1973: Endangered Species Act (ESA)

Congress passed the Endangered Species Act in 1973. The ESA defined an “endangered species” as any species “in danger of extinction throughout all or a significant portion of its range.”A “threatened” species is one likely to become endangered.”

The ESA provided for the listing and protection of species in imminent danger of extinction.The listing of a species can lead to limitations on activities that affect that species, and in the Act carries penalties for the “taking” of individuals of a listed species."Taking" is broadly defined as "harassing, harming, pursuing, hunting, shooting, wounding, killing, trapping, capturing, or collecting, or attempting to engage in any such conduct.”

The listing process was to be based on scientific considerations only with no mechanism for weighing potential conflicts between protection measures and economic development.Although economic factors are not to be considered in the listing of a species as endangered or threatened, economic impacts, and any other relevant impact, may later be considered by the Secretary of the Interior, along with the best scientific data available, in the designation of critical habitats.

Under the ESA, certain populations of vertebrates can be listed separately. Biologists agreed (in 1990) that there were five separate populations of northern spotted owl living in different parts of the Pacific Northwest. It is possible that only one or two populations could be listed as threatened or endangered.


USDA Forest Service.“Spotted Owl Background Information.” USDA Forest Service, Public Affairs Office; June 15, 1990.