The Duke of Cambridge has called on the focus of the "world's greatest brains" to be on "trying to repair this planet" rather than blasting off into space.
William criticised the modern space race and space tourism in an interview set to air the day after Star Trek’s William Shatner made history by becoming the oldest person in space.
The duke, who was interviewed about climate change ahead of his inaugural Earthshot Prize awards, said: "We need some of the world’s greatest brains and minds fixed on trying to repair this planet, not trying to find the next place to go and live."
The prize will see five winners awarded £1 million prizes for solutions to the planet’s environmental problems and will run until 2030.
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Speaking to BBC Newscast on BBC Sounds, William warned the Cop26 summit, where world leaders will gather in Glasgow at the end of the month, against “clever speak, clever words but not enough action”.
“I think for COP to communicate very clearly and very honestly what the problems are and what the solutions are going to be, is critical,” he said.
“We can’t have more clever speak, clever words but not enough action.”
The duke expressed his concerns about a rise in climate anxiety in young people, and said it would be a “absolute disaster” if his eldest son, Prince George, was having to talk about the same issue in 30 years time when it was too late.
“We are seeing a rise in climate anxiety. You know, people, young people now are growing up where their futures are basically threatened the whole time," he said.
“It’s very unnerving and it’s very, you know, anxiety making".
William added that his father the Prince of Wales, who is known for his long-standing commitment to green issues, had a “really rough ride” when he first started talking about climate change.
The duke also said it was his late grandfather the Duke of Edinburgh had started the royal interest in environmental issues.
Prince Charles takes his fight to help save the planet to the world's biggest polluter
William said of his father Charles: “It’s been a hard road for him. My grandfather started off helping out WWF a long time ago with its nature work and biodiversity, and I think that my father’s sort of progressed that on and talked about climate change a lot more, very early on, before anyone else thought it was a topic.
“So yes, he’s had a really rough ride on that, and I think you know he’s been proven to being well ahead of the curve.
“Well beyond his time in warning about some of these dangers.
“But it shouldn’t be that there’s a third generation now coming along having to ramp it up even more.
“And you know, for me, it would be an absolute disaster if George is sat here talking to you or your successor, Adam, you know in like 30 years’ time, whatever, still saying the same thing, because by then we will be too late.”
He added that his viewpoint had changed since he had his own children, saying: “I want the things that I’ve enjoyed – the outdoor life, nature, the environment – I want that to be there for my children, and not just my children but everyone else’s children.
“If we’re not careful we’re robbing from our children’s future through what we do now. And I think that’s not fair.”
William discussed his ambitious Earthshot Prize, saying it was about trying to create action.
William and the Duchess of Cambridge are attending the star-studded ceremony, hosted by Clara Amfo and Dermot O’Leary, at Alexandra Palace in London on Sunday.
“The prize itself will stimulate solutions and action that a lot of people haven’t necessarily produced yet, and so I’m hoping, you know, the prize will galvanise a lot of people in positions of responsibility to, you know, go further, bigger and actually start to deliver,” the duke said.