A few brief responses (Becker and I are planning to discuss population issues further next week) to a characteristically interesting set of comments.
The most frequent comment is that I am worrying too much about population growth because the vast population growth that the world has experienced in past centuries has not resulted in a net diminution of human welfare. But we do not live in history; we live in the present and the future. To suppose that an established trend is bound to continue is to be guilty of na√Øve extrapolation. I do wish to emphasize, however, in light of one of the comments, that I have never suggested and do not believe that the world is going to run out of food any more than it is going to run out of energy sources.
Refusal to recognize developments that may make the future differ from the past is illustrated by a comment which states that only the United States has the technology necessary to create devastatingly effective bioweaponry. That is a dangerous error. Several years ago, Australian plant scientists, by injecting mousepox virus with commercially available genetic material, increased the lethality of the virus and at the same time made it immune to the mousepox vaccine. Mousepox is biologically similar to smallpox. Those same scientists could if they wanted to, and if they could get hold of smallpox virus, make the virus immune to existing vaccines and even more lethal than it is in nature, where the death rate is 30 percent. Because smallpox is highly contagious even before symptoms appear, and its initial symptoms are ambiguous, hundreds of millions of people could be infected before the epidemic was even discovered, and there would no vaccinated health workers or security personnel to enforce a quarantine. Although all smallpox virus is supposed to be under lock and key in two laboratories, one in the United States and one in Russia, this is not certain and in any event it is expected that the smallpox virus will be synthesized within five years; the polio virus has already been synthesized.
That is our future.
One comment accuses me of putting environmental welfare ahead of human welfare and even of "deifying" the environment. That is not a correct characterization of my view. I am not a Green. Environmental and human welfare are interrelated; otherwise there would be no antipollution policies. Global warming is a profound danger to human welfare. Granted, there is still some scientific debate over global warming, but increasingly it resembles the scientific debate over the health consequences of cigarette smoking. There is never complete certainty in scientific matters, but the efforts of a minority of scientists to debunk global warming are beginning to resemble the efforts of a minority of scientists to debunk evolution.
For further discussion of the matters touched on in this response, see my book Catastrophe: Risk and Response (Oxford University Press, 2004).