Humanity is a biological species, living in a biological environment, because like all species, we are exquisitely adapted in everything: from our behavior, to our genetics, to our physiology, to that particular environment in which we live. The earth is our home. Unless we preserve the rest of life, as a sacred duty, we will be endangering ourselves by destroying the home in which we evolved, and on which we completely depend.

If everyone agreed to become vegetarian, leaving little or nothing for livestock, the present 1.4 billion hectares of arable land (3.5 billion acres) would support about 10 billion people.

We don't know nearly enough about the complexities of Nature. If we think we can eliminate natural ecosystems and substitute prosthetic devices, i.e. clean air or water with fusion energy - we are kidding ourselves.

That's the way to get young people. Once they see there are wonderful things to hunt for, to rediscover a species that was thought to be extinct or is extremely rare, to be the first to see a nest, to discover a new species unsuspected close to your home - these are things, I think, with a little education and excitement and the right kind of natural history would actually start a movement that makes going back to nature a profitable adventure.

In science, obsessiveness under psychological control can be a virtue.

Secular humanists can sit around and talk about their love of humanity, but it doesn't stack up against a two-millennium-old funeral high mass.

The cutting of primeval forest and other disasters, fueled by the demands of growing human populations, are the overriding threat to biological diversity everywhere.