I'm no longer sceptical. I no longer have any doubt at all. I think climate change is the major challenge facing the world.

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.

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?

One in eight plant species face extinction.

I'm a humanist. I'm neither one side nor the other.

I just wish the world was twice as big and half of it was still unexplored.

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