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

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

Bringing nature into the classroom can kindle a fascination and passion for the diversity of life on earth and can motivate a sense of responsibility to safeguard it.

Birds were flying from continent to continent long before we were. They reached the coldest place on Earth, Antarctica, long before we did. They can survive in the hottest of deserts. Some can remain on the wing for years at a time. They can girdle the globe. Now, we have taken over the earth and the sea and the sky, but with skill and care and knowledge, we can ensure that there is still a place on Earth for birds in all their beauty and variety - if we want to... And surely, we should.

There are some four million different kinds of animals and plants in the world. Four million different solutions to the problems of staying alive.

They always mean beautiful things like hummingbirds. I always reply by saying that I think of a little child in east Africa with a worm burrowing through his eyeball. The worm cannot live in any other way, except by burrowing through eyeballs. I find that hard to reconcile with the notion of a divine and benevolent creator.

If I can make programmes when I'm 95, that would be fine. But I would think I'll have had enough by then.