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. 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.

People must feel that the natural world is important and valuable and beautiful and wonderful and an amazement and a pleasure.

Humanity is facing a very big, slow, long, drawn-out threat, and that is to do with the way the weather is changing and the size of the population.

I would love to go and see the Himalayan Mountain Kingdoms. There are very few left now. I would loved to have gone to Tibet and Nepal. And there are still parts of central Asia that are utterly unexplored.

Very few species have survived unchanged. There's one called lingula, which is a little shellfish, a little brachiopod about the size of my fingernail, that has survived for 500 million years, but it's survived by being unobtrusive and doing nothing, and you can't accuse human beings of that.

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.

I suffer much less than many of my colleagues. I am perfectly able to go to Australia and film within three hours of arrival.