fight off strip-miners from Earth after a precious mineral called unobtainium.
New York City threw a big party for the 40th anniversary of Earth Day in Times Square, where UN Secretary General Ban Ki-moon urged Americans to "show the way, at home and abroad... show the world that we can kick the carbon habit."
During its 40 years of existence, Earth Day "has helped create a sense of shared responsibility for our environment and our one and only home," Ban said.
"Millions of Americans and people around the world are reducing their carbon footprint, recycling, planting trees... and pushing for policies that have brought cleaner rivers and skies," he said.
Auction house Christies will Thursday evening hold an auction in New York to raise funds for four non-profit organizations that promote environmental projects and stewardship.
Among the lots on the auctioneer's block will be a round of golf with former president Bill Clinton, as well as offerings from tennis star John McEnroe and actresses Brooke Shields and Candice Bergen.
On the National Mall in Washington, volunteers in front of a tent where a very small scale version of the planet Pandora had been recreated with lush greenery, handed out packets of seeds for a "tree of life," the central source of energy for the Na'Vi in Avatar.
Cameron will be on the Mall on Sunday to call for Americans to plant one million trees as part of Earth Day, which is being celebrated over nine days in the US capital.
Also on Sunday, another galaxy of stars from the music world, including Sting, Bob Weir of the Grateful Dead and John Legend, will perform on the National Mall at a rally that thousands are expected to attend.
"It's great that the stars are coming out to shine a light on these causes," Donald Waters, a fisherman who testified on Capitol Hill with Weaver, told AFP.
"To a lot of people, having Sigourney Weaver here brings more of a spotlight onto the subject of ocean acidification.
"But to me, I'm more worried about my livelihood than I am about a superstar," he said.