Sir David Attenborough has said that a “frightening explosion in human numbers” was behind every threat to wildlife across the world.
The veteran broadcaster made his comments as he became patron of a group seeking to cut the growth in human population.
The Optimum Population Trust (OPT) believes Earth may not be able to support more than half its present numbers before the end of the century.
In a statement released on the organisation’s website, Sir David, 82, said: “I’ve seen wildlife under mounting human pressure all over the world and it’s not just from human economy or technology – behind every threat is the frightening explosion in human numbers.
“I’ve never seen a problem that wouldn’t be easier to solve with fewer people, or harder, and ultimately impossible, with more.
“That’s why I support the OPT, and I wish the environmental NGOs would follow their lead, and spell out this central problem loud and clear.”
World population is projected to rise from 6.8 billion today to 9.1 billion in 2050, it says.
OPT chairman Roger Martin said he was “delighted” to welcome Sir David as patron and added: “All serious environmentalists know perfectly well that population growth, exploding in the 20th century, has been a key driver of every environmental problem.
In January, Sir David revealed he received hate mail from viewers for not crediting God in his nature programmes.
His latest documentary on Charles Darwin and natural selection marked two centuries since Darwin’s birth and 150 years since the groundbreaking On the Origin of Species was published.