The precautionary principle, which has become a general principle of international law, says that if the environmental consequences of human action may be serious and irreversible, efforts should be made to avoid or lessen them. It is based on the classical virtue of “prudence” and embraces the folk wisdom of “better safe than sorry” and “look before you leap.”

Although uncertainties about the consequences of human behavior have always existed, they have become more significant in recent times because of the growing scope, complexity, and hazard of human activities. This means it is becoming more vital to be able to prevent the harm these activities might do, even without being sure what that is.

Environmental regulations generally aim to prevent known risks rather than anticipate and prevent ...