This week, University of Chicago faculty members Richard A. Posner and Gary S. Becker discuss and debate the relationship between DDT and the fight against malaria on their blog.

As a self-proclaimed “strong environmentalist” who supports “the ban on using DDT as a herbicide,” Posner writes first about the contemporary decline in genetic diversity due in large part to the rate of species extinction. (Posner has issued a correction: “Unforgivably, I referred to DDT as a ‘herbicide.’ It is, of course, a pesticide. A herbicide is used to destroy weeds and other plants.” Presumably enough DDT would kill plants, and also presumably Posner would oppose such a use. But even so, Posner’s clarification is duly noted.)

“The decline in genetic diversity–to which spraying crops with DDT would be contributing significantly if it were permitted–is alarming even from a purely selfish anthropocentric perspective,” says Posner, “Because such diversity, like other forms of diversification, performs an important insurance function.”

Even so, Posner notes, “The quantities of DDT used in spraying indoor houses in Subsaharan Africa (where 90 percent of malaria deaths occur) are so minute that the environmental effects are inconsequential.” Despite the ban on DDT as an herbicide, an exception allows its use in the fight against malaria. “The puzzle is why the exception is so rarely invoked,” says Posner, because the use of malaria in residual indoor spraying is so cost-effective pared to many other tools in the fight against malaria.

Comparing the threat of AIDS versus that of malaria, Posner concludes, “Considering how much cheaper and easier it would be to (largely) eliminate malaria than to eliminate AIDS (which would require behavioral changes to which there is strong cultural resistance in Africa), the failure of the African countries, the World Health Organization, the World Bank, and private foundations and other nongovernmental organizations to eliminate most malaria by means of indoor spraying with DDT is a remarkable political failure.”

I might also observe that at one point ments, “Not that eliminating childhood deaths from malaria (I have seen an estimate that 80 percent of malaria deaths are of children) would be pletely unalloyed boon for Africa, which suffers from overpopulation.” menter rightly takes Posner to task for this statement, saying, “Economic analysis of social problems can be useful and pelling. The foregoing, however, seems a bit cold-blooded even for an economist. I suspect and hope Posner doesn’t really mean it.”

Gary Becker provides an excellent narrative of the relationship between DDT and malaria in his post. He also points out, “One unintended consequence of the DDT ban was a eback by malaria and some other diseases after they had been in retreat. Other pesticides that replaced DDT have been much less effective at reducing malaria and other diseases transmitted by insects.”

“I am an ‘environmentalist’,” says Becker, “But I do not believe that all reasonable cost-benefit analysis should be suspended when discussing environmental issues. The ban on using DDT in houses to fight malaria is an example of environmentalism that lost all sense of proportion.”

For more on the campaign to bring back DDT to the malaria-fighting arsenal, check out Acton’s Impact ad project.