The Endangered Species Act

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Chapter 2
The Endangered Species Act

The Endangered Species Act of 1973 (ESA) is generally considered one of the most far-reaching laws ever enacted by any nation for the preservation of wildlife. The passage of the ESA resulted from alarm at the decline of numerous species worldwide, as well as from recognition of the importance of preserving species diversity. The purpose of the ESA is to identify species that are either endangered—at risk of extinction throughout all or a significant portion of their range—or threatened—likely to become endangered in the foreseeable future. With the exception of recognized insect pests, all animals and plants are eligible for listing under the ESA. Listed species are protected without regard to either commercial or sport value.

For its supporters, the Endangered Species Act has proved to be one of the most effective conservation laws ever enacted. Many Americans believe that the ESA has saved numerous species from extinction. However, critics charge that the ESA puts too many restrictions on land and water development projects and is too expensive for the results that it achieves.


Conservation has a long history. One of the oldest examples dates from 242 bce, when the Indian emperor Asoka created nature reserves in Asia. Marco Polo reported that the Asian ruler Kublai Khan (1215–94) helped conserve bird and mammal species valued for hunting by banning hunting during their reproductive periods. He also helped to increase their numbers by planting food and providing protected cover areas. In South America, during the reign of the Inca kings, many species of seabirds were protected.

By the mid-nineteenth century many governments had developed an interest in wildlife conservation and an awareness of the need to protect natural habitats. In 1861 painters of the Barbizon school established the first French nature reserve, which covered nearly 3,458 acres of forest at Fontainebleau near Paris. Three years later the American government set aside the Yosemite Valley in California as a National Reserve. This became Yosemite National Park in 1890. Wyoming's Yellowstone Park was created in 1872 and became the first U.S. National Park.

Organizations and laws dedicated to the protection of species soon followed. In 1895 the first international meeting for the protection of birds was held in Paris, and resulted in new laws protecting species in several countries. The first international conference for the protection of nature was held in 1913. The International Whaling Commission was established in 1946, and two years later, the World Conservation Union was founded as the International Union for the Protection of Nature. In 1956 that organization became the International Union for Conservation of Nature and Natural Resources, or IUCN. In 1990 the name became IUCN—The World Conservation Union.

In 1961 a private conservation organization, the World Wildlife Fund (WWF), was founded. The Chinese giant panda was selected as the WWF symbol, not only because of the animal's great popularity, but also to reaffirm the international character of nature conservation, and to emphasize the independence of wildlife conservation from political differences. The Convention on International Trade in Endangered Species (CITES), an international treaty established to regulate commerce in wildlife, was first ratified in 1975 in an attempt to block both the import and export of endangered species and to regulate international trade in threatened species.

In the United States, Congress passed the Endangered Species Preservation Act in 1966, and the first species were listed in 1967. (See Table 2.1.) This established a process for listing species as endangered and provided some measure of protection. The Endangered Species Conservation Act of 1969 provided protection to species facing worldwide extinction, prohibiting their import and sale within the United States.

First list of endangered species, 1967
In accordance with section 1(c) of the Endangered Species Preservation Act of October 15, 1966 (80 Stat. 926; 16 U.S.C. 668aa(c) I [the Secretary of the Interior] find after consulting the states, interested organizations, and individual scientists, that the following listed native fish and wildlife are threatened with extinction.
source: Stewart L. Udall, "Native Fish and Wildlife Endangered Species," in Federal Register, vol. 32, no. 48, March 11, 1967
  • Indiana bat—Myotis sodalis
  • Delmarva Peninsula fox squirrel—Sciurus niger cinereus
  • Timber wolf—Canis lupus lycaon
  • Red wolf—Canis niger
  • San Joaquin kit fox—Vulpes macrotis mutica
  • Grizzly bear—Ursus horribilis
  • Black-footed ferret—Mustela nigripes
  • Florida pantherFelis concolor coryi
  • Caribbean monk seal—Monachus tropicalis
  • Guadalupe fur seal—Arctocephalus philippi townsendi
  • Florida manatee or Florida sea cow—Trichechus manatus latirostris
  • Key deer—Odocoileus virginianus clavium
  • Sonoran pronghorn—Antilocapra americana sonoriensis

  • Hawaiian dark-rumped petrel—Pterodroma phaeopygia sandwichensis
  • Hawaiian goose (nene)—Branta sandvicensis
  • Aleutian Canada gooseBranta canadensis leucopareia
  • Tule white-fronted goose—Anser albifrons gambelli
  • Laysan duck—Anas laysanensis
  • Hawaiian duck (or koloa)—Anas wyvilliana
  • Mexican duck—Anas diazi
  • California condor—Gymnogyps californianus
  • Florida Everglade kite (Florida Snail Kite)—Rostrhamus sociabilis plumbeus
  • Hawaiian hawk (or ii)—Buteo solitarius
  • Southern bald eagleHaliaeetus t. leucocephalus
  • Attwater's greater prairie chicken—Tympanuchus cupido attwateri
  • Masked bobwhite—Colinus virginianus ridgwayi
  • Whooping craneGrus americana
  • Yuma clapper rail—Rallus longirostris yumanensis
  • Hawaiian common gallinule—Gallinula chloropus sandvicensis
  • Eskimo curlew—Numenius borealis
  • Puerto Rican parrot—Amazona vittata
  • American ivory-billed woodpecker—Campephilus p. principalis
  • Hawaiian crow (or alala)—Corvus hawaiiensis
  • Small Kauai thrush (puaiohi)—Phaeornia pulmeri
  • Nihoa millerbird—Acrocephalus kingi
  • Kauai oo (or oo aa)—Moho braccatus
  • Crested honeycreeper (or akohekohe)—Palmeria dolei
  • Akiapolaau—Hemignathus wilsoni
  • Kauai akialoa—Hemignathus procerus
  • Kauai nukupuu—Hemignathus lucidus hanapepe
  • Laysan finchbill (Laysan Finch)—Psittirostra c. cantans
  • Nihoa finchbill (Nihoa Finch)—Psittirostra cantans ultima
  • Ou—Psittirostra psittacea
  • Palila—Psittirostra bailleui
  • Maui parrotbill—Pseudonestor xanthophyrys
  • Bachman's warbler—Vermivora bachmanii
  • Kirtland's warbler—Dendroica kirtlandii
  • Dusky seaside sparrow—Ammospiza nigrescens
  • Cape Sable sparrow—Ammospiza mirabilis

Reptiles and Amphibians
  • American alligator—Alligator mississippiensis
  • Blunt-nosed leopard lizard—Crotaphytus wislizenii silus
  • San Francisco garter snakeThamnophis sirtalis tetrataenia
  • Santa Cruz long-toed salamander—Ambystoma macrodactylum croceum
  • Texas blind salamander—Typhlomolge rathbuni
  • Black toad, Inyo County toad—Bufo exsul

  • Shortnose sturgeon—Acipenser brevirostrum
  • Longjaw Cisco—Coregonus alpenae
  • Paiute cutthroat trout—Salmo clarki seleniris
  • Greenback cuttthroat trout—Salmo clarki stomias
  • Montana Westslope cutthroat trout—Salmo clarki
  • Gila trout—Salmo gilae
  • Arizona (Apache) trout—Salmo sp.
  • Desert dace—Eremichthys acros
  • Humpback chub—Gila cypha
  • Little Colorado spinedace—Lepidomeda vittata
  • Moapa dace—Moapa coriacea
  • Colorado River squawfish—Ptychocheilus lucius
  • Cui-ui—Chasmistes cujus
  • Devils Hole pupfish—Cyprinodon diabolis
  • Commanche Springs pupfish—Cyprinodon elegans
  • Owens River pupfish—Cyprinodon radiosus
  • Pahrump killifish—Empetrichythys latos
  • Big Bend gambusia—Gambusia gaigei
  • Clear Creek gambusia—Gambusia heterochir
  • Gila topminnow—Poeciliopsis occidentalis
  • Maryland darter—Etheostoma sellare
  • Blue pike—Stizostedion vitreum glaucum


Passed by the U.S. Congress in 1973, the Endangered Species Act was substantially amended in 1978, 1982, and 1987. The ESA is administered by the U.S. Department of the Interior through the U.S. Fish and Wildlife Service (FWS). The U.S. Department of Commerce, through the National Marine Fisheries Service (NMFS), is responsible for most marine (ocean-based) species and those that are anadromous (migrate between fresh waters and marine waters). The Biological Resources Division of the U.S. Geological Survey (USGS) conducts research on species for which the Fish and Wildlife Service has management authority.

It should be noted that the original Endangered Species Act defined the word "species" to include species, subspecies, or "smaller taxa." Taxa is the plural of taxon, which is a grouping on the taxonomic table. In 1978 the ESA was amended to define a smaller taxon for vertebrates (animals with a backbone) as a "distinct population segment" (DPS). A DPS is a distinct population of vertebrates capable of interbreeding with each other that live in a specific geographical area. A DPS is usually described using geographical terms, such as northern or southern, or by a given latitude or longitude. In 1991 the National Marine Fisheries Service developed a policy defining the DPS for Pacific salmon populations. Salmon are anadromous, meaning they migrate between the ocean and inland fresh waters. Most salmon migrate in groups at particular times of the year. Each of these groups is called a stock. The NMFS developed a new term, the evolutionarily significant unit (ESU), to refer to a distinct stock of Pacific salmon.

In summary, the word "species" as used in the Endangered Species Act can mean a species, a subspecies, a DPS (vertebrates only), or an ESU (Pacific salmon only).


Under the Endangered Species Act there are five criteria that must be evaluated before a decision is made to list a species:

  • The present or threatened destruction, modification, or curtailment of the species' habitat or range
  • Overutilization for commercial, recreational, scientific, or educational purposes
  • Disease or predation
  • The inadequacy of existing regulatory mechanisms
  • Other natural or manmade factors affecting the species' survival

The primary status codes assigned to listed species are E for endangered and T for threatened. However, there are numerous other status codes for specific types of listings as shown in Table 2.2. Details of these listing actions are provided in the sections below.

In February 2006 there were 997 U.S. species (398 animals and 599 plants) and 520 foreign species (519 animals and one plant) listed as endangered, and 275 U.S. species (129 animals and 146 plants) and forty-six foreign species (forty-four animals and two plants) listed as threatened under the ESA. Thousands of other species are being studied to see if they need to be added to the list. (See Table 1.2 in Chapter 1.)

The Listing Process

The process by which a species becomes listed under the Endangered Species Act is a legal process with specifically defined steps. Successful listing results in regulations that are legally enforceable within all U.S. jurisdictions. At various stages of the listing process the U.S. Fish and Wildlife Service or the National Marine Fisheries Service publishes their actions in the Federal Register, an official document published daily by the National Archives and Records Administration in Washington, D.C. The Federal Register details specific legal actions of the federal government, such as rules, proposed rules, notices from federal agencies, executive orders, and miscellaneous presidential documents. Online access to the Federal Register is available at

There are three ways for the listing process to be initiated:

Endangered Species Act status codes
source: Adapted from "Endangered Species Act Status Codes," in Species List Help File, U.S. Department of the Interior, U.S. Fish and Wildlife Service, Undated, (accessed February 23, 2006)
EmEEmergency listing, endangered
EmTEmergency listing, threatened
EXPE, XEExperimental population, essential
EXPN, XNExperimental population, non-essential
SAE, E(S/A)Similarity of appearance to an endangered taxon
SAT, T(S/A)Similarity of appearance to a threatened taxon
PEProposed endangered
PTProposed threatened
PEXPE, PXEProposed experimental population, essential
PEXPN, PXNProposed experimental population, non-essential
PSAE, PE(S/A)Proposed similarity of appearance to an endangered taxon
PSAT, PT(S/A)Proposed similarity of appearance to a threatened taxon
CCandidate taxon, ready for proposal
D3ADelisted taxon, evidently extinct
D3BDelisted taxon, invalid name in current scientific opinion
D3CDelisted taxon, recovered
DADelisted taxon, amendment of the act
DMDelisted taxon, recovered, being monitored first five years
DODelisted taxon, original commercial data erroneous
DPDelisted taxon, discovered previously unknown additional populations and/or habitat
DRDelisted taxon, taxonomic revision (improved understanding)
ADProposed delisting
AEProposed reclassification to endangered
ATProposed reclassification to threatened
  • Submittal of a petition to the U.S. Fish and Wildlife Service or the National Marine Fisheries Service (hereafter called the "Agencies")
  • Initiative of the Agencies
  • Emergency designation by the Agencies

Figure 2.1 diagrams the most common listing process under the ESA, one that begins with a petition submittal.


The process for listing a new species as endangered or threatened begins with a formal petition from a person, organization, or government agency. This petition is submitted to the U.S. Fish and Wildlife Service for terrestrial and freshwater species or to the National Marine Fisheries Service for marine and anadromous species. All petitions must be backed by published scientific data supporting the need for listing. Within ninety days, the FWS or NMFS determines whether there is "substantial information" to suggest that a species requires listing under the Endangered Species Act.


A status review is triggered when a petition is found to suggest that listing may be necessary or upon the initiative of the U.S. Fish and Wildlife Service or the National Marine Fisheries Service. The purpose of a status review is to determine whether or not a listing is warranted and what that listing should be.

The FWS defines a status review as follows: "the act of reviewing all the available information on a species to determine if it should be provided protection under the ESA. A status review should also use the knowledge of experts; the greater the extent to which Service biologists can build an external consensus using the expertise of various parties (e.g., Federal, State, Tribal, University, Heritage programs), the better." Comments and information are also requested from the general public through publication of a notice in the Federal Register.

The Status Review must be completed within twelve months. There are three possible determinations from the status review:

  • Listing is not warranted
  • Listing is warranted but precluded
  • Listing is warranted


A finding that listing is not warranted must be accompanied by information explaining why the data presented do not support the petitioned action or why there are not enough data to make an appropriate determination.


In some cases it may be decided that a species should be proposed for listing, but development of the listing regulation is precluded by other listing activities with higher priorities. In other words, the Agency acknowledges that a species deserves protection under the ESA, but the Agency has other priorities that it believes must come first. The species is designated a "candidate species."

Candidate species are assigned a listing priority number ranging from 1 to 12 with lower numbers (1-3) indicating greater priority compared to other candidates. Priority is determined based on three considerations:

  • The magnitude of the threats facing the species
  • The immediacy of the threats facing the species
  • The taxonomic uniqueness of the species

The ratings table is shown in Table 2.3. The National Marine Fisheries Service has a different definition for candidate species. That agency calls them "species of concern" and does not propose them for listing on the basis that available information is inadqueate to justify doing so.

Candidate species are re-evaluated annually to confirm that listing continues to be appropriate. These reevaluations continue until the species is proposed for listing or until its status improves sufficiently to remove it from consideration for listing. The Agencies work with state wildlife agencies and other groups to help preserve and improve the status of candidate species, hoping that populations may recover enough that species will not require listing.

In February 2006 there were 282 candidate species designated under the ESA, and distributed as shown in Figure 2.2. Just over half the candidates were plant species.


A determination that listing is warranted means that a species is officially proposed for listing through the publication of this action in the Federal Register. At this point, the Agency asks at least three independent biological experts to verify that the petitioned species requires listing under either threatened or endangered status. After that, input from the public, from other federal and state agencies, and from the scientific community is welcomed. This period of public comment typically

Basis for listing priority for candidate species
source: "Listing Priority Guidance Number," in "Table 1—Candidate Notice of Review (Animals and Plants)," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 17, 2006, (accessed February 22, 2006)
HighImminentMonotypic genus1
Non-imminentMonotypic genus4
Moderate to lowImminentMonotypic genus7
Non-imminentMonotypic genus10

lasts sixty days, but may be extended in some cases. Within forty-five days of proposal issuance, interested parties can request public hearings be held on the issues involved with listing. Such hearings are also held in cases where public interest is high in the listing outcome.

In February 2006 there were fifteen species proposed for listing under the ESA: twelve species of pomace fly, two fish species—cowhead lake tui chub and coho salmon—and a flowering plant called Graham's beardtongue.


After a listing has been proposed the Agency must take one of three possible actions:

  • Withdraw the proposal—the biological information is found not to support listing the species
  • Extend the proposal period—there is substantial disagreement within the scientific community regarding the listing. Only one six-month extension is allowed, and then a final decision must be made.
Delisted U.S. and foreign species, March 2006
Inverted common nameScientific nameListing statusa
Note: Entire range unless otherwise noted.
aListing status:
    D3A      Delisted taxon, evidently extinct
    DA      Delisted taxon, amendment of the act
    DM      Delisted taxon, recovered, being monitored first five years
    DO      Delisted taxon, original commercial data erroneous
    DP      Delisted taxon, discovered previously unknown additional populations and/or habitat
    DR      Delisted taxon, taxonomic revision (improved understanding)
    SAT      Similarity of appearance to a threatened taxon
bDistinct population segment.
source: "Delisted Species Report as of 3/9/2006," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, March 9, 2006, (accessed March 9, 2006)
Alligator, AmericanAlligator mississippiensisSAT
Barberry, truckeeBerberis (=mahonia) sonneiDR
Bidens, cuneateBidens cuneataDR
Broadbill, GuamMyiagra freycinetiD3A
Butterfly, Bahama swallowtailHeraclides andraemon bonhoteiDA
Cactus, Lloyd's hedgehogEchinocereus lloydiiDR
Cactus, spineless hedgehogEchinocereus triglochidiatus var. inermisDR
Cinquefoil, Robbins'Potentilla robbinsianaDM
Cisco, longjawCoregonus alpenaeD3A
Deer, Columbian white-tailed (Douglas County DPSb)Odocoileus virginianus leucurusDM
Dove, Palau groundGallicolumba canifronsDM
Duck, Mexican (U.S.A. only)Anas "diazi"DR
Falcon, American peregrineFalco peregrinus anatumDM
Falcon, Arctic peregrineFalco peregrinus tundriusDM
Flycatcher, Palau fantailRhipidura lepidaDM
Gambusia, AmistadGambusia amistadensisD3A
Globeberry, TumamocTumamoca macdougaliiDP
Goose, Aleutian CanadaBranta canadensis leucopareiaDM
Hedgehog cactus, purple spinedEchinocereus engelmannii var. purpureusDR
Kangaroo, eastern grayMacropus giganteusDM
Kangaroo, redMacropus rufusDM
Kangaroo, western grayMacropus fuliginosusDM
Mallard, MarianaAnas oustaletiD3A
Milk-vetch, RydbergAstragalus perianusDP
Monarch, Tinian (old world flycatcher)Monarcha takatsukasaeDM
Owl, PalauPyrroglaux podarginaDM
Pearlymussel, Sampson'sEpioblasma sampsoniD3A
Pelican, brown (U.S. Atlantic coast, Florida, Alabama)Pelecanus occidentalisDM
Pennyroyal, MckittrickHedeoma apiculatumDP
Pike, blueStizostedion vitreum glaucumD3A
Pupfish, TecopaCyprinodon nevadensis calidaeD3A
Shrew, Dismal Swamp southeasternSorex longirostris fisheriDP
Sparrow, dusky seasideAmmodramus maritimus nigrescensD3A
Sparrow, Santa Barbara songMelospiza melodia gramineaD3A
Sunflower, Eggert'sHelianthus eggertiiDM
Treefrog, pine barrensHyla andersoniiDP
Trout, coastal cutthroatOncorhynchus clarki clarkiDR
Turtle, Indian flap-shelledLissemys punctata punctataDO
Whale, gray (except where listed)Eschrichtius robustusDM
Woolly-star, Hoover'sEriastrum hooveriDP
  • Publish a final listing rule in the Federal Register—the listing becomes effective thirty days after publication, unless otherwise indicated.

After a species is listed, its condition and situation are reviewed at least every five years to decide whether it still requires government protection.


The ESA authorizes the Agencies to issue temporary emergency listings for species when evidence indicates an immediate and significant risk to the well-being of a species; for example, following a natural disaster. Two designations are possible: endangered emergency listing (EmE) and threatened emergency listing (EmT). The listing must be published in the Federal Register and is effective only for 240 days. During this time the normal status review procedure proceeds.

Petitioners also have the right under the ESA to ask the Agencies for an emergency listing for a species. In July 2005 a coalition of groups petitioned the Fish and Wildlife Service for an EmE listing for the rufus subspecies of the red knot, an imperiled shorebird found in New Jersey. The petitioners argued that the species faces imminent threats and "simply does not have the luxury of time to await the Service's normal status review." The FWS denied the petition claiming that recent population data show the bird's condition is improving and steps are already planned or taking place to protect the bird's status.

As of February 24, 2006, there were no emergency listings in effect for endangered or threatened species listed under the ESA.


Delisting occurs when a species is removed from the candidate list, proposed list, or final list of endangered and threatened species. Delisting takes place for a variety of reasons, as indicated by the "D" codes in Table 2.2. In general, delisting occurs when the agencies find that a species has recovered or become extinct or on various procedural grounds, including discovery of additional habitats or populations.

Listed species that have been delisted are shown in Table 2.4. Of the forty delisted species, fifteen recovered, nine became extinct, and the remainder had procedural issues.

According to the U.S. Fish and Wildlife Service, between September 1997 and February 2006 more than seventy candidate or proposed species were delisted; primarily because new information became available indicating that populations were greater or threats were less serious than originally believed. However, eight species were delisted because of extinction: four flowering plants and four insects.


Once a species becomes listed as endangered or threatened under the Endangered Species Act it is afforded the following protections:

  • Import, export, and interstate or foreign sales are prohibited without a special permit.
  • Taking is illegal—Taking is killing, harming, harassing, pursuing, or removing the species from the wild.
  • Federal agencies must conduct their activities in such a way as to conserve the species.
  • Federal agencies that manage lands and/or waters must consult with the U.S. Fish and Wildlife Service or National Marine Fisheries Service regarding conserving listed species in those habitats. Any activities funded or authorized by those federal agencies or carried out on lands or waters managed by them can not jeopardize the survival of the listed species.

Civil and criminal penalties can be levied for violations of these provisions. However, exemptions are granted for native peoples of Alaska that rely on certain endangered or threatened animals for food or other products needed for subsistence. In addition, section 4(d) of the Endangered Species Act allows the Fish and Wildlife Service to grant other exemptions from the "taking" rule for threatened species. For example, the gray wolf in Minnesota falls under a 4(d) rule that allows certain government agents to kill wolves that prey on domestic animals. The rule was created to prevent private citizens from performing wolf control to protect livestock. A 4(d) rule is commonly referred to as a "special rule" under the ESA.

Endangered species have different needs and require different conservation measures. Some fish are endangered only because of a history of overfishing. Halting or reducing fishing is sufficient for population recovery. In most cases, however, more active forms of intervention are necessary. The single most important conservation measure for many threatened and endangered species is habitat conservation or restoration. For some species, captive breeding followed by reintroduction into the wild may help increase numbers. In all cases, knowledge of the natural history of endangered species is essential to acquiring a better understanding of species' needs, as well as to the development of measures that will aid in conservation.

Critical Habitat

Under the Endangered Species Act the FWS or NMFS must decide whether critical habitat should be designated for a listed species. Critical habitat is specific geographical areas of land, water, and/or air space that contain features essential for the conservation of a listed species and that may require special management and protection. For example, these could be areas used for breeding, resting, and feeding. If the agencies decide that critical habitat should be designated, a proposal notice is published in the Federal Register for public comment. If it is decided that critical habitat is needed, then the final boundaries are published in the Federal Register.

The role of critical habitat is often misunderstood by the public. Critical habitat designation does not set up a refuge or sanctuary for a species in which no development can take place. It can provide additional protection for a specific geographical area that might not occur without the designation. For example, if the FWS determines that an area not currently occupied by a species is needed for species recovery and designates that area as critical habitat, any federal actions involving that area have to avoid adverse modifications. Critical habitat designation has no regulatory impact on private landowners unless they wish to take actions on their land that involve federal funding or permits.

The original ESA did not provide a time limit for the setting of critical habitat. In 1978 the law was amended to require that critical habitat be designated at the same time a species is listed. However, the designation is only required "when prudent." For example, the Fish and Wildlife Service or National Marine Fisheries Service can refuse to designate critical habitat for a species if doing so would publicize the specific locations of organisms known to be targets for illegal hunting or collection. Historically the agencies have broadly used the "when prudent" clause to justify not setting critical habitat for many listed species. This has been a very contentious issue between the government and conservation groups.

As of February 23, 2006, critical habitat had been designated for 473 species. This represents just over onethird of all U.S. species listed under the ESA. Plants make up more than half of the listed species for which critical habitat has been designated.

Experimental Populations

For a small number of species, primarily mammals, birds, fish, and aquatic invertebrates, recovery efforts include the introduction of individuals into new areas. Typically this is accomplished by moving a small group of imperiled animals from an established area to one or more other locations within their historical range of distribution.

Experimental populations of a species are not subject to the same rigorous protections under the Endangered Species Act as other members of the species. Experimental populations can be considered threatened, even if the rest of the species is listed as endangered. In addition, the FWS can designate an experimental population as essential or nonessential. A nonessential designation indicates that the survival of this population is not believed essential to the survival of the species as a whole. A nonessential experimental population (EXPN or XN) is treated under the law as if it is proposed for listing, not already listed. This results in less protection under the ESA.

As of February 2006 there were thirty-seven experimental populations listed under the ESA for thirty-three separate species. Clams and snails comprise more than half the animals represented. Notable experimental populations for mammals include the grizzly bear and gray wolf. Both have been reintroduced into portions of western states.

Recovery potential priority ranking system
Priority rankDegree of threatRecoverability potentialTaxonomy
Note: A species that is a monotypic genus is the only remaining species representing the entire genus.
source: "Table 2. Fish and Wildlife Service's Recovery Priority Ranking Schedule," in Endangered Species: Fish and Wildlife Service Generally Focuses Recovery Funding on High-Priority Species, But Needs to Periodically Assess Its Funding Decisions, U.S. Government Accountability Office, April 2005, (accessed February 25, 2006)
1HighHighMonotypic genus
4HighLowMonotypic genus
7ModerateHighMonotypic genus
10ModerateLowMonotypic genus
13LowHighMonotypic genus
16LowLowMonotypic genus

Recovery Plans

The ESA requires that a recovery plan be developed and implemented for every listed species unless "such a plan will not promote the conservation of the species." The Fish and Wildlife Service and National Marine Fisheries Service are directed to give priority to those species that are most likely to benefit from having a plan in place. The recovery potential of species is ranked from 1 to 18 as shown in Table 2.5. Low rankings indicate a greater likelihood that the species can be recovered. Priority is based on the degree of threat, potential for recovery, and taxonomy (genetic distinctiveness). In addition, rankings can be appended with the letter "c" when species recovery is in conflict with economic activities. Species with a "c" designation have higher priority than other species within the same numerical ranking.

Each recovery plan must include the following three elements:

  • Site-specific management actions to achieve the plan's goals
  • Objective and measurable criteria for determining when a species is recovered
  • Estimates of the amount of time and money that will be required to achieve recovery

Recovery plans include precisely defined milestones for recovery achievement. For example, recovery may be considered accomplished when a certain number of individuals is reached and specifically named threats are eliminated.

Notices regarding proposed new or revised recovery plans must be placed in the Federal Register so that public comment can be obtained and considered before a plan is finalized.

Incidental Take Permits and Habitat Conservation Plans

When the original ESA was passed it included exceptions that allowed "taking" of listed species only for scientific research or other conservation activities authorized by the act. In 1982 Congress added a provision in Section 10 of the ESA that allows "incidental take" of listed species of wildlife by nonfederal entities. Incidental take is defined as take that is incidental to, but not the purpose of, an otherwise lawful activity. Incidental taking cannot appreciably reduce the likelihood of the survival and recovery of listed species in the wild. The incidental take provision was added to allow private landowners some freedom to develop their land even if it provides habitat to listed species.

In order to obtain an incidental take permit, an applicant has to prepare a Habitat Conservation Plan (HCP). An HCP describes the impacts likely to result from the taking of the species and the measures the applicant will take to minimize and mitigate the impacts. HCPs are generally partnerships drawn up by people at the local level, working with officials from the Fish and Wildlife Service or the National Marine Fisheries Service. The plans frequently represent compromises between developers and environmentalists.

Included in the agreement is a "no surprise" provision that assures landowners or developers that the overall cost of species protection measures will be limited to what has been agreed to under the Habitat Conservation Plan. In return, landowners make a long-term commitment to conservation as negotiated in the HCP. Many HCPs include the preservation of significant areas of habitat for endangered species.

Although the HCP program was implemented in 1982, it was little used before 1992, with only fourteen permits issued in that time period. As of February 28, 2006, there were 446 HCPs in place covering dozens of species. More than half of the Habitat Conservation Plans were issued in FWS regions for the southwest and southeast states. By far, the animal with the most plans issued is the Houston toad with more than 200 HCPs in place. Information about HCPs is available in a database at the FWS Web site ( The database includes the locations covered by the plans as well as information on the applicants and the listed and unlisted species involved.


In a 2004 speech to the American Farm Bureau Federation, Gale Norton, Secretary of the Department of the Interior, described the Endangered Species Act as follows: "it is a powerful law designed for confrontation." Many confrontations over the law have taken place in the courts. The ESA includes provisions for civil lawsuits against government agencies alleged to be in violation of the ESA. Citizens can also sue if they believe the U.S. Fish and Wildlife Service has failed to perform actions required under the ESA or to compel the FWS to apply ESA prohibitions regarding "taking." Only two lawsuits were filed against the agency regarding the ESA between 1974 and 1991. Over the next decade more than three dozen suits were filed.

In Endangered Species Act: Successes and Challengesin Agency Collaboration and the Use of Scientific Information in the Decision Making Process (May 19, 2005), the Government Accountability Office (GAO) noted that the FWS had become "overburdened by litigation." Many of the lawsuits were filed by conservationist and animal groups regarding the listing process and designation of critical habitat. In 1992 a coalition of groups sued the Department of Interior charging that the listing process was proceeding too slowly. At that time more than 500 species were awaiting listing. The suit was settled out of court later that year when the FWS agreed to specific time limits for listings of the species at issue.

Designation of critical habitat has also been a contentious issue. In 1997 the Natural Resources Defense Council sued the Department of the Interior (DOI) over the long-standing policy of the U.S. Fish and Wildlife Service to avoid designating critical habitat under the "when prudent" clause. At that time the agency had set critical habitat for only approximately 10% of all listed species. The FWS lost the lawsuit, as well as many subsequent suits in the same vein. In 2000 the agency put a one-year hold on all work related to listing new species so that court-ordered critical habitat work could be tackled.

In 2004 the Fish and Wildlife Service lost a case that focused on the agency's decision to ignore petitions submitted for species that are candidate species. The lawsuit specifically dealt with the Gunnison sage grouse, a large ground-dwelling bird found only in parts of Colorado and Utah. In January 2000 a coalition of conservationist groups submitted a petition to the FWS on behalf of the species. The FWS responded that no action was needed on its part, because it planned to designate the species as a candidate species. This decision was in keeping with the agency's long-standing "Petition Management Guidance." In September 2000 the petitioning groups sued the agency claiming that the Guidance violated the intent of the ESA. In 2004 the U.S. District Court for the District of Columbia ruled against the FWS and ordered the agency to respond to petitions that had been submitted for more than 200 candidate species.

Since the 1990s the Fish and Wildlife Service has repeatedly complained that many of its decisions and activities are driven by court orders, rather than scientific priorities. Conservation and animal groups have taken advantage of ESA provisions that allow citizen involvement in petition submittals and lawsuits. Critics claim that the groups flood the FWS with petitions so that lawsuits can be brought when the agency is unable to respond in a timely manner. Environmentalists counter that the lawsuits are necessary, because the FWS fails to do the job assigned to the agency under the Endangered Species Act to protect imperiled species.


Various federal agencies spend money in support of the ESA. The primary spending agency is the U.S. Fish and Wildlife Service, a division of the Department of the Interior. For accounting purposes the federal government operates on a fiscal year that begins in October and runs through the end of September. Thus, fiscal year 2007 covers the time period of October 1, 2006, through September 30, 2007. Each year by the first Monday in February the President of the United States must present a proposed budget to the U.S. House of Representatives. This is the amount of money that the president estimates will be required to operate the federal government during the next fiscal year.

In February 2006 the president proposed a $10.5 billion budget for the Department of the Interior for fiscal year 2007. This amount is 3% less than the amount funded to the DOI for fiscal year 2006. Just under $1.3 billion was requested for the Fish and Wildlife Service for fiscal year 2007. An additional $808 million is available under permanent appropriations. (This is money allocated to the agency on a continuing basis, not requested each year). According to the FWS, most of the permanent appropriations for fiscal year 2007 will be turned over to the states for restoration and conservation of fish and wildlife resources.

A breakdown by FWS mission goal for the nearly $1.3 billion budget for fiscal year 2007 is shown in Figure 2.3. More than half the money is devoted to sustaining biological communities. Budget appropriations specific to endangered species are shown in Table 2.6 for fiscal years 2005 through 2007. For fiscal year 2007 just over $141 million is requested for endangered species programs. Most of the money is allocated to recovery programs ($65.9 million), followed by consultations with other agencies and groups ($49 million), listing activities ($17.8 million), and candidate species conservation ($8.1 million).

The Endangered Species Act requires the Department of the Interior to file an annual report detailing certain expenditures made for the conservation of threatened and endangered species under the act. The most recent report available was published in January 2005 and is titled Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004. The DOI collects spending data from other federal agencies and states receiving certain federal grants. The report indicates that $1.4 billion was spent during fiscal year 2004, broken down as follows:

U.S. Fish and Wildlife Service budgets for endangered species program, fiscal years 2005–07
[In thousands of dollars]
Appropriation: resource management, Change from by appropriation activity/subactivity2005 actual2006 enacted2007 requestChange from 2006 enacted
source: "Highlights of Budget Changes: Appropriation: Resource Management," in "Bureau Highlights: Fish and Wildlife Service," The Department of the Interior Fiscal Year 2007 Interior Budget in Brief, U.S. Department of the Interior, February 2, 2006, (accessed February 10, 2006)
Ecological services
Endangered species
    Candidate conservation9,1428,6198,063−556
        Subtotal, endangered species141,403147,808141,038−6,770
  • Specific individual species—$793 million
  • Land acquisition—$60 million
  • Other ESA expenses—$559 million

Other ESA expenses include salaries, operational expenses, and maintenance costs that are not assignable to a particular species. Total ESA expenditures for fiscal years 1994 through 2004 are shown in Figure 2.4 along with the number of listed species for each year.

Expenditures by Agency

The Department of the Interior reports that thirty-three federal agencies had ESA expenditures during fiscal year 2004; however, only thirty-one of the agencies were able to provide details on spending, as shown in Table 2.7. The federal agencies with the highest expenditures were the Department of Energy's Bonneville Power Administration ($309 million), FWS ($247 million), and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration or NOAA ($197 million). The National Marine Fisheries Service is an agency of NOAA and handles ESA management of marine mammals, such as whales and seals, and anadromous fish (which migrate between ocean and fresh waters). State spending under the Endangered Species Act during fiscal year 2004 amounted to $205 million.

The Bonneville Power Administration (BPA) operates an extensive electric transmission system throughout the northwest United States that provides electricity generated at federal dams and nonfederal facilities, including one nuclear power plant and a number of hydroelectric and wind energy plants. BPA is headquartered in Portland, Oregon. It is not funded by tax dollars, but by proceeds from the sale of electricity. Most BPA power comes from dams operated in the Columbia River basin. These waterways are also home to many endangered and threatened freshwater and anadromous fish species. BPA, the U.S. Army Corps of Engineers, and the Bureau of Reclamation operate the Federal Columbia River Power System and coordinate competing river uses, such as power generation, irrigation, flood control, navigation, recreation, and aquatic habitat.

Expenditures by Species

Table 2.8 shows the ten species with the highest reported expenditures under the Endangered Species Act in fiscal year 2004. The list is dominated by fish species. More than $161 million was spent on the Chinook salmon, followed by $117 million for the steelhead. Both species are anadromous and found in the waters of the Pacific Northwest. There are two marine (ocean-based) mammals on the top-ten list: the Steller sea lion and the right whale. The red-cockaded woodpecker is the only nonaquatic species in the top ten.

Table 2.9 shows the ten entities (species, subspecies, distinct population segment or evolutionarily significant unit) with the highest reported expenditures during fiscal year 2004. Eight of the ten entities are anadromous fish. The exceptions are the western population of the Steller sea lion and the bull trout (a freshwater fish) found in the coterminous United States. Anadromous fish are often designated by their season of upriver migration and the primary body of water in which migration takes place. The entity with the highest expenditure ($40.6 million) during fiscal year 2004 was the population of Chinook salmon that migrate up the Snake River from spring through summer.

How best to use the funds allocated to endangered species has been a contentious issue for years. Approximately half of the money allocated to individual species in fiscal year 2004 was spent on only about 1.5% of the listed species. In general, this disproportionate spending occurs because Congress and some states appropriate money for specific species. The DOI report Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004 notes the following benefits from this practice: "State and Federal natural resource managers use the public interest in these high-profile species to help protect other species in the same habitats or imperiled by the same threats. The species identified by Congress as deserving of specific appropriations are the same species that drive interest and participation in the considerable State and private sector efforts on behalf of all listed species."

Expenditures under the Endangered Species Act, fiscal year 2004
AgencySpecies totalLand totalTotal
aDHS is Department of Homeland Security.
bDOC is Department of Commerce.
cDOD is Department of Defense.
dDOE is Department of Energy.
eDOI is Department of the Interior.
fDOT is Department of Transportation.
gUSGA is United States Department of Agriculture.
source: "Table 4A. Species and Land Expenditures, Including Other ESA Expenses and Foreign Species, by Reporting Agency for FY2004," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, (accessed February 11, 2006)
DHSa Coast Guard$33,090,997$17,114$33,108,111
DHS Customs and Border Protection$334,000$0$334,000
DOCb National Oceanic and Atmospheric Administration$197,158,000$0$197,158,000
DODc Air Force$12,293,047$0$12,293,047
DOD Army$26,539,300$0$26,539,300
DOD Army Corps of Engineers$83,107,413$0$83,107,413
DOD Defense Logistics Agency$131,005$0$131,005
DOD Marine Corps$1,943,062$0$1,943,062
DOD Navy$4,988,842$0$4,988,842
DOEd Bonneville Power Administration$309,004,814$50,271$309,055,085
DOE Southwestern Power Administration$13,500$0$13,500
DOE Western Area Power Administration$6,492,268$0$6,492,268
DOIe Bureau of Indian Affairs$2,327,681$0$2,327,681
DOI Bureau of Land Management$21,153,074$412,170$21,565,244
DOI Bureau of Reclamation$93,786,700$1,851,000$95,637,700
DOI Minerals Management Service$2,707,347$0$2,707,347
DOI National Park Service$10,902,792$0$10,902,792
DOI US Geologic Survey$14,200,585$0$14,200,585
DOTf Federal Aviation Administration$202,295$0$202,295
DOT Federal Highway Administration$31,792,297$6,484,000$38,276,297
Environmental Protection Agency$5,262,500$0$5,262,500
Federal Communications Commission$27,500$0$27,500
Federal Energy Regulatory Commission$226,800$0$226,800
Nuclear Regulatory Commission$143,800$0$143,800
Smithsonian Institution$994,200$0$994,200
Tennessee Valley Authority$105,500$0$105,500
USDAg Animal and Plant Health Inspection Service$6,580,276$0$6,580,276
USDA Farm Service Agency$64,250$0$64,250
USDA Forest Service$35,652,300$0$35,652,300
USDA Natural Resources Conservation Service$30,016,143$19,798,572$49,814,715
US Fish and Wildlife Service$217,050,166$30,083,961$247,134,127
State governments$127,719,076$77,594,400$205,313,476

The number of species being added to the federal threatened and endangered species list is likely to continue to grow. Although vertebrate species dominated the list during the first years of the act, plants and invertebrate animals now make up a much greater proportion of listed species. (See Table 1.2 in Chapter 1.) These species are politically more difficult to defend than either mammals or birds, which are more inherently appealing to most Americans because of the "warm and fuzzy" factor. These circumstances raise questions about the continued feasibility of a species-by-species preservation strategy, and the FWS struggles under intense legal and political pressures to decide which species to protect first.


Opponents of the Endangered Species Act believe the law violates private property rights and stifles economic growth by curbing development. They also charge that environmental protection often results in the loss of jobs and business profits.

The ten listed species with the highest expenditures under the Endangered Species Act, fiscal year 2004
2004 rankSpecies (50CFRaPart17)StatusbTotal ($000s)2003 rank
aCode of Federal Regulations.
bE=endangered; T=threatened.
cAll subspecies, evolutionary significant units (ESUs), or distinct population segments (DPSs) combined.
source: "Table B. The Ten Species with the Highest Reported Expenditures in FY 2004," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, (accessed February 11, 2006)
1Salmon, chinookcE,T161,309.51
3Sea-lion, stellercE,T42,557.33
4Salmon, cohocT36,648.24
5Trout, bullT32,570.65
6Salmon, sockeyecE,T21,827.66
7Woodpecker, red-cockadedE14,125.110
8Sturgeon, pallidE13,370.234
9Salmon, chumcT13,257.97
10Whale, rightE12,369.68

One vocal critic of the ESA is Republican Congressman Richard Pombo of California. In 1996 Pombo coau-thored the book This Land Is Our Land: How to End the War on Private Property, in which he asserted that the ESA and other federal laws infringe upon private property rights. Since taking office in 1993, the Congressman has sponsored several bills calling for sweeping reforms of the ESA. The most recent legislation (H.R. 3824) was introduced in September 2005 and had ninety-five cosponsors. The bill calls for elimination of critical habitat designation, authorizes government payments for landowners prevented from carrying out planned developments, and grants greater decision-making powers to the Secretary of the Interior regarding the scientific data involved in ESA decisions. The bill was passed by the House, and was sent to the U.S. Senate for consideration.

In December 2005 Republican Senator Mike Crapo of Idaho and Democratic Senator Blanche Lincoln of Arkansas introduced Senate bill S. 2110, which also calls for major reforms of the Endangered Species Act. The Senate bill seeks greater collaboration between landowners and local, state, and federal officials in decision-making and offers incentives (such as tax breaks) for landowners to cooperate in recovery activities. In a press release Congressman Pombo expressed his support for the Senate bill noting, "The ESA must be updated to incorporate more than thirty years of lessons learned. It must be modernized to provide flexibility for innovation to achieve results ( As of May 2006 neither H.R. 3824 or S. 2110 had been passed by the Senate, but remained in committee.

The ten listed entities with the highest expenditures under the Endangered Species Act, fiscal year 2004
RankSpeciesPopulationStatus*2004 expenses
*E=endangered; T=threatened.
Note: Entity can be a species, subspecies, distinct population segment (DPS), or evolutionary significant unit (ESU).
source: Adapted from "Table A. The Ten Listed Entities with the Highest Reported Expenditures in FY 2004," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, (accessed February 11, 2006)
1Salmon, chinookSpring/summer, Snake RiverT$40,578,600
2Trout, bullU.S.A., coterminous, lower 48 statesT$32,570,600
3Sea-lion, stellerWestern populationE$31,746,200
4SteelheadSnake River basinT$28,203,300
5SteelheadMiddle Columbia RiverT$27,959,600
6Salmon, chinookFall, Snake RiverT$27,428,300
7Salmon, chinookPuget SoundT$24,084,900
8Salmon, cohoOregon, California populationsT$23,405,700
9Salmon, chinookSpring, upper Columbia RiverE$20,254,600
10Salmon, sockeyeU.S.A., Snake RiverE$17,550,200


Other critics argue, on the other hand, that the ESA is not enough. In May 2005 a group of ten prominent scientists sent a letter to the U.S. Senate in which they urged strengthening of the Act. The letter was spearheaded by Professors E. O. Wilson of Harvard University and Paul Ehrlich of Stanford University. It warns that Earth is facing an "extinction crisis" and that large numbers of species could be lost over the next few decades. The scientists note the importance of the ESA in U.S. efforts to preserve biological diversity and conclude, "Viewing our looming extinction crisis as a crisis for humans as well as wildlife, the importance of the Endangered Species Act takes on even greater significance. In the face of this crisis, we must strengthen the Act and broaden its protections, not weaken them" (

In March 2006 more than 5,700 U.S. scientists signed a letter to the U.S. Senate regarding concerns of the scientific community about proposed changes to the ESA. The letter highlights the historical successes of the Act as encouraging signs that progress is being made against the loss of imperiled species. It argues that the Act does not need a substantial overhaul, but a greater emphasis on implementation and use of objective scientific information in decision-making. The scientists wrote: "For species conservation to continue, it is imperative both that the scientific principles embodied in the Act are maintained, and that the Act is strengthened, fully implemented, and adequately funded" (

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