My first policy move would be to try to get a conversation going in the US about what people stand for and what we really want. Do we want to keep adding people to the world and to our country until we move to a battery-chicken kind of existence and then collapse? Or do we want to think hard about what really is valuable to us, and figure out how many people we can supply that to sustainably?

Your children should have it impressed upon them that their adult life-style will bear very little resemblance to yours and that they should now be acquiring knowledge, skills, values, and tastes that will sustain them in less materially affluent circumstances. On the other hand, the fresh insights and imaginations of your children may help you find a viable future while there's still time.

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.

Most of the scientists I know think civilization is teetering on the brink of a global disaster. They just don't know when it's going to hit. I don't have the answer to that either. I'm scared as hell.

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

We're one of the most highly regulated industries, and we have to pay attention to what government is doing.

We ought to take good care of everybody we have on the planet, but we ought to regulate the rate at which people join us. The old saying is, "It's the top of the ninth inning, and humanity has been hitting nature hard, but you've always got to remember that nature bats last."