The only way to save a rhinoceros is to save the environment in which it lives, because there's a mutual dependency between it and millions of other species of both animals and plants.

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

I suppose happiness is something one enjoys, but I suspect that happiness is not a state but rather a transition.

Terrorism is an immediate problem that people are very concerned about, and I am as concerned about that as anyone else. But it isn't an either or situation.

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.

The fundamental issue is the moral issue.

I don't think whole populations are villainous, but Americans are just extraordinarily unaware of all kinds of things. If you live in the middle of that vast continent, with apparently everything your heart could wish for just because you were born there, then why worry? [...] If people lose knowledge, sympathy and understanding of the natural world, they're going to mistreat it and will not ask their politicians to care for it.