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The Endangered Species Act of 1973

The Endangered Species Act of 1973 (ESA; 16 U.S.C. §§ 1531–1544) was enacted to provide a program for the conservation of endangered and threatened species and the ecosystems upon which they depend.

Last reviewed: 2026-10-16

1. Statutory Classifications

Under 16 U.S.C. § 1532, the statute establishes two conservation categories for declining taxa:

Endangered Status (16 U.S.C. § 1532(6))

Defined as any species in danger of extinction throughout all or a significant portion of its range (other than certain designated pest insect species). Endangered species receive statutory prohibitions against take, import, export, possession, and commercial sale.

Threatened Status (16 U.S.C. § 1532(20))

Defined as any species likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.

Official Source: 16 U.S.C. § 1532 Definitions on uscode.house.gov ↗

2. Section 4(d) Special Rules

Under Section 4(d) of the Act (16 U.S.C. § 1533(d)), whenever a species is listed as threatened, the administrative agency must issue regulations deemed "necessary and advisable to provide for the conservation of such species." Section 4(d) rules allow federal regulators to tailor specific prohibitions and exemptions appropriate to the species' conservation needs.

Official Source: 16 U.S.C. § 1533 Determination of Species Status on uscode.house.gov ↗

3. Listing Petitions & Critical Habitat

Federal listings follow administrative procedures specified in 16 U.S.C. § 1533(b):

  • 90-Day Findings: In response to citizen petitions, the governing agency issues a finding on whether the petition presents substantial scientific information indicating that listing may be warranted.
  • 12-Month Findings: Following status review, the agency issues a formal finding determining whether listing is warranted, not warranted, or warranted but precluded.
  • Critical Habitat (16 U.S.C. § 1533(a)(3)): Concurrently with listing, regulators designate specific geographic areas containing physical or biological features essential to species conservation.

Official Source: 16 U.S.C. § 1533 Rulemaking Procedures on uscode.house.gov ↗

4. Shared Administration

Jurisdiction under the ESA is divided between two federal agencies (50 C.F.R. § 402.01):

  • U.S. Fish and Wildlife Service (Department of the Interior): Manages terrestrial, avian, and freshwater species.
  • NOAA Fisheries / NMFS (Department of Commerce): Manages marine and anadromous species, including whales, seals, sea turtles in marine environments, and marine fish.

Official Sources: USFWS Endangered Species Program on fws.gov ↗ • NOAA Fisheries Endangered Species on fisheries.noaa.gov ↗