The veteran BBC presenter stated: "We are a plague on the Earth. It's coming home to roost over the next 50 years or so. It's not just climate change; it's sheer space, places to grow food for this enormous horde."
Talking to the Radio Times, Attenborough warned: "Either we limit our population growth or the natural world will do it for us, and the natural world is doing it for us right now.
"We keep putting on programmes about famine in Ethiopia; that's what's happening. Too many people there. They can't support themselves – and it's not an inhuman thing to say. It's the case.
"Until humanity manages to sort itself out and get a co-ordinated view about the planet it's going to get worse and worse."
Viewed by many as a British 'national treasure' after a television career that spans seven decades from the 1950s, the 86-year-old's latest series David Attenborough's Natural Curiosities starts next week on the Eden channel.
Best known for his BBC Life series, the natural history broadcaster is reportedly the only person to have won a BAFTA in black-and-white, colour, HD and 3D.
Watch Digital Spy's interview with David Attenborough:
David Attenborough's Natural Curiosities airs from Tuesday, January 29 at 8pm on Eden.