I often get letters, quite frequently, from people who say how they like the programmes a lot, but I never give credit to the almighty power that created nature.

Climate change will affect the whole of humanity, while terrorist attacks will only affect a small section of humanity. Of course, you wouldn't say that if you were related to someone who had been beheaded or blown up or murdered. But 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.

How could I look my grandchildren in the eye and say I knew what was happening to the world and did nothing.

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.

I'm luckier than my grandfather, who didn't move more than five miles from the village in which he was born.

The truth is: the natural world is changing. And we are totally dependent on that world. It provides our food, water and air. It is the most precious thing we have and we need to defend it.

All life is related. And it enables us to construct with confidence the complex tree that represents the history of life