Prince Harry backed teenage activist Greta Thunberg on Thursday as he declared the world was in a state of “emergency” and “losing'” the battle against climate change.

He then helped to plant a tree by the banks of Botswana’s Chobe River to record his visit and chided climate change deniers, saying: “No-one can deny science.”

The Duke stressed saving the environment was a race against time, adding the world should look to young people like Greta Thunberg for inspiration and guidance: “Led by Greta, the world’s children are striking.”

He went on to say there had been scientific evidence of climate change for at least 30 years, “And it’s only getting stronger and stronger,” he added, according to the BBC.

He said he could not understand why anyone – “you, us, children, leaders” could ignore what has happened over the past 40 years, and acknowledged how Bostwana offered him a place to escape to following the death of his mother, Diana, Princess of Wales. He said:

Fifteen years I’ve been coming here, it’s a sense of escapism, a real sense of purpose … I have some of my closest friends here over the years. I came here in 1997 or 1998 straight after my mum died, so it was a nice place to get away from it all. I feel deeply connected to this place and to Africa.

Prince Harry and the Duchess of Sussex, Meghan Markle, arrived in Africa on Monday to spread their climate advocacy to a new audience.

Baby Archie has joined them on the flying 10-day visit along with a team of 13 assistants including a “social media officer” and a hairdresser for Markle.

The Sussexes’ first tour as a family comes after the duke and duchess flew to Rome to watch Meghan’s close friend, fashion designer Misha Nonoo walk down the aisle with oil tycoon Michael Hess on Friday.

Highlights of the latest trip will see the pair visit a township in Cape Town to tour a workshop supporting children and young girls, and visit another near Johannesburg where they will learn about a project tackling rising unemployment. Malawai, Botswana, and Angola are also on the itinerary.

Barefoot Prince Harry Warns World: Climate Change Must Be Addressed https://t.co/9q7Zkbfqau — Breitbart London (@BreitbartLondon) August 1, 2019

The past two months have been busy for the Royal pair, with them spotted at one stage taking four private jet flights in just 11 days as they criss-cross the globe. Their seemingly constant air travel has not been without controversy.

Last month a barefoot duke stood before an elite audience of business leaders and celebrities gathered at Google’s annual deluxe retreat in Sicily to warn immediate action is needed to avoid an approaching climate catastrophe.

He spoke ahead of the Duchess of Sussex’s last-minute dash to New York two weeks ago to watch her friend Serena Williams play in the U.S. Open tennis final.

That trip came in the same week Prince Harry flew to Amsterdam to caution holidaymakers and tourism chiefs about the damage being done to the environment by frequent flyers.

The prince has already announced he and the duchess will have no more than two children because of the concerns they share for the environment.