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.

I don't like rats, but there's not much else I don't like. The problem with rats is they have no fear of human beings, they're loaded with foul diseases, they would run the place given half the chance, and I've had them leap out of a lavatory while I've been sitting on it.

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 coordinated view about the planet it’s going to get worse and worse.

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 we're lucky to be living when we are, because things are going to get worse.

The nature of human beings is that they'd far rather face the disaster that is happening tonight than the one that is happening tomorrow.

Nothing in the natural world makes sense - except when seen in the light of evolution