The Endangered Species Act and “Sound Science”

Eugene H. Buck
Specialist in Natural Resources Policy

M. Lynne Corn
Specialist in Natural Resources Policy

Kristina Alexander
Legislative Attorney

The adequacy of the science supporting implementation of the Endangered Species Act (ESA) is receiving increased congressional attention. While some critics accuse agencies responsible for implementing the ESA of using “junk science,” others counter that decisions that should rest on science are instead being dictated by political concerns.

Under the ESA, certain species of plants and animals (both vertebrate and invertebrate) are listed as either endangered or threatened according to assessments of the risk of their extinction. Once a species is listed, powerful legal tools are available to protect the species and its habitat. Efforts to list, protect, and recover threatened or endangered species under the ESA can be controversial. Some of this controversy stems from the substantive provisions of this law, which can affect the use of both federal and nonfederal lands. The scientific underpinnings of decisions under the ESA are especially important, given their importance for species and their possible impacts on land use and development.

The Fish and Wildlife Service in the Department of the Interior and the National Marine Fisheries Service in the Department of Commerce administer the ESA, and each agency has policies and requirements to ensure the integrity and objectivity of the science that underlies ESA decisions. The Information Quality Act (IQA or Data Quality Act) also imposes general requirements and has resulted in agency changes to carry out the goals of that act to maximize the quality, objectivity, utility, and integrity of information disseminated by the agencies.

In several situations, economic and social disputes have resulted from actions taken to list, protect, and recover species under the ESA. Critics in some of these disputes assert that the science supporting ESA actions is insufficiently rigorous. Others assert that in some instances decisions were political rather than scientific. Controversy has arisen over what might be the essential elements of “sound science” in the ESA process and whether the ESA might benefit from clarification of how science is to be used in its implementation. The courts have had occasion to review the use of science by the agencies, which generally must show their decisions were not arbitrary and rest on credible science. For some purposes, if that science is the best available, even if it is considered imperfect or incomplete, it still may be used.

Several bills affecting science as used in the ESA have been introduced in recent Congresses, but to date none have been enacted. Legislative activity in the 111th Congress is summarized in CRS Report R40185, The Endangered Species Act (ESA) in the 111th Congress: Conflicting Values and Difficult Choices, by Eugene H. Buck et al.

This report provides a context for evaluating legislative proposals through examples of how science has been used in selected cases, a discussion of the nature and role of science in general, and its role in the ESA process in particular, together with general and agency information quality requirements and policies, and a review of how the courts have viewed agency use of science.


Date of Report: October 26, 2011
Number of Pages: 30
Order Number: RL32992
Price: $29.95

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