I suspect that happiness is not a state but rather a transition.

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

Being in touch with the natural world is crucial.

If my grandchildren were to look at me and say, 'You were aware species were disappearing and you did nothing, you said nothing', that I think is culpable. I don't know how much more they expect me to be doing, I'd better ask them.

The human population can no longer be allowed to grow in the same old uncontrollable way. If we do not take charge of our population size, then nature will do it for us and it is the poor people of the world who will suffer most

The notion of ever more old people needing ever more young people, who will in turn grow old and need even more young people, and so on ad infinitum, is an obvious ecological Ponzi scheme.

Steve Irwin did wonderful conservation work but I was uncomfortable about some of his stunts. Even if animals aren't aware that you are not treating them with respect, the viewers are.