Narrowing the Definition of Endangered Species: Implications of the U.S. Government's Interpretation of the Phrase “A Significant Portion of its Range” Under the Endangered Species Act of 1973

Abstract

In 2007, the Solicitor for the Department of Interior advocated for an interpretation of the phrase, “a significant portion of its range,” that would effectively narrow the definition of endangered species under the Endangered Species Act. We review the controversy concerning the government's interpretation of the “significant portion of its range” phrase, focusing on recent case law, the Solicitor's Memorandum, and relevant listing actions. We concentrate our discussion on two key conclusions reached by the Solicitor: (a) the term “range” in the phrase refers only to a species' current range, not its historical range and (b) the government is entitled to adapt its definition of the term “significant” on a case by case basis. We find that implementation of the Solicitor's interpretation could significantly reduce the number of species that qualify for protections and ultimately, result in a diminished capacity to provide for the conservation of threatened and endangered species.