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

All our environmental problems become easier to solve with fewer people and harder - and ultimately impossible to solve - with ever more people.

Sentimentalising is anathema, as far as I am concerned. It leads you into ethical problems about violence and killing and eating meat. The whole world becomes topsy-survy if you impose moralities that were evolved within human society on what a blowfly or what a parasite does... there are lots of emotions you can deduce from an animal's behaviour that are correct, but when you start saying it's feeling guilty or thinking or a loved one or mourning, you must be very careful of those feelings.

The World is full of wonders, but they become more Wonderful, not less Wonderful when Science looks at them.

The reverse side of the coin in having this extraordinary ability to go anywhere, is that no one anywhere is remote any more.

What I am interested in with birds, just as I am with spiders or monkeys, is what they do and why they do it.

I can mention many moments that were unforgettable and revelatory. But the most single revelatory three minutes was the first time I put on scuba gear and dived on a coral reef. It's just the unbelievable fact that you can move in three dimensions.