The Cannes Film Festival has vowed to go green, even trimming its red carpet in half -- but can it make any difference to an industry built around private jets and rampant consumption?

Movie stars from Leonardo DiCaprio to Juliette Binoche have made environmental campaigning a central part of their image in recent years, fronting movies about climate change and using their soapboxes to call for action.

Keen to show support, the organisers of Cannes, which runs from July 6 to 17, have said the environmental "emergency is at the heart of its concerns" this year. 

They have banned plastic bottles, deployed a fleet of electric cars, and organised a special programme of climate-focused films. 

Perhaps most symbolic of all, the festival is cutting the volume of its red carpet by 50 percent, and making it from recycled materials rather than the usual PVC. 

But the film industry, with its non-stop, continent-skipping circus of premieres and parties, is far from getting any gold stars from Greta. 

DiCaprio, for instance, famously pulled off an 8,000-mile round trip in a private jet in 2016 to pick up an environmental award. 

Cannes finds itself in an awkward position -- hosting movies about climate change followed by massive parties that generate tonnes of waste and relying heavily on people flying in from all over the world. 

This year, it hopes to offset some of that carbon footprint with a 20-euro contribution from each participant to be disbursed by "a scientific committee of experts". 

But the organisers admit film festivals are "an environmental challenge" that cannot be addressed overnight. 

- 'Epochal change' -
"There is a monstrous job to do" but the efforts are "very encouraging," said French filmmaker and activist Cyril Dion. 

He is showing his new documentary "Animal", about the threat to global biodiversity, as part of the environmental programme this year. 

The festival "is sending a signal that all the others should follow," he said. "These measures reflect an epochal change for cinema."

There are signs of change elsewhere in the industry. The Berlin Film Festival's red carpet is made from recycled fishing nets.

In France more broadly, film subsidies will be conditional on sustainability commitments from 2024.

But with the signs of crisis mounting, is it still acceptable to gather people from around the globe for a festival? 

"There is really a change of mindset," said Carole Scotta, head of French production firm Haut et Court and a leading voice in the climate debate. 

"But it's complicated for Cannes, which has to maintain a certain amount of festivity as the leading festival in the world," she said. "We can't show up in flip-flops."

From Cannes to Venice to Sundance to Berlin, Scotta recognises that the merry-go-round of festivals is "not good for the planet", while the pandemic has shown that digital alternatives are possible. 

The film industry has a certain "schizophrenia" on the issue, said Simon Valensi, of The Shift Project, a French think-tank pushing for a post-carbon economy.

"If we want to respect the Paris climate accords on carbon neutrality by 2050, sooner or later the emissions created by big festivals will have to be put in question," Valensi said.

But he added that despite the modest scale of the efforts so far, "it's already a major revolution that the festival is thinking about its economic impact."

74th Cannes Film Festival in numbers
Here are a few numbers related to the 74th edition of the Cannes Film Festival, which runs from July 6 to 17:

- Five -
The number of times the festival has not gone ahead: in 1939 due to the Second World War, in 1948 and 1950 for financial reasons, in 1968 due to protests across France and in 2020 due to the coronavirus pandemic. 

- Eight -
The number of directors or co-directors who have won the Palme d'Or twice: Francis Ford Coppola, Shohei Imamura, Ken Loach, Bille August, Emir Kusturica, the Dardenne brothers, Michael Haneke and Alf Sjoberg.

- 19 -
The number of 18-carat-gold leaves that make up the palm of the trophy. Worth 20,000 euros ($23,700), it is made by Swiss jeweller Chopard.

- 20 - 
The contribution in euros requested from each attendee this year for the first time to offset the festival's carbon footprint, as the organisers seek to make environmental concerns a central part of the event. The money will be distributed by an independent panel of experts. 

- 24 -
The number of films in competition this year. That is up on recent years but there have been more in the past. The inaugural edition in 1944 saw 44 feature films competing. 

Twenty-four is also the number of steps leading up to the Palais des Festivals, nicknamed the "steps of glory" in France.

- 20,000,000 -
The budget in euros for organising this year's festival. Half comes from national and local authorities, and the rest from sponsors.