David Attenborough: Population cannot go on increasing
16 December 2013 Last updated at 10:20 GMT
In May 2013, Sir David Attenborough launched BBC Radio 4's Tweet of the Day - a few moments of birdsong and a bit of information about the bird in question.
During the interview about Tweet of the Day, speaking to the Today programme's Sarah Montague, he also voiced concern about worldwide overpopulation.
"We are such a densely populated country," he said.
"The world is only so big. You simply can't go on increasing forever, so something's going to stop it. Either we can stop it or the natural world will stop it for us."