Renowned naturalist David Attenborough sat down with BBC Newsnight for a wide-ranging interview about the environment and how the planet cannot accommodate the "alarming rate" of human overpopulation.

"One of the reasons that the population has increased as fast as it has is that people like me are living longer than we did," Attenborough explained. "And so there are more and more people just because the expectancy of life has increased."

Even now, with the world's current population of 7.6 billion, humanity uses up Earth's natural resources 1.7 times faster than the planet's ecosystems can regenerate, according to the Global Footprint Network. This ecological debt is poised to increase as the world population is expected to reach 8.5 billion by 2030, 9.7 billion in 2050 and 11.2 billion in 2100, the United Nations projected.

As Attenborough noted, "In the long run, population growth has to come to an end."

The legendary English broadcaster, who spoke with the BBC on the 40th anniversary of his groundbreaking Life On Earth series, commented on a variety of environmental topics. He said he's eating much less meat: "We simply cannot destroy the natural forests and plains of the world in order to feed ourselves. We have to modify our diet." On the growing issue of plastic pollution, he said, "We should do our best to avoid the use of plastic."

Also in the interview, Attenborough admitted that up to five years ago he was "very, very pessimistic" about the future of the planet, but the landmark Paris agreement to combat climate change changed his attitude.

"The Paris agreement seemed at the time to be at last nations coming to their senses," he said.

Attenborough remains hopeful despite President Donald Trump's intention to withdraw from the international accord signed by nearly 200 countries.

"It is true that President Trump doesn't go along with it. To what extent the United States is going to withdraw from it, we'll see," he said. "My suspicion is that people will realize that actually the United States' attitude is outdated, it doesn't apply anymore, and I think that will be overcome.

"There's a groundswell internationally of recognizing what we are doing to the planet and the disaster that awaits unless we do something," Attenborough said. "This is the only world we've got."