What humans do over the next 50 years will determine the fate of all life on the planet.

Human beings, because we're so clever, have removed every single one of those population limiting factors... So nothing controls our increase in numbers except our own wish. Since I first started making television programs, the population of the world has increased three times. That's an extraordinary notion. Can it increase four times? Can it increase five times? The Earth is a finite size. So a point will eventually come when we run out of food, when we run out of space and when we will have destroyed most of the natural world. So ought we to do something about it before that happens?

I think a major element of jetlag is psychological. Nobody ever tells me what time it is at home.

There is no question that climate change is happening; the only arguable point is what part humans are playing in it.

You've got to be fairly solemn [about the environment]. I mean the mere notion that there are three times as many people on Earth as there were when I started making television. How can the Earth accommodate them? When people, including politicians, set their faces against looking at the consequences-it's just unbelievable that anyone could ignore it.

Do we really require so many gardening programmes, makeover programmes or celebrity chefs?

Natural history is not about producing fables.