The Duchess of Cambridge called for action to save the planet in a confident speech at the first-ever Earthshot Prize awards ceremony on Sunday evening.
Kate presented the final award of the night to the Republic of Costa Rica, in the category Protect and Restore Nature.
MORE: Why Kate Middleton really wore a 2011 recycled gown for Prince William's Earthshot Prize
Speaking directly to a global audience of millions, the Duchess said: "Nature is vital to us all. A thriving natural world regulates our climate, nurtures our physical and mental health and helps feed our families.
"But for too long we’ve neglected our wild spaces and now we’re facing a number of tipping points."
WATCH: The Duchess of Cambridge presents an award for Earthshot 2021
"If we don’t act now, we will permanently destabilise our planet and we will rob our children of the future they deserve. Our Earthshot Prize Finalists show us however that we can, by 2030, see the natural world growing, not shrinking, for the first time in centuries."
READ: Prince William and Kate Middleton's touching meeting revealed and it links to a royal tour
SEE: 16 unbelievable royal living rooms: Kate Middleton, Princess Anne and more
Kate, who looked stunning in a ten-year-old lilac Alexander McQueen gown she first wore to a Bafta event in Los Angeles in 2011, listed the three finalists before announcing the winner.
Prince William launched the Earthshot Prize to find innovative environmental initiatives
She said: “The Pole Pole Foundation in the Democratic Republic of Congo shows how communities can take a stand to protect wildlife, whilst feeding their people.
"The Republic of Costa Rica has provided an example for the world that deforestation can be turned around, whilst growing your economy.
"And Restor from Switzerland is using technology to unite people all over the planet to protect the environment."
The Duchess, who has in the past been a nervous public speaker, delivered a polished performance to an audience of around 100 people in the East Court Theatre of Alexandra Palace, concluding: "I am delighted to announce that the first-ever Earth Shot Prize to protect and restore nature is awarded to the Republic of Costa Rica."
The award was accepted by the country's leader, President Carlos Alvarado Quesada, who appeared via video call with his wife Claudia and son Gabriel.
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity, royal and lifestyle news delivered directly to your inbox.