As Gary Comstock, the eminent bioethicist and philosopher, so perceptively notes ("Make plans on the hoof", Research, THES, December 22), the precautionary principle can lead to diametrically opposite conclusions on policy issues such as global warming or genetically modified crops.
The precautionary principle is the environmentalists' version of the Hippocratic Oath, that is, "do no harm". It has been used to justify banning GM crops, controlling greenhouse gases and eliminating DDT. But the justifications do not account for any risks that those policies might generate.
This is probably because following the precautionary principle provides no guidance on how to evaluate a policy if it results simultaneously in uncertain benefits and harm.
Such one-sided accounting results in a cure that is worse than the disease. To guard against such perverse outcomes, I have developed a framework to evaluate policies where the net result could be ambiguous. The framework attempts to sort competing claims on both sides of the ledger by considering the nature, magnitude and certainty of the positive and negative effects of a ban, and the likelihood that a ban would reduce or aggravate the effects.
I have applied this framework to evaluate policies on GM crops, global warming and DDT. The results - available in policy studies published by the Center for the Study of American Business, Washington University, Missouri, and the Save Children from Malaria Campaign - tend to vindicate Comstock's iconoclasm.
I conclude that there ought not to be a blanket ban on research, development and commercialisation of GM crops because, despite some hypothetical benefits, it would do more harm to public health (partly because it would make it harder to reduce hunger and malnutrition and so reduce mortality and extend life expectancy) and to the environment (because it would increase the amount of land and water devoted to agriculture, further intensifying the threat to global biodiversity).
Indur M. Goklany
Manager, Science and Engineering
Office of Policy Analysis
United States Department of the Interior
Views expressed here are personal to the author.