Prince Harry backed eco-campaigner and hit out at climate change deniers during a passionate rallying call, warning"no one can deny science".
The Duke of Sussex is in Botswana for the second leg of his Africa Royal Tour , having left wife Meghan Markle and little Archie behind in South Africa.
The Duke of Sussex will spend the next five days visiting organisations and charities in Botswana, Angola, Malawi before heading to Johannesburg where he will be reunited with his family.
On the first day of his solo trip, Harry visited Chobe Tree Reserve where he stressed saving the environment is a race against time, adding: "Led by Greta, the world's children are striking."
The Duke said he could not understand why anyone - "you, us, children, leaders" could ignore the facts from the last four decades.
The Duke started the day by helping a group of men get a 10-metre tree into the ground as he took part in the ultimate planting ceremony.
He clearly enjoyed the challenge of helping to create a new forest habitat on the banks of Botswana's Chobe River.
After decades of deforestation from locals gathering firewood and elephant activity, a conservation organisation working with locals is trying to create a nature and cultural park for the community.
The Duke got stuck in trying to plant the tree and worked with a group of men to push it upright before packing it with soil.
When he saw the huge mound of earth that needed to go into the hole, he smiled and joked: "How long do we have?"
Harry later joined young schoolchildren planting mahogany trees, crouching down with one young child to help him pack the sandy soil around the tiny sapling and at the end he high-fived the youngster to celebrate.
When he first arrived he was hugged by his friend Dr Mike Chase, conservationist and founder of Elephant Without Borders, which is working with a local organisation to develop the site into a nature and cultural reserve.
The land was privately owned but has been pledged to the local community and Dr Chase's organisation will manage it with the aim of creating a thriving riverbank forest.
After planting the large Baobab tree, Harry was the centre of a performance where he was feted and praised by a group of Sentebale Let Youth Lead advocates.
The youth leaders, from the duke's Sentebale charity which supports young people living with HIV, recreated a confidence boosting activity from camps staged in Botswana to support youngsters with the virus.
Called super camper, children are praised to boost their confidence using singing and dancing.
Harry laughed as one young advocate gave a poem-style tribute to him.
To smiles and laughter from dozens of young leaders, the young man said: "You make us feel like royalty.
"You left baby Archie and his mother to come and spend time with us, we appreciate you and love you."
The duke then sat down with the young advocates to listen to issues they wanted to raise at a health centre in Kasane.
It's the fourth day of the Sussexes' Royal Tour, and the trip has already been packed with fun events, powerful speeches and exciting photo ops.
The Sussexes carried out their first official engagement as a three yesterday morning, when Meghan and Harry took Archie to meet Archbishop Desmond Tutu - delighted fans with gorgeous photos and video of the royal tot.
Just a few hours after touching town at Cape Town airport, the couple headed to township Nyanga - known as the country's 'murder capital' - to learn more about Justice Desk.
The human rights organisation supported by the Queen's Commonwealth Trust, and Meghan and Harry spent the afternoon learning about what they do and chatting to members of the community.
As well as watching performances from local people and having a quick dance with women dressed in traditional costume, Meghan and Harry both gave moving speeches .
Meghan praised the work the organisation has been doing, and said she was visiting on a personal level as well as in her role as a member of the Royal Family.
She said: "I want you to know that for me I am here with you as a mother, as a wife, as a woman, as a woman of colour and as your sister."
They later went on a tour of the District Six Museum to learn about their work to reunite members of the community forcibly relocated during the apartheid era, before joining a community cooking activity with former residents at the nearby Homecoming Centre.
On day two they chanted and danced with surfers on Monwabisi beach to learn more about Waves for Change, a charity which helps vulnerable young people living in challenging communities through surfing.
They exchanged parenting compliments, with Meghan saying Harry was the "best dad" and said it was a new strength they were "learning and developing".
Later in the day they headed to Auwal Mosque, the oldest in the country, and Meghan wore a headscarf to meet leaders from different faiths.
Yesterday the couple gave the world the first official glimpse of Archie, taking him to meet Archbishop Desmond Tutu and his family.
The veteran Nobel Peace Prize winner, who used the pulpit to preach against the injustices of white minority rule during apartheid, was completely charmed by the little royal.
During their meeting Meghan and the Archbishop’s daughter Thandeka Tutu Gxashe joked that Archie would have have to get used the the cameras in his life .
Thandeka said “I have cameras in my genes.” Meghan replied, “He’s an old soul”
Harry said, “I think he is used to it already”.
The Archbishop’s daughter also joked, “You like the ladies. He’s going to be a ladies man”
Speaking to Archbishop Tutu about Archie, Harry said: "For me it's the responsibility that we all have to try and make their lives better, however we can."
