Endangered Species Act: An Overview

Background

The Endangered Species Act (ESA) was enacted by Congress in 1973 to provide federal protection to species of wildlife that are in danger of becoming extinct. At its core, the ESA establishes protections for wildlife, fish, and plants that are identified as either “threatened” or “endangered.” Those protections include a prohibition on “take” of a species, the requirement that all federal agencies ensure that their actions will not jeopardize the continued existence of threatened or endangered species, and the drafting and implementation of recovery plans for at risk species. The ESA is recognized as one of the strongest wildlife protection statutes in the world.

Although the ESA is considered one of the most powerful pieces of legislation dedicated to conserving wildlife, it is not the first piece of legislation with that purpose. In 1966, Congress passed the Endangered Species Preservation Act, which authorized the Secretary of the Interior to compile a list of endangered species and provided the Fish & Wildlife Service (FWS) with $15 million per year to buy habitat for listed species. In 1969, Congress passed the Endangered Species Conservation Act, which allowed the Secretary of Interior to list foreign species and prohibited the importation of products made from those species. The ESA ultimately replaced the 1969 Act, providing endangered species with more protection than any prior legislation.

The ESA is administered by two agencies: the U.S. Fish & Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) (collectively “the Services”). FWS administers the ESA for terrestrial and freshwater species, while NMFS administers the ESA for marine species. These agencies are commonly referred to as the “listing agencies.”

Federal Regulatory Authority

Under the ESA, Congress has delegated authority to administrative agencies, such as USDA FDA, EPA, and the Services, to create regulations implementing the statute. In 2024, the Supreme Court of the United States issued two rulings that have begun to reshape how judges decide cases challenging those regulations and that agency authority.

Loper Bright Enters. v. Raimondo, 144 S. Ct. 2244 (2024) overruled the long-standing doctrine of deference established in Chevron, U.S.A., Inc. v. Nat. Res. Def. Council, Inc., 467 U.S. 837 (1984). Chevron deference was a two-step process that clarified how and when federal courts should defer to an agency regulation interpreting a statute.  Chevron only applied in situations where a court had determined that the statutory language the agency was interpreting was ambiguous.  If it was ambiguous, the court would consider whether the agency’s interpretation of the statutory language was “reasonable”.  If it was reasonable, the court was required to defer to the agency’s interpretation. If it was not, the court would overrule the interpretation.

Loper Bright formally overturned Chevron. In a 6-3 decision, the Supreme Court held that “courts may not defer to an agency interpretation of the law simply because a statute is ambiguous[.]” Following the ruling, courts are instead required to exercise independent judgment in determining whether an administrative agency has acted within its statutory authority.  Courts may still seek guidance from the agencies involved, but courts are no longer required to defer to an agency’s interpretation of a statute.

In Corner Post, Inc. v. Bd. of Governors of the Fed. Rsrv. Sys., 144 S. Ct. 2440 (2024), the Supreme Court extended the period of time during which a party may file a lawsuit challenging federal agency actions. According to 28 U.S.C.S. § 2401(a), the six-year statute of limitations began to run when an administrative agency’s action was “final.”  In Corner Post, the Supreme Court ruled that an action becomes “final” when a plaintiff suffers an injury, rather than when a “final regulation” is released. This ruling expands the potential for plaintiffs to challenge federal agency rules and regulations that have been final for over six years.

These rulings have fundamentally changed how courts will resolve lawsuits challenging agency regulations for misinterpreting the agency’s statutory authority. The impacts have been most prevalent in areas of the law that are dominated by statutes with relatively ambiguous language, such as the ESA, where Congress has relied on agency regulations to fill in gaps. These developments are significant for the agricultural industry.

“Threatened” vs. “Endangered” Species

An important feature of the ESA is its distinction between endangered and threatened species. The ESA defines an endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range.” The ESA defines a threatened species as “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” The “foreseeable future” extends only as far as the Services can make reasonably reliable predictions about future threats to a species and the species’ responses to those threats. If a species is listed as endangered under the ESA, that species is automatically provided the full protection of the Act. However, if a species is listed as threatened, then the listing agency has the authority to determine which protections should apply to the species.

While listing a species as endangered provides the species with greater protection, listing a species as threatened provides two major benefits: first, it provides the species with federal protection before the species reaches the point of near-extinction; second, if a species was initially listed as endangered, the threatened status allows the scaling back of ESA protection as the species recovers and is no longer in need of maximum protections.

Take and Take Permits

Perhaps one of the most well-known components of the ESA is the Section 9 prohibition against take of a species. Under the ESA, the term “take” is broadly defined as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” The term “harm” is further defined by regulation as “an act which actually kills or injures wildlife. Such an act may include significant habitat modification or degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding, or sheltering.”

When a species is listed as endangered under the ESA, any take of that species is expressly prohibited without a take permit. Take permits may be obtained by both public and private parties. An incidental take permit authorizes the taking of a listed species when the take is incidental to an otherwise lawful activity. These permits are usually very precise, detailing exactly which species is authorized for incidental take and how many individual members of that species will be covered by the permit. An incidental take permit will only be issued after completion of a Habitat Conservation Plan.

Habitat Conservation Plans

Habitat Conservation Plans (HCP) are planning documents required under the ESA as part of an application for an incidental take permit. HCPs describe the anticipated effects of the proposed take, the measures that will be used to minimize or mitigate the impacts of the proposed take, and how the HCP will be funded. HCPs are primarily used by private and non-federal parties carrying out otherwise legal activities that are likely to result in the take of a listed species.

Listing and Delisting

When making a listing decision, the Services must rely on the best available scientific and commercial information. When evaluating a species for listing, the listing Secretary may consider many factors, including: (1) damage to or destruction of the species’ habitat; (2) overutilization of the species for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) inadequacy of existing protection; and (5) other natural or manmade factors that affect the continuation of the species. Importantly, the Services do not need to base their listing decisions on all five factors being present. A finding under any one of these factors may be sufficient to support a listing. Ultimately, the question of whether a species should be listed as threatened or endangered depends on the severity of its population decline and the threats to its continued survival.

Species may be listed on the initiative of the Services, but more commonly a species will be listed by a petition from an individual, group, or state agency. The ESA requires that “to the maximum extent possible,” the Services must make an initial determination on a species’ status within 90 days of receiving a listing petition. The 90-day determination period allows the agency to assess whether the petition provides sufficient information to support a finding that the petitioned action may be warranted. If the agency determines that the petition presents sufficient information, then the agency has 12 months to conduct a status review of the species. There are three possible outcomes of a status review: (1) the agency finds that the petitioned action is not warranted; (2) the agency finds that the petitioned action is warranted, and a listing proposal will soon be published in the Federal Register; or (3) the agency finds that the petitioned action is warranted, but the action will not take place because it is precluded by a species with a higher listing priority. As of May 2026, there are 2,386 species listed under the ESA, with 1,680 of those species located within the United States. Out of those 1,682 species located within the United States, 1,409 are listed with active Recovery Plans. Those 1,682 species are composed of  742 animal species and 938 plant species.

“Delisting” is the term used when a species is removed from the list of threatened and endangered species. A species will be delisted if the Services determine that the species is either extinct, no longer meets the definition of a threatened or endangered species, or no longer qualifies as a “species” under the ESA. The decision to delist a species must be made solely upon the basis of the best available scientific and commercial information, with the decision-maker considering several factors including population size, stability of habitat quality and quantity, and control or elimination of threats. A species will typically be delisted when it has made a sufficient recovery, when new populations of the species are discovered indicating the species is no longer in danger of becoming extinct, or if the species has suffered extinction. As of May 2026, only 138 species have ever been delisted.

Critical Habitat

When a species is listed under the ESA, the listing agency may also designate critical habitat. Critical habitat is the geographic area that contains the physical or biological features essential to the conservation of the species that the area is designated for. Designation of critical habitat, like all listing decisions, must be made based on the best available scientific and commercial data. Critical habitat can be occupied by the species at the time of designation, but that is not a requirement. Unoccupied areas may be designated as critical habitat so long as they contain the physical or biological features necessary for the conservation of the species. Unlike listing determinations, agencies have always been permitted to take economic factors into account when making critical habitat determinations.

In a 2018 decision titled Weyerhaeuser Co. v. U.S. Fish and Wildlife Serv., 586 U.S. 9 (2018), the Supreme Court concluded that in order to meet the definition of critical habitat, an area must be habitat. More specifically, the Supreme Court ruled that if an area is designated as critical habitat for that species, it must be capable of serving as habitat for that species.

Any area, whether federally or privately owned, may be designated as critical habitat. However, a critical habitat designation will only affect private land if some federal action is also involved. The ESA instructs all federal agencies to avoid destruction or adverse modification of critical habitat, either through direct action or through projects that they fund. This same prohibition is not placed upon private landowners who are only required to ensure that they do not take a listed species.

Cooperation with Federal Agencies

Section 7 of the ESA requires federal agencies to promote the Act’s conservation purposes by consulting with the Services to ensure that any federally authorized, funded, or direct action is not likely to jeopardize the continued survival of any listed species or adversely modify any critical habitat.

Requests for formal consultation must include descriptions of the proposed action, effects of the action, efforts to offset effects of the action, and several other factors relating the action to the impacted species. The formal consultation process results in a document known as a Biological Opinion (BiOp) which details the effect the proposed federal project would have on any listed species within the project area. Regulations released in August 2019 state that, when preparing a BiOp, the Services can consider proposed activities that will offset the effects of the action. If FWS or NMFS concludes in a BiOp that a proposed project is likely to place a listed species in “jeopardy,” then the consulting agency will offer “reasonable and prudent alternatives” about how the proposed project could be modified to avoid causing harm.

Recovery Plans

In addition to designating critical habitat, FWS and NMFS are tasked with developing recovery plans for every listed species. Recovery plans outline the steps needed to return a species to ecological health. The plans include when and where the steps will need to take place, along with the estimated cost of recovery and a general timeline. However, neither the ESA nor its regulations provide a large amount of detail on requirements for the recovery plans, and the plans are not binding on federal agencies.

Safe Harbor Agreements

Safe Harbor Agreements (SHA) are voluntary agreements between the federal government and non-federal landowners. These agreements are available only on private lands. Under an SHA, the landowner agrees to undertake actions that contribute to the conservation and recovery of listed species. In exchange, the landowner will not be bound by any land use restrictions not included in the SHA, even if the conservation activity leads to an increase in the population of listed species present on the landowner’s property. The SHA will also authorize any incidental take of a listed species resulting from the conservation activities carried out by the landowner. Additionally, the Services cannot require any new or additional land management activities by SHA participants without their consent.

SHAs must be initiated by the private landowner and can take anywhere from six to nine months to develop. After an SHA expires, the landowner may choose to either renew the agreement or let the agreement lapse. If the agreement lapses, the landowner is free to return the property to the baseline conditions that existed before the SHA was in place.