BOSTON — The Prince and Princess of Wales embarked Wednesday on their first overseas trip since the death of Queen Elizabeth II, aiming to showcase the younger face of a monarchy that is tackling important issues like climate change as it attempts to remain relevant in a modern, multicultural Britain.

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The three-day trip to Boston is focused on Prince William’s splashy initiative to award millions of dollars to a new generation of environmental entrepreneurs who are developing everything from cleaner burning stoves to alternatives to leather. It will include visits to a program for at-risk youth, a sustainability lab and a tour of Boston’s shoreline to see the city’s effort to combat climate change.

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It will culminate Friday in the awarding of the prince’s signature Earthshot Prize, a global competition aimed at finding new ways to protect the planet and tackle climate change.

After their arrival, the beaming royal couple strolled onto a stage at City Hall Plaza — William wearing a single-vent navy suit and Kate radiant in a Burberry dress and Alexander McQueen coat, and earrings by designer Shyla London — amid tight security and a cheering crowd, many snapping photos and video.

Prince William told the crowd that one of President John F. Kennedy’s speeches was the inspiration to hold the second Earthshot Prize in Boston.

“It was that moonshot speech that inspired me to launch the Earthshot Prize with the aim of doing the same for climate change as President Kennedy did for the space race. And where better to hold this year’s awards ceremony than in President Kennedy’s hometown,” William said.

Later, the couple sat courtside for a Boston Celtics-Miami Heat game, joined by team managing partner Wyc Grousbeck, co-owner and president Steve Pagliuca and his wife, Judy, along with Boston Mayor Michelle Wu and Massachusetts Gov.-elect Maura Healey.

The royal couple was announced to a cheering Garden crowd during a timeout in the second quarter and briefly shown on the video screen. But a security official stepped in front of the camera, eliciting a chorus of boos.

The visit comes less than three months after the death of Queen Elizabeth, whose personal popularity dampened criticism of the crown during her 70-year reign. King Charles III, William’s father, has made clear that his will be a slimmed-down monarchy, with less pomp and ceremony than its predecessors.

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“I think this is less about saving the Earth and more about saving the royal family,’’ said Boston University professor Arianne Chernock, an expert in modern British history. “To be honest, we’ve seen Charles as king and his first months in that position trying to feel his way, find his way towards being a more relevant, more modern monarch. And I think we see something similar happening with William and Kate.’’

Part of that reset involves reclaiming the hearts and minds of people in America, where William’s younger brother, Prince Harry, and sister-in-law, Meghan, have dominated the media since moving to California in 2020. Harry and Meghan have criticized the royal family for alleged racism and insensitive treatment and built their own media profile by making films and podcasts for Netflix and Spotify.

The Netflix series “The Crown” has also resurrected some of the more troubled times of the House of Windsor, including the collapse of Charles’ marriage to the late Princess Diana, William’s mother, amid mutual allegations of infidelity.

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But William and Kate are keen to tell a different story, about their work on environmental issues, mental health and early childhood education.

During a gala concert celebrating the queen’s Platinum Jubilee in June, William delivered a speech highlighting his grandmother’s and father’s pioneering work on the environment, as images of jungles and oceans were projected on the walls of Buckingham Palace behind him.

Kate last week wrote an opinion piece on the need to improve the lives of young children that appeared in The Daily Telegraph, one of Britain’s most influential newspapers, alongside a photo of the princess sitting cross-legged among a group of elementary school students.

William and Kate’s last visit to the United States was in 2014, not long after their wedding. During that trip, the glamorous young couple were feted as they toured the eastern U.S. Eight years later, now in their 40s and with three young children, the prince and princess are finally having a return engagement.

On Wednesday, they were greeted at the airport by Massachusetts Gov. Charlie Baker before heading to City Hall to meet Mayor Wu and Gov.-elect Healy ahead of a visit to the John F. Kennedy Memorial Library and Museum. President Joe Biden planned to greet the couple later in the week.

City Hall, along with 15 other landmarks, was lit up in green to mark the kickoff of the Earthshot celebrations.

Andrew Warburton, who grew up in Bristol, England, praised their environmental work while waiting for the event. “They represent the future in that way,” he said.

Pamela Spencer, a school teacher, waited with her two sisters in hopes of giving William and Kate a bouquet of flowers.

“They are following in the footsteps of her late majesty. I’m really here to show them they have a lot of support in New England,” Spencer said.

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On Thursday, William and Kate will visit Roca Inc., highlighting the racial equity group’s efforts to improve the lives of young people by addressing issues such as poverty, incarceration and trauma from urban violence. They will also visit Harvard University’s Center on the Developing Child, a leader in research into the long-term impact of early childhood experiences.

But throughout the trip, William’s eye will be on the Earthshot Prize.

The ability of the royals to shine a light on the issue and fuse their fame with entertainers such as Billie Eilish, who is set to headline the awards show, is likely to make people pay attention.

Earthshot offers 1 million pounds ($1.2 million) in prize money to each of the winners of five separate categories: nature protection, clean air, ocean revival, waste elimination and climate change. The winners and all 15 finalists also receive help in expanding their projects to meet global demand.

The winners are set to be announced Friday at Boston’s MGM Music Hall as part of a glitzy show headlined by Eilish, Annie Lennox, Ellie Goulding and Chloe x Halle. The show will also feature videos narrated by naturalist David Attenborough and actor Cate Blanchett.

— Kirka reported from London. Associated Press Sports Writer Kyle Hightower contributed to this report.