One day after Star Trek actor William Shatner became the oldest person to go to space, traveling aboard Amazon founder Jeff Bezos‘ Blue Origin rocket and capsule, Prince William criticized those using their billions to leave the planet. 

“We’ve seen everyone trying to get space tourism going … 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,” said the 39-year-old duke.

On July 11, English business magnate Richard Branson became the first of the so-called space billionaires to fly the VSS Unity, part of the Virgin Galactic fleet, to space. Less than two weeks later, on July 20, Jeff Bezos’ New Shepard rocket followed suit before completing its second trip on October 13. 

Related: Bill Gates Delivers ‘Classiest Burn’ to Billionaires Trying to Go to Space

Following his Thursday trip to space, Shatner said he was “struck by the fragility” of this planet and that “we all need to clean up this act now.” 

In the past, the actor dismissed concerns around billionaires Bezos, Elon Musk and Branson investing their vast fortunes in space travel instead of in social causes. “It’s their money,” he told NBC News in a July interview. “They can do what they want with it.”

But the duke told BBC that taking off to space isn’t a real solution, just a sign of “giving up.” 

William and other members of the royal family, including his father Prince Charles, have pursued an active environmental agenda as part of their royal duties. 

William says his father’s decades of environmental work have been challenging. “It’s been a hard road for him,” William told the BBC. “He’s had a really rough ride on that, and I think he’s been proven to being well ahead of the curve.”

The duke hopes his own son Prince George isn’t talking about saving the planet in 30 years, as that would be “an absolute disaster.”

Related: Jeff Bezos’ Blue Origin Employees Are Leaving the Company

William is behind the Earthshot Prize, which strives to solve planetary issues via new technologies or policies. The first five winners will be announced in a ceremony on Sunday; each will recieve $1.4 million. 

At the end of the month, world leaders, including the duke’s grandmother Queen Elizabeth, will assemble for the 2021 United Nations Climate Change Conference in Glasglow, Scotland. 

Although the conference is considered a critical move in the right direction by many, on Thursday U.S. climate envoy John Kerry told The Associated Press that discussions will likely end with nations still not meeting their goals for emissions cuts.