The green Oscars: A Hollywood blockbuster starring DiCaprio and Cruz

Things have truly changed in Hollywood since Kermit the Frog famously lamented that it was "not easy being green".

Now an entire ecosystem of Hollywood big beasts is vying to outdo each other in ecological correctness. And they are strutting their sustainable stuff in their favoured habitats - star-studded parties and gigs.

On Wednesday, a glittering group of green greats - headed by Leonardo DiCaprio, Penelope Cruz, Salma Hayek and Edward Norton - will roll up to the hot-spot Avalon club to kick off the Oscar season.

But since this is all about the environment, they will be stepping out of hybrid cars rather than limousines, and sipping "exclusively organic and sustainable wine, beer and cocktails" to the accompaniment of the music of the Los Angeles band Maroon 5.

The Global Green Pre-Oscar Party is the latest of a series of biodegradable bashes and initiatives. Last month, there was a "Golden Green" evening, with another clutch of celebrities, to mark the Golden Globe awards - and a new campaign, Global Cool, which, with still more famous faces, launched its 10-year journey to defeat global warmingand make environmentally friendly living "aspirational".

And on Friday, Cameron Diaz and Al Gore announced a series of Live Earth rock concerts in London's Wembley Stadium, and around the globe, to highlight the dangers of global warming. More than 100 of Hollywood's favourite musicians - including the Red Hot Chili Peppers, Snoop Dogg, Sheryl Crow and Lenny Kravitz - will take part in an extravaganza billed to far exceed 2005's Live8.

Wednesday's party - put on by the American branch of an environmental pressure group founded by the unlikely figure of Mikhail Gorbachev, the former Soviet leader, in 1993 - similarly aims to raise funds and awareness for "smart global warming solutions". For the past five years Global Green has been persuading celebrities to turn up to the Academy Awards in fuel-efficient vehicles rather than gas guzzlers. Morgan Freeman, Susan Saradon, Charlize Theron and Harrison Ford have all taken part in its Red Carpet/Green Cars Oscar campaign.

The party will raise money for "the green rebuilding of New Orleans", starting with an eco-friendly block of flats, the winning design of a competition it held under the chairmanship of Brad Pitt.

Debbie Levin, the president of the Environment Media Association, which has been working to green Hollywood for 18 years - adds: "People see celebrities as role models. We are showing that you can have just as elegant a lifestyle living green as you can without that consciousness.

"Our lifestyle choices can save the world."

She believes the message is getting through. In Hollywood itself, "some of the people who have not been involved in the past are now jumping on the bandwagon". And outside, "everyone is grasping hold of it and thinking that these Hollywood whackos are right".

She is, however, lukewarm about this week's party. She helped to host the Golden Green party - attended by Maggie Gyllenhaal, Sara Jessica Parker, Rachel Weisz , Eva Longoria and Paris Hilton - which she insists was greener.

It was held in a former department store being turned into a green block of flats, set in a landscape of plants and flowers, with recycled paper decorations and tables made of reclaimed wood.

The 'IoS' Green Carpet awards

Leading man

LEONARDO DICAPRIO

The grand young(ish) man of Hollywood environmentalism, active in green causes since childhood. Started an environmental foundation nine years ago and even has his own campaigning website. Now working on a feature-length documentary on the global environment called 11th Hour.

Leading lady

CAMERON DIAZ

Took on green issues in Hollywood long before they became fashionable. Was one of the first stars to buy a hybrid car and promoted energy-efficient vehicles and energy-saving items in a series of advertisements with Gwyneth Paltrow. Presents a series on environmentally friendly travel for MTV.

Most promising newcomer

AL GORE

The former vice-president, up for two real Oscars, was once a byword for wooden delivery. He is this year's unlikeliest film star, presenting his box-office success, An Inconvenient Truth. Unimpressive in addressing global warming while in office, he has now had a decisive influence in changing opinion.

Supporting actress

SALMA HAYEK

Brought up in the pollution hotspot of Coatzacoalcos, a petrol-refining centre on the Mexican coast, she has prompted a programme that persuades celebrities to install solar cells, and gives a set to a poor family every time it succeeds.

Lifetime achievement

HARRISON FORD

So green that he even has an ant named after him. Has served on the board of the campaigning wildlife group Conservation International for more than a decade.