I don't think scientists can dictate from above what we should do, because it's not a matter of scientific decision. If you want to have everybody living like a Beverly Hills millionaire, then 2 billion people might be too many. If we want to have a battery-chicken kind of world, with everybody having an absolute minimum diet, you might be able to support 10 billion.

Anyone who opposes methods to control the birth rate, is automatically voting in favour having the death rate go up.

There's no question at all that the population explosion will come to an end. The two basic choices are it'll come to an end because we control our reproduction, and in many areas we have started to do so, or we'll end up with a high death rate. You have to take a personal moral stand on this.

I see harm reduction as a way of engaging people as part of that path to recovery.

Organisms are starting to move in response to climate change all over the place. Bees are disappearing and we don't have many of the native pollinators left to replace them. We're in deep trouble; there's no question about it. But ecologists tend to think of something that's going to be bad in ten years as very fast, and of course, politicians only think of things in a two-, four-, six-year cycle.

In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.

The drilling idea is spherically senseless - it's senseless from whatever point of view you look at it. It'd take 10 years to bring any oil online, and it would probably go to Japan. It sure wouldn't help gasoline prices here. All the economists say gasoline is still too cheap in the United States anyway. So here we're having this huge debate over offshore drilling that is just straightforward nonsense, which won't surprise you.