Sir David Attenborough and Greta Thunberg came together for the first time today (October 21) during a world-renowned Bristol event.
The two environmental figureheads took part in a 30-minute virtual chat as part of Wildscreen Festival 2020.
During the event, Sir David told Greta the 'The world owes you a lot'.
The BBC broadcaster also voiced his fears that the coronavirus pandemic had diverted attention away from the climate crisis.
The 94-year-old said several international climate conferences had been cancelled because of Covid-19.
"I am worried that people will take their eyes off the environmental issue because of the immediate problems they have on Covid-19," he said.
Over the decades, he said the 'urban world' had been taking a lot from the natural world.
"We have a big debt to other countries," he said. "We have been taking their stuff and now its time we pay it back."
He said politicians should no longer be thinking about profit margins when they attend summits, but whether they are making the world a better place.
And voters need to think in a similar way when they are picking their leaders, he said.
Greta said everyone needs to be taking action now, by campaigning, reducing their own carbon footprint and lobbying their politicians.
She said: "We don't have enough time, or carbon budget left to argue 'this is better than this'.
"Everything that we possibly can, we need to do.
"The most important thing is to try and understand the problem - try to educate yourself, read up on it and spread that information to others.
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"If enough people become aware and if enough people put enough pressure on people in power and the elected officials then they will have to do something because the politicians job is to get elected and to do as the voters ask."
She also praised Sir David's A Life On Our Planet for the way it "connected all these issues, like the climate crisis, loss of biodiversity, loss of soil and over-fishing".
