Uncertainty And The Endangered Species Act

The U.S. Endangered Species Act requires the U.S. Fish and Wildlife Service to use the "best available" information when deciding whether to list species as threatened or endangered, and when regulating conservation for species already listed. The agency has discretion to determine the types, quantity, and quality of the information it uses as "best available," but little discretion to defer decision making in cases where important scientific information is lacking. Complexities of nature, obscurity of many species' life history, and changing environmental circumstances are only some of the reasons why information is rarely complete, and why decisions are almost always made in the face of uncertainties. These uncertainties could lead to decision errors and the consequences might be failure to prevent extinction or imposition of unnecessary regulatory requirements. Furthermore, real or perceived errors could lead to legal action and loss of the agency's credibility. This Paper discusses some recent examples of how the Fish and Wildlife Service has dealt explicitly with uncertainty in its administration of the Endangered Species Act.