The hardest part of returning to a truly healthy environment may be changing the current totally unsustainable heavy-meat-eating culture of increasing numbers of people around the world. But we must try. We must make a start, one by one.

Here we are, the most clever species ever to have lived. So how is it we can destroy the only planet we have?

So long as we continued to attach more importance to our own narrow group membership than to the 'global village' we would propagate prejudice and ignorance. There was absolutely no harm in being part of a small group - indeed, with our hunter-gatherer band mentality it gave comfort, provided us with an inner circle of friends who could be utterly trusted, who were absolutely reliable. It helped give us peace of mind. The danger came only from drawing that sharp line, digging that ditch, laying that minefield, between our own group and any other group that thought differently.

Children can change the world.

When you meet chimps you meet individual personalities. When a baby chimp looks at you it's just like a human baby. We have a responsibility to them.

Each one of us matters, has a role to play, and makes a difference. Each one of us must take responsibility for our own lives, and above all, show respect and love for living things around us, especially each other.

I believe that the tragedy [like terror attack] that's caused so much grief and suffering to so many thousands and thousands of people has also served as a call to action, because many people now are re-examining their own value systems, and the churches, temples, mosques and cathedrals are packed to overflowing for the first time in years.