Sir David Attenborough said the future of humanity depends on state leaders giving their “full backing” to environmental issues which he believes the King will do.
The broadcaster and naturalist, who turns 97 on Monday, appeared on BBC One with Kirsty Young as part of its coverage ahead of the King’s coronation on Saturday.
Sir David said Charles “very clearly” understood the relationship and importance of the natural world “right from being a small child”.
He said: “When he became prominent and an adult, he took a strong line at a time when nature conservation was regarded as being slightly specialist.
“But he realised what it was about and he was mocked actually, because he said ‘trees are so important I feel like talking to trees’.
“But in fact, he was absolutely right and the world has come to see the world as he saw it.”
He continued: “The fact is 20 or 30 years ago, it really was sort of oddball to a lot of people.
“But now everybody realises that the future of humanity is dependent upon a healthy natural world.
“The way ahead demands that leaders of the state should actually give their full backing and I’m quite sure that as King he will lead this country in a very important way.”
Sir David said Prince Philip, the late Duke of Edinburgh, was “very vigorous in ordering conservation”, adding: “I’m quite sure King Charles will be the same.”
He also spoke about first meeting the then-Prince Charles when he visited the BBC studios at the age of nine and held his pet cockatoo named Cocky.
“I had just come back from New Guinea with a load of animals which were going to the London Zoo, but I had a pet cockatoo and I was asked to bring it to the studios, which I did,” he said.
“Dear little Cocky is sitting on his (Charles’s) hand but in fact they have a very powerful beak and a very powerful bite and although I was fairly confident about Cocky, he could actually have removed his little finger.
“But all was well and it was a very happy occasion.”
Speaking about the coronation on Saturday, Sir David said he was looking forward to the “whole panoply of the military, the parade, and, of course, the ceremony itself” which he said will be “deeply moving”.