Many individuals are doing what they can. But real success can only come if there is a change in our societies and in our economics and in our politics.

You'll discover in countries where women have control over their own bodies, where they have education, where they have birth control, where they have facilities and where they are literate, when those things happen, the birth rate falls.

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

What humans do over the next 50 years will determine the fate of all life on the planet.

We really need to kick the carbon habit and stop making our energy from burning things. Climate change is also really important. You can wreck one rainforest then move, drain one area of resources and move onto another, but climate change is global.

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.

The whole of science, and one is tempted to think the whole of the life of any thinking man, is trying to come to terms with the relationship between yourself and the natural world. Why are you here, and how do you fit in, and what's it all about.