T he Endangered Species Act (ESA; P.L. 93-205 , 87 Stat. 884. 16 U.S.C. §§1531-1544) frequently receives significant congressional attention. It offers comprehensive protection for species identified as endangered or threatened with extinction. Over the years, the power of this protection has ignited calls for greater bounds on this power, as well as assertions of its lax implementation. The following discussion provides an overview and background on the various features of the ESA that contribute to its legal stature and yet spark an ongoing debate over its implementation. The ESA is a comprehensive attempt to provide legal protection to identified species and to consider habitat protection as an integral part of that effort. It is administered primarily by the Fish and Wildlife Service (FWS) for terrestrial and freshwater species, but also by the National Marine Fisheries Service (NMFS) for certain marine species. Under the ESA, individual species of plants and animals (both vertebrate and invertebrate) can be listed as either "endangered" or "threatened" according to assessments of the risk of their extinction. Once a species is listed, powerful legal tools are available to aid the recovery of the species and to protect its habitat. Among these legal tools are the ESA's prohibition of unpermitted "take" (e.g., killing, capturing, or harming) of endangered species and its requirement that agencies, in consultation with FWS or NMFS as applicable, ensure that their actions are not likely to jeopardize the continued existence of listed species or result in destruction or adverse modification of critical habitat. (See "Take" and " Critical Habitat ," below.) As of August 24, 2016, a total of 2,266 species of animals and plants had been listed as either endangered or threatened; 1,593 of these species occur in the United States and its territories, and the remainder occur only in other countries. Of the U.S. species, 1,156 are covered by recovery plans. The ESA was passed in 1973, but was preceded by simpler acts to conserve species in 1966 and 1969. It has been amended on numerous occasions since then: 1976, 1977, 1978, 1979, 1980, 1982, 1988, and 2003. The authorization for funding under the ESA expired on October 1, 1992, although Congress has appropriated funds in each succeeding fiscal year. ESA prohibitions and penalties remain in effect regardless of appropriations. A stated purpose of the ESA is to "provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved." While the ESA plays an important role in protecting species, it also can become a surrogate battleground in debates whose primary focus is the allocation of scarce or diminishing lands, waters, or resources. The surrogate role is especially likely because other laws often lack the strict substantive provisions that Congress included in the ESA (see " Major Provisions " sections, below). There can be economic interests on multiple sides of some vanishing species issues. Like the miners' canaries signaling a scarce resource (safe air supply), declining species are often symptoms of resource scarcities and altered ecosystems. Examples of such resource controversies include the Tellico Dam (hydropower development and construction jobs versus farmland protection and tribal graves, as well as the endangered snail darter); and Northwest timber harvest (protection of logging jobs and communities versus commercial and sport fishing, recreation, and ecosystem protection, as well as salmon and spotted owls). The worldwide debate over global climate change (fossil fuels, carbon dioxide emission levels, shoreline erosion, melting glaciers, traditional jobs, etc.) has found an avatar in the polar bear. Tensions over the ESA have increased as species have been added to the protected list, and as the greater demands of a growing economy and human population have affected species' habitats. Both Congress and the executive branch have sought to lessen these tensions by, among other things, tailoring application of the ESA for particular circumstances. The ESA's critics contend that neither the ESA nor administrative efforts go far enough in accommodating needs other than species conservation, while the ESA's defenders counter that it only balances what they see as an inherent bias toward development in other governmental laws and policies. Debate on the ESA splits largely along demographic lines. While most demographic groups support species conservation to some degree, that support is stronger among urban and suburban populations and less so in rural areas, and is stronger among those along the coasts and less so in central and mountain states. Sport hunters and anglers seem divided on the issue. Native Americans, as a group often dependent on natural resources (e.g., fish), are frequently involved in ESA issues and often support the survival of listed species. Groups opposing strong protections for listed species usually assert that jobs will be lost if conservation measures are stringent, but those seeking strong protections often claim that jobs will be lost if they are not. It is also noteworthy that, while the debate often centers on jobs and biology, people on both sides claim ethical support for their positions, and many religious groups participate in the debate. In addition, some industries (e.g., logging and land development) generally see the ESA as a serious problem, while others (e.g., some commercial fishing and many recreation interests) see it as generally supporting their interests. There is a difference between the statutory authority to carry out an action and the authorization of appropriations within a statute. The ESA contains both statutory authority for certain activities and a provision authorizing approp riations. Section 15 (16 U.S.C. §1542) is the provision authorizing appropriations—through FY1992. Even though Congress has continued to appropriate funding for ESA, the following questions are sometimes raised: (1) are the act's various prohibitions and authorities still in effect; (2) what are the House and Senate rules concerning appropriating in the absence of a current authorization; and (3) what would be the effect of a failure to appropriate funds for the agencies (primarily for FWS and NMFS, but also Coast Guard, and Secretaries of Agriculture and Treasury) to carry out their responsibilities under the ESA? Because the authorization for appropriations expired in FY1992, it is sometimes said that the ESA is not authorized. However, that does not mean that the agencies lack authority to conduct actions (Sections 4, 6-8, 10, and 11; 16 U.S.C. §§1533, 1535-1537, 1539 and 1540), or that prohibitions within the act are no longer enforceable (Section 9; 16 U.S.C. §1538). Those statutory provisions continue to be law, even if no money were appropriated. The expiration of a provision authorizing appropriations does not end the statutory obligations created by that law. The U.S. Supreme Court has long held that "the mere failure of Congress to appropriate funds, without further words modifying or repealing, expressly or by clear implication, the substantive law, does not in and of itself defeat a Government obligation created by statute." Moreover, Section 11(g) (16 U.S.C. §1540(g)) "allows any citizen to commence a civil suit on his own behalf" on various broad, specified provisions of the act. This option would still be available, regardless of agency funding. Consequently, persons carrying out acts prohibited by ESA might still face citizen suits, even if FWS or NMFS were temporarily unable to carry out their enforcement responsibilities due to lack of funds. The possibility of citizen suits could have the potential to dissuade many parties from carrying out such prohibited acts. Both the House and Senate have long-standing internal rules that distinguish between authorizations and appropriations and provide for the separate consideration of legislation containing these types of provisions. This distinction, however, exists for the convenience of Congress and does not affect a measure's statutory force when enacted into law. Either chamber can choose to observe or waive its rules during the course of the legislative process. Clause 2 of House Rule XXI prohibits consideration of measures or amendments that contain unauthorized appropriations. Further, clause 5 of House Rule XXII prohibits consideration of conference reports containing unauthorized appropriations. House rules additionally prohibit appropriations in legislation not reported by the Committee on Appropriations (Rule XXI, clause 4), amendments thereto (Rule XXI, clause 4), or conference reports (Rule XXII, clause 5). These rules are enforced via points of order on the floor. The House Rules Committee, however, may report a special rule that sets procedural parameters for the consideration of an appropriations measure. This can include the waiver of rules prohibiting unauthorized appropriations for any specified floor amendments, as well as the measure itself. Special rules can also waive points of order against provisions in a conference report on an appropriations measure. In order for these waivers to occur, the House must adopt a special rule prior to consideration of the measure or conference report. Senate rules also distinguish between authorizations and appropriations and prohibit unauthorized appropriations in both committee and floor amendments, except in specified circumstances (Rule XVI, paragraphs 2 and 4). This prohibition does not apply to conference reports. This rule is enforced via points of order during consideration, but its application may be waived by unanimous consent. The practical effects of a lapse in funding would be mixed from the standpoint of supporters and critics of existing law. Some of the areas which might be affected during the period of the lapse are listed below. (These activities are described in the remainder of the report.) No interagency consultations to approve agency actions (e.g., on construction of highways or dams, siting of pipelines on federal lands, or offshore energy drilling; see " Consultation "), nor issuance of incidental take statements to shield agencies from citizen suits; No species listed or delisted, potentially increasing lawsuits when Services fail to meet the listing deadlines in Section 4 (see " Listings "); No critical habitat designated, revised, or removed from designation, potentially increasing lawsuits when Services fail to meet deadlines (see " Critical Habitat "); No issuance of incidental take permits for nonfederal actions (see " Permits for Nonfederal Actions "); No or reduced inspections of incoming cargo for violations of species listed under the Convention on International Trade in Endangered Species (CITES) (see " International Applications of the ESA "); No fulfillment of other obligations under CITES; No monitoring of candidate species (see " Candidate Species "); No federal enforcement of prohibitions on taking listed species or adverse modification of critical habitat (though citizen suits under the ESA still possible; see " Prohibitions, Penalties "); No acquisition of habitat for listed species (because money for administering purchases would not be available; see " Land Acquisition "); No state grants for conservation of listed or candidate species (see " Land Acquisition "); and No ability under Section 7 (e)-(p) to exempt agency actions from jeopardy opinions (see " Exemptions "). The last major effort to end all funding for the ESA occurred in the 104 th Congress. Interest at the time was centered on a desire to eliminate a major source of conflict in projects such as those cited above. However, because of the type of effects just listed, the effort was abandoned, although funding for the listing of new species was temporarily halted. The answer to this question depends very much on the choice of measurement. A major goal of the ESA is the recovery of species to the point at which the protection of the ESA is no longer necessary. If this is the standard, the ESA might be considered a failure, because only 34 species have been delisted due to recovery, as of July 25, 2016. Ten species have become extinct since their listing; 8 have been delisted due to scientific reclassification of the species; and 11 have been delisted due to improved data, changes in the law, or improved scientific understanding. In the case of the species now believed extinct, some were originally listed to protect any last remaining few that might have been alive at the time of listing. It can be quite difficult to prove whether extraordinarily rare species are simply that, or in fact are already extinct. For example, two bird species, the ivory-billed woodpecker and the Eskimo curlew, are both listed as endangered, though confirmed sightings are so rare or so far in the past that these birds may actually be extinct; proving a negative (i.e., that such species do not exist any longer) is quite difficult. Rare species are, by definition, hard to find. Even so, because some scientific studies have demonstrated that most species are listed only once they are very depleted (e.g., median population of about 400 animals for vertebrates listed as endangered according to one study), another measure of effectiveness might be the number of species that have stabilized or increased their populations, even if the species is not actually delisted. If this is the standard, the ESA could be considered a success, since a relatively large number (41% of listed species according to one study) have improved or stabilized their population levels. One could also ask what species might have become extinct if there were no ESA: some species (e.g., red wolves and California condors) might not exist at all without the ESA protection, and this too might be considered a measure of success, even though the species are still rare. The authors are unaware of comprehensive studies regarding the likely status of rare species were there no ESA, but some species (e.g., some salmon populations, Florida panthers, California condors, and plants of very narrow ranges) might have declined further, from exceptional rarity to extinction, if ESA did not exist. Scientific information and analysis are pillars of ESA actions and enforcement. Three issues form the scientific background of the ESA: What are the leading causes of extinction? Is extinction normal? How do current extinction rates compare to background levels of extinction? Until the mid-20 th century, the focus of the extinction debate was on losses due to over-exploitation, generally through hunting, trapping, or fishing. The poster species of the debate were passenger pigeons, tigers, wolves, and other well-known animals. But during the 20 th century, a shift occurred. The vast majority of species, including those for which actual removal from the wild was probably an early factor in their decline, now are generally also at risk due to habitat loss. Habitats that have been reduced to a small fraction of their former extent include tall-grass prairie, fresh and salt water wetlands, old growth forests of most types, free-flowing rivers, coral reefs, undisturbed sandy beaches, and others. Global climate change is another contributor to habitat loss, acting in concert with other factors influencing population levels. Another high-ranking factor in the demise of many species is the introduction of nonnative invasive species. Nonnative species can be disease vectors or parasites (e.g., avian malaria in Hawaii, chytrid fungus attacking amphibians in much of the world, or Asian long-horned beetles in North America), predators (e.g., brown tree snakes in Guam and Hawaii), or competitors (e.g., barred owls in the Pacific Northwest or snakeheads in the Potomac River). The gradual homogenization of the world's flora and fauna has led to a demise of many species. Finally, many species are threatened by multiple factors, and some species decline for no obvious reason. If extinction is normal, some argue that there is no need for the government to intervene to halt this natural process. But is it normal? Geological evidence shows that the vast majority of species that have ever lived on Earth are now extinct—an observation uncontested by paleontologists. However, many scientists are concerned that the current rate of extinction exceeds background extinction rates over time. But calculating current rates of extinction, much less making comparisons with the geologic past, is extremely difficult. Current estimates of total numbers of species range from 3.5 million to 100 million, with 10-30 million being commonly accepted numbers. If scientists are unsure of how many species exist, it is naturally difficult to estimate how fast they are going extinct, and whether current extinction rates exceed background extinction rates. Consequently, scientists use very conservative assumptions to make these estimates. The resulting extinction rates (17,000 species per year being a typical estimate) may still seem astonishingly large, in part because the public is generally unaware of the huge number of species in groups to which many people pay little or no attention (e.g., beetles, marine invertebrates, fish), and the large number of species estimated on Earth. Widely diverse methods of calculating extinction rates all suggest that current rates exceed background rates. Normal rates are thought to be from 1 to 10 species for every 10 million species per year. (That is, if there are 20 million species now, background levels would be about 2 to 20 species extinctions per year.) Common estimates of current extinction rates range from 100 to 10,000 times such background rates—roughly comparable to the five great episodes of extinction in the geologic past. Critics most frequently question these calculations by stressing uncertainties, rather than citing specific factual errors. This criticism is not surprising, since each step in these calculations contains uncertainties (e.g., estimating the number of existing species). Most biologists counter by noting that similar numbers are generated in studies of widely different groups by a variety of scientists using different methods; robust results (i.e., similar results from the testing of a hypothesis in a variety of ways) are usually considered scientifically sound. Once extinct, a species cannot be revived. But, faced with high rates of extinction, some might argue that a return to an equal number of species, even if those species are different, would constitute a recovery of sorts. Evolution continues, so new species may evolve that are better adapted to new conditions. How long would such a replacement/recovery take? Examining the geologic record after major extinction episodes, some scientists estimate that recovery to approximately equal numbers of (different) species took up to 25 million years for the most severe extinction events. Thus, if the current extinction rate and recovery rate are comparable to past rates, the return to species numbers of the pre-historic era would take at least several million years. The following are the major provisions of the ESA in the order they appear in the U.S. Code . An endangered species is defined as "any species which is in danger of extinction throughout all or a significant portion of its range." A threatened species is defined 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 ESA does not rely on a numerical standard; such a standard would not reflect the wide variety of many species' biology. (For example, a population of 10,000 butterflies, all confined to one mountaintop, would be at greater risk than 10,000 butterflies scattered over dozens of mountaintops.) The protection of the ESA extends to all species and subspecies of animals (not just birds and mammals), although for vertebrates, further protection can be given for distinct population segments within a species, and not just the species as a whole. More limited protection is available for plant species under the ESA. There is no protection afforded under the ESA for organisms (e.g., Eubacteria, Archaea, viruses) considered neither animal nor plant. The term "take" under the ESA means "to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct." (Harassment and harm are further defined by regulation at 50 C.F.R. §17.3.) There has been controversy over the extent to which the prohibition on taking may include habitat modification. A 1995 Supreme Court decision held that the inclusion of significant habitat modification where it actually kills or injures wildlife was a reasonable interpretation of the term "harm" in the law. The Secretary of the Interior manages and administers most listed species through FWS. Marine species (including most marine mammals) and anadromous fish are the responsibility of the Secretary of Commerce, acting through NMFS. The law assigns the major role to the Secretary of the Interior (all references to "Secretary" below are to the Secretary of the Interior unless otherwise stated) and provides for the relationship of the two Secretaries and their respective powers. Species may be listed on the initiative of the appropriate Secretary or, more commonly, by petition from an individual, group, or state agency. The Secretary must decide whether to list the species based only on the best available scientific and commercial information, after an extensive series of procedural steps to ensure public participation and the collection of relevant information. At this point, the Secretary may not consider the economic effects that listing may have on the area where the species occurs, although economic considerations are part of the critical habitat determination. This section (§4(b)(1)(A)) is the only part of the ESA where economic considerations are expressly forbidden, because Congress directed that listing be fundamentally a scientific question: is the continued existence of the species threatened or endangered? A species may be designated as either endangered or threatened, depending on the severity of its decline and threats to its continued survival. Under Section 3 of the ESA, an endangered species is a species that is "in danger of extinction throughout all or a significant portion of its range." A threatened species is defined as a species "likely to become endangered within the foreseeable future throughout all or a significant portion of its range." Because the ESA defines species as a species, a subspecies, or—for vertebrates only—a "distinct population segment," there is some flexibility as to how to provide different levels of protection to less than a whole species. The phrase "all or a significant portion of its range" has had different interpretations. The Department of the Interior (DOI) at one time interpreted the phrase to find that only a species in danger of extinction throughout all of its range was truly endangered. Under this interpretation, a species at risk of extinction only in a significant portion of its range would not be considered endangered. With only two exceptions, every court that considered the issue found DOI's interpretation violated the ESA, including one federal court of appeals. In 2014, FWS and NMFS issued their joint interpretation of the phrase. Under their interpretation, a portion of a species' range is significant if the species is not currently endangered or threatened throughout its range, but the portion's contribution to the viability of the species is so important that, without the members in that portion, the species would be in danger of extinction, or likely to become so in the foreseeable future, throughout all of its range. The interpretation also states that the range of a species is the area in which a species currently exists, not the historical range where the species once existed. The determination of whether a species should be listed as endangered or threatened must be based on several scientific factors related to a species and threats to its continuance. The ESA expressly states that listing determinations are to be made "solely on the basis of the best scientific and commercial data available." The word "solely" was added in the 1982 amendments to the ESA to clarify that the determination of endangered or threatened status was intended to be made without reference to its potential economic impacts. Observers have compared the decision of whether to list a species to diagnosing whether a patient has a potentially fatal disease: the diagnosis should be a strictly scientific decision, but other factors can be considered later in deciding how to treat the disease. In discussing the addition of the word "solely," a committee report stated: The principal purpose of the amendments to Section 4 is to ensure that decisions pertaining to the listing and delisting of species are based solely upon biological criteria and to prevent non-biological considerations from affecting such decisions.... [T]he legislation requires that the Secretary base his determinations regarding the listing or delisting of species "solely" on the basis of the best scientific and commercial data available to him. The addition of the word "solely" is intended to remove from the process of the listing or delisting of species any factor not related to the biological status of the species. The Committee strongly believes that economic considerations have no relevance to determinations regarding the status of species.... The only alternatives involved in the listing of species are whether the species should be listed as endangered or threatened or not listed at all. Applying economic criteria to the analysis of these alternatives and to any phase of the species listing process is applying economics to the determinations made under Section 4 of the Act and is specifically rejected by the inclusion of the word "solely" in this legislation. In summary, the ESA makes clear that the question of whether a species is endangered or threatened is a scientific decision in which economic factors must not play a part. Even so, once this determination is made, nothing in the ESA prevents choosing conservation methods that will lower costs to society, industry, or landowners, as long as the chosen methods still achieve conservation goals. As noted above, species listings are often initiated by petition, although petitions to change the status of a species (uplist or downlist) or to delist a species may also be filed and are subject to the same standards and deadlines. The ESA requires that "to the maximum extent practicable," FWS and NMFS must make an initial determination within 90 days of receiving a petition from any interested person (often, in practice, an environmental advocacy group). The 90-day determination assesses whether the petition presents substantial scientific or commercial information indicating that the petitioned action may be warranted. If so, the agency has 12 months to conduct a status review of the candidate species and find that (1) the action is not warranted; (2) the action is warranted and a listing proposal will be promptly published; or (3) the action is warranted but precluded by higher priority species for listing. A "warranted but precluded" finding must be reevaluated annually. Lawsuits have been brought against the agencies for failure to meet these deadlines, particularly in the face of increasing numbers of petitions. Several of these lawsuits were settled in 2011, setting deadlines for listing determinations on hundreds of species. As of August 2016, FWS had received more than 160 ESA petitions, of which more than 100 were for listing; other petitions have requested changes to listing or other actions. The question may arise as to the responsibilities of the federal government toward a species that is proposed for listing but has not yet been listed. This question could be important because there may be a significant time between the proposal for listing and the actual listing, during which time federal agencies could be faced with decisions on management actions of various types. Under current law, an agency must "confer" with the appropriate Secretary on any agency action that is likely to jeopardize the continued existence of any species proposed to be listed or to destroy or adversely modify critical habitat proposed to be designated for such species. The implementing regulations state that the conference is designed to assist the federal agency and the applicant (if any) in identifying and resolving potential conflicts at an early stage in the planning process. The conference process that applies to species proposed for listing is distinct from the consultation process that applies to listed species. The conference is intended to be less formal and to permit FWS or NMFS to advise an agency on ways to minimize or avoid adverse effects. The agency may choose to follow the more complete and formal process even at the proposed listing stage to avoid duplication of effort later. The ESA states that the conference stage does not require a limitation on the irreversible or irretrievable commitment of resources by agency action that would foreclose reasonable and prudent alternative measures. Once a species is listed, an agency will have definite responsibilities and an agency might consider it prudent at the proposed listing stage both to avoid harm to a precarious species and to avoid possible liability for compensation arising from agency actions creating private rights that later cannot be exercised. For example, an agency might choose to avoid holding timber sales in an area containing a proposed species. The relevant Secretary must monitor candidate species and prevent a significant risk to the well-being of any such species. A candidate species is "any species being considered by the Secretary for listing as an endangered or threatened species, but not yet the subject of a proposed rule." As of August 24, 2016, there were 58 candidate species. While a species is a candidate for listing, federal agencies and other entities may pursue a strategy of working to improve the status of a species to avoid a listing proposal at some future date. Federal agencies may develop a candidate conservation agreement (CCA) with FWS or NMFS to take specified actions to conserve a species. Nonfederal landowners may pursue a candidate conservation agreement with assurances (CCAA). Under a CCAA, a landowner may agree to carry out certain actions that will improve conservation of the species, with the assurance that, as long as the agreed actions are carried out, there will be no required change if any candidate species covered under the conservation agreement is subsequently listed as threatened or endangered. If a species is proposed for listing under the ESA, the Secretary must publish the proposed regulation in the Federal Register ; give notice to state agencies and counties where the species is thought to occur; invite those governments to submit comments on the proposal; give notice, if practical, to foreign countries where the species occurs or whose citizens harvest the species on the high seas; notify relevant professional societies; publish a summary of the regulation locally; and hold a public hearing in the area where the species is found. As of August 24, 2016, 73 species were proposed for listing. Federal agencies must confer with the appropriate Secretary on actions likely to jeopardize the continued existence of candidate species, but agencies need not limit commitments of resources. In the interval between a proposal and a listing decision, the Secretary must monitor the status of a candidate species and, if any emergency poses a significant risk to the well-being of the species, promptly list it. Some steps in the normal listing process may be skipped for emergency listings. The Secretary may promulgate special regulations to address conserving those species listed as threatened. Protections and recovery measures for a particular threatened species can be carefully tailored to particular situations, as was done, for example, with respect to the threatened northern long-eared bat and the polar bear. A federal regulation also clarifies that a threatened species for which a special rule has not been promulgated enjoys the same protections as endangered species. A distinct population segment (DPS) under the ESA refers to a portion of a listed species, separated from the rest of the species by genetic distinction and range. By definition, only vertebrates may be designated as a DPS. A 1996 policy contains the criteria that must be met for designating a DPS: the population must be discrete and significant. Discreteness is based on separation from other groups of its kind. To be significant, the segment's demise must be an important loss of genetic diversity. Once the appropriate service finds that a DPS exists, the DPS's protection status is determined using the same criteria as for other listings. If the DPS is found to be threatened, special rules under Section 4(d) of the ESA may be written. One DPS designation that has prompted extensive litigation is that of the gray wolf, with each DPS established since 2003 vacated by courts. In one decision, a court said that FWS had not used the DPS process correctly when it created a DPS and removed all protection for that DPS at the same time. NMFS developed the concept of evolutionarily significant units (ESUs) as a way of interpreting the "distinct population segment" language in Section 3(16) of the ESA. ESUs generally include multiple (often as many as 20 to 30) populations or stocks and are intended to identify important groups of salmon populations. As of July 25, 2016, 28 ESUs of salmon and steelhead trout along the Pacific coast were listed as either endangered or threatened under the ESA. The ESU concept has been problematic to some because it is not specifically scientifically based—the term was not used or recognized before NMFS invented it. NMFS chose to use the ESU concept for both policy and scientific reasons: the stock level was not practical because there are thousands of distinct stocks, and the full species level would not distinguish among distinct population segments that have different situations. The question of whether hatchery fish may be assigned to an ESU, thereby augmenting an ESU's population count, has been particularly controversial. In 1982, Congress added the concept of experimental populations to the ESA as a way of reintroducing a species to its historic range without risking severe restrictions on the use of private and public land in the area. Two criteria must be met to qualify for reintroduction as an experimental population. First, the service must have authorized the release of the population. Second, the population must be wholly separate geographically from other animals of that species. Congress required the separation so that the introduced population could be clearly distinguished. An experimental population's protected status is determined differently from that of a DPS or other species. If the experimental population is in imminent danger of extinction, it is deemed essential. (Currently, no experimental populations are designated as essential.) Otherwise, the experimental population is treated as nonessential and is considered threatened. Special regulations under Section 4 of the ESA are made regarding these populations and can include rules for taking the species. Unless the experimental population is in a national wildlife refuge or a national park, no Section 7 consultation is required for an agency action that may take a member of the population. (See " Consultation ," below.) Critical habitat is not designated for nonessential experimental populations. The processes for delisting, uplisting, or downlisting a species from the Lists of Endangered and Threatened Wildlife and Plants are the same as the processes for listing. Delisting is removing a species from the lists. Downlisting is reclassifying a species from endangered to threatened, and uplisting is the reverse. The Secretary of the Interior may initiate a change in the status of listed species. Alternatively, after receiving a substantive petition for any change in listing status, the Secretary is to review the species' status. The determination to delist, uplist, or downlist a species must be made "solely on the basis of the best scientific and commercial data available" and "without reference to possible economic or other impacts." The statute and regulations also mandate that, at least once every five years, there be a review of each species already listed to determine whether it should be removed from the list, changed from endangered to threatened, or changed from threatened to endangered. Critical habitat, as defined, includes not only geographic areas occupied by the species at the time of listing, but also areas outside that geographic area, if the Secretary determines that such additional areas are essential for the conservation of the species. When a species is listed, the Secretary must also designate critical habitat. If the publication of this information is not "prudent" because it would harm the species (e.g., by encouraging vandals or collectors), the Secretary may choose not to designate critical habitat. The Secretary may also postpone designation for as long as one year if the information is not determinable. Eventually, with the exception of designations that would not be prudent, critical habitat is to be designated. As of July 25, 2016, critical habitat had been designated for 758 listed species, or 47.5% of the 1,596 listed domestic animal and plant species. Any area, whether or not federally owned, may be designated as critical habitat, but private land is affected by critical habitat designation only if some federal action (e.g., a license, loan, or permit) is also involved. Federal agencies must avoid "destruction or adverse modification" of critical habitat, either through their direct action or activities that they approve or fund. If the Secretary designates critical habitat, the Secretary must do so on the basis of the best scientific data available and after taking into consideration the economic impact, and any other relevant impact, of specifying any particular area as critical habitat. The Secretary may exclude any area from critical habitat if he determines that the benefits of such exclusion outweigh the benefits of specifying such area as part of the critical habitat, unless he determines, based on the best scientific and commercial data available, that the failure to designate such area as critical habitat will result in the extinction of the species concerned. Therefore, although economic factors are not to be considered in the listing of a species as endangered or threatened, economic factors must be considered in the designation of critical habitat. Some habitat areas may be excluded from designation based on such concerns, unless the failure to designate habitat would result in the extinction of the species. Although avoiding adverse modification of critical habitat is an express obligation only for federal agencies and actions, it is frequently misunderstood by the public as the major restriction on a private landowner's authority to manage land. However, restrictions on use of private land come primarily from the ESA's prohibition on taking (as defined) of listed species. Only occasionally—when some federal nexus is present—are these restrictions due to any additional strictures resulting from designated critical habitat. Moreover, the ESA provides significantly fewer restrictions on the nonfederal taking of listed plants than listed animals. P.L. 108-136 amended the ESA to add a provision specifying that the Secretary shall not designate critical habitat on lands controlled by the Defense Department, if those lands are subject to an Integrated Natural Resource Management Plan (INRMP) under the Sikes Act (16 U.S.C. §670a). The provision was subject to the Secretary's determination, in writing, that the INRMP provided "a benefit" to the lands which might otherwise have been designated as critical habitat. In addition, the Secretary was directed to take national security into consideration in designating critical habitat. These provisions were added in response to assertions that designated critical habitat on some military lands interfered with military training and readiness activities. For more than 20 years, Administrations have supported and Congress has approved restrictions on FWS's ability to designate critical habitat under the ESA through the appropriations process. According to FWS, critical habitat designation shows its greatest conservation benefit when it includes areas not currently occupied by the species; these areas may be important as connecting corridors between populations or as areas in which new populations may be reintroduced. In an announcement on October 22, 1999, FWS placed designation of critical habitat at the lowest priority in its listing budget and stated that the agency could not comply with all of the ESA's demands under its budget constraints. Conservation groups saw a contradiction between that claim and the agency's repeated decision not to request increased funds for listing, together with the agency's requests that Congress place a special cap on funding for designation of critical habitat. These funding restrictions on designation of critical habitat have remained in all subsequent appropriations bills. FWS has been sued frequently for its failure to designate critical habitat, and the agency consistently loses such suits. In the agency's view, critical habitat offers little protection for a species beyond that already available under the listing process and thus the expense of designation, combined with the perception of a small margin of additional conservation benefit, make critical habitat requirements a poor use of scarce budgetary resources, especially if the public views critical habitat as the major regulatory impact of the ESA rather than as a supplement to the ESA's prohibition on "taking" a listed species. The designation of critical habitat may provide additional protection for listed species in the context of federal actions. Federal agencies must consider whether their actions are likely to destroy or adversely modify critical habitat under the Section 7 consultation provisions, meaning this protection is not available for species without such designated habitat. The FWS previously disagreed that extra protection is provided in this way, saying that it would be rare that a habitat would be harmed in this way without the species also being put in jeopardy. Therefore, according to FWS, designated critical habitat does not provide additional protection from federal actions because the jeopardy consideration would provide the necessary protection. This conclusion was based in part on the FWS regulatory definition of "destroy or adversely modify," which required that the federal action must "appreciably diminish the value of critical habitat for both the survival and recovery of a listed species." However, it was argued that the definition improperly shifted the focus from recovery of the species to survival of the species. Several federal courts of appeal agreed, holding that the definition was contrary to the ESA because it ignored the recovery goal of the law. This was finally changed in February 2016. The Federal Register notice said: After the Ninth Circuit's decision, the Services each issued guidance to discontinue the use of the 1986 definition …. Specifically, in evaluating an action's effects on critical habitat as part of interagency consultation, the Services began directly applying the definition of "conservation" as set out in the Act. … The definition now in 50 C.F.R. 402.02 gives greater emphasis to the act's focus on recovery: Destruction or adverse modification means a direct or indirect alteration that appreciably diminishes the value of critical habitat for the conservation of a listed species. Such alterations may include, but are not limited to, those that alter the physical or biological features essential to the conservation of a species or that preclude or significantly delay development of such features. The appropriate Secretary must develop recovery plans for the conservation and survival of listed species. Recovery plans to date tend to cover birds and mammals, but a 1988 ESA amendment prohibits the Secretary from favoring particular taxonomic groups. The ESA and its regulations provide little detail on the requirements for recovery plans, nor are these plans binding on federal agencies or others. The resulting hortatory nature of these plans has been widely criticized. As of August 24, 2016, there were recovery plans for 1,156 U.S. species. Land may be acquired to conserve (recover) endangered and threatened species. Money from the Land and Water Conservation Fund (LWCF) may be appropriated for this acquisition. LWCF is a federal fund derived primarily from receipts from offshore oil and gas leases, and is used primarily for land acquisition for four agencies charged with managing most federal lands. Under the ESA, the appropriate Secretary must cooperate with the states in conserving protected species and must enter into cooperative agreements to assist states in their endangered species programs, if the programs meet certain specified standards. If there is a cooperative agreement, the states may receive federal funds to implement the program, but the states must normally provide a minimum 25% matching amount. The 1988 ESA amendments created a fund to provide for the state grants, including land acquisition and planning assistance. While the authorized size of the fund is determined according to a formula, money from the fund still requires annual appropriation. For FY2016, Congress appropriated $53.5 million for cooperative activities with states and territories. If federal actions or actions of nonfederal parties that require federal approvals, permits, or funding might adversely affect a listed species as determined by the Secretary, the federal action agencies must complete a biological assessment (BA). The assessment is used to determine whether formal consultation is necessary. This assessment also is to be based on "the best scientific and commercial data available." Through consultation with either FWS or NMFS, federal agencies must ensure that their actions are "not likely to jeopardize the continued existence" of any endangered or threatened species, nor to adversely modify critical habitat. This is referred to as a Section 7 consultation . "Action" includes any activity authorized, funded, or carried out by a federal agency, including permits and licenses. Consultation is usually begun at the request of the action agency but may be initiated at the request of an FWS Regional Director or NMFS's Assistant Administrator for Fisheries. Where a federal action is dictated by statute, a Section 7 consultation is not required. If the appropriate Secretary finds that an action would neither jeopardize a species nor adversely modify critical habitat, the Secretary issues a biological opinion (BiOp) to that effect, and the agency is provided with a written incidental take statement, specifying the terms and conditions under which the federal action may proceed in order to avoid jeopardy or adverse modification of critical habitat. Alternatively, if the proposed action is judged to jeopardize listed species or adversely modify critical habitat, the Secretary must suggest any reasonable and prudent alternatives that would avoid harm to the species. The ESA does not expressly state that the BiOp is to be based on the "best scientific and commercial data available," but this arguably is implied and is expressly required under the implementing regulations, which require that the consulting agency provide "the best scientific and commercial data available or which can be obtained during the consultation." Such information is to be the basis of the BiOp, and the BiOp is to include a summary of the information on which the opinion is based. The great majority of consultations result in "no jeopardy" opinions, and nearly all of the rest find that the project has reasonable and prudent alternatives, which will permit it to go forward. The relevant Secretary generally is to complete consultation within 90 days for a wholly federal action, unless the Secretary and the federal agency mutually agree to a longer period (up to 150 days) and reasons are given for the delay. A consultation involving a nonfederal party is to be completed within the time agreed to by the Secretary, the federal agency involved, and the applicant concerned. In practice, formal consultation may take a year or more. If no reasonable and prudent alternatives are feasible, then the agency proposing the action must (1) forego the action, (2) risk incurring penalties under the ESA, or (3) obtain a formal exemption from the penalties of the ESA as set out below. If the jeopardy that is expected to result from a proposed agency action cannot be avoided and the agency proposing the action nonetheless wants to go ahead with the action, the agency (or the affected governor(s) or license applicant(s)) may apply for an exemption to allow the action to go forward. Exemptions are available only for actions (e.g., water withdrawals), not for species (e.g., Delta smelt). A high-level Endangered Species Committee (ESC) of six specified federal officials and a representative of each affected state (often called the "God Squad") decides whether to allow the action to proceed despite future harm to a species; at least five votes are required to pass an exemption. The six federal officials are the Secretaries of the Interior (chair), Agriculture, and the Army; the Chair of the Council of Economic Advisors; and the Administrators of the National Oceanic and Atmospheric Administration and of the Environmental Protection Agency. The law includes extensive rules and deadlines to be followed in applying for such an exemption, a full administrative hearing, and some stringent rules for the ESC in deciding whether to grant an exemption. The ESC must grant an exemption if the Secretary of Defense determines that an exemption is necessary for national security. In addition, and under specified circumstances, the President may determine whether to exempt a project for the repair or replacement of facilities in presidentially declared disaster areas. (A separate discussion of the six times when the exemption process has been invoked is provided in the Appendix .) To be eligible for an exemption, the federal agency concerned (and any nonfederal exemption applicant) must have carried out the consultation processes required under Section 7 of the ESA in good faith. Under Section 7(g), the agency also must have made a reasonable and responsible effort to develop and fairly consider modifications or reasonable and prudent alternatives to the proposed action that would not jeopardize the continued existence of any endangered or threatened species or destroy or adversely modify critical habitat of a species. The agency must also have conducted required biological assessments. In addition, to the extent determinable within the time provided, the agency must have refrained from making any irreversible or irretrievable commitment of resources. (Such commitments are those that would foreclose the formulation or implementation of reasonable and prudent alternatives that would avoid jeopardizing the species and/or adversely modifying its habitat.) These qualifying requirements were put in place to ensure that the exemption process is meaningful and that consideration of the issues would not be preempted by actions already taken. Additional requirements for an application are contained in the relevant regulations. The ESC shall grant an exemption for the project or activity if, based on the evidence, the ESC determines that (i) there are no reasonable and prudent alternatives to the agency action; (ii) the benefits of such action clearly outweigh the benefits of alternative courses of action consistent with conserving the species or its critical habitat, and such action is in the public interest; (iii) the action is of regional or national significance; and (iv) neither the federal agency concerned nor the exemption applicant made any irreversible or irretrievable commitment of resources prohibited by subsection (d) of this section [commitments that jeopardize species or critical habitat]. In addition, the ESA specifies particular instances when special provisions will apply to the granting of an exemption. These provisions concern international treaty obligations, national security, and presidentially declared disasters. The ESA does not have a general provision that allows the granting of an exemption in other emergency conditions. As outlined above, the exemption process is a complex affair for the applicant, and even without extensions, could take 280 days. Since a decision to exempt an action would, by definition, jeopardize the continued existence of a species, some find a rigorous process to be appropriate. But even were the process simple, any potential exemption applicant would face these challenges: The applicant must fund any required mitigation measures; the funding obligation lasts for the life of the action—potentially forever depending on the nature of the action. Because the exemption applies to the action and not to the species, FWS or NMFS must continue to attempt to recover the species. Consequently, the burden of conservation and recovery may fall that much more heavily elsewhere. A governor, trying to balance the interests of an entire state, might find this a particularly difficult obstacle. If conservation of a listed species is only one of various statutory obligations under federal or state laws, then an exemption from the ESA for the action may not be sufficient to allow an action to go forward, since those other statutory obligations may still be required. Many parties to a dispute may be reluctant to appear to side publicly with the extinction of a species. Moreover, if the increased risk of extinction provides only modest advancement for the action, the rewards of a successful exemption application may not seem worth the effort. As a practical matter, the consultation process itself offers federal agencies many opportunities to modify their actions to avoid jeopardizing species or adversely modifying their designated critical habitats yet still proceed with their actions. The well-known implications of an ESA conflict prompt agencies to consider the ESA consequences at a very early stage in their actions and to avoid conflict, and specifically to avoid the need for an exemption. For actions by private parties that might take a listed species, but without any federal nexus such as a loan or permit, the Secretary may issue permits to allow "incidental take" of species for otherwise lawful actions. The applicant for an incidental take permit (ITP) must submit a habitat conservation plan (HCP) that shows the likely impact, the steps to minimize and mitigate the impact, the funding for the mitigation, the alternatives that were considered and rejected, and any other measures that the Secretary may require. In the 1990s, the use of this section was greatly expanded, and an agency handbook provides for streamlined procedures for activities with minimal impacts. Other provisions specify certain exemptions for raptors; regulate subsistence activities by Alaskan Natives; prohibit interstate transport and sale of listed species and parts (e.g., ivory); control trade in parts or products of an endangered species that were owned before the law went into effect; and specify rules for establishing experimental populations. (Provisions of the ESA referring to international activities are discussed below.) The ESA enumerates various prohibited acts, including taking endangered species; possessing, selling, or transporting any unlawfully taken endangered species; and violating any regulation promulgated by FWS or NMFS pertaining to any endangered or threatened species. As noted above, in the absence of a special rule for a species listed as threatened, agency rules provide that threatened species are subject to essentially the same protections and prohibitions as endangered species. Attempting to commit, soliciting another to commit, or causing to be committed any prohibited act is also a violation of the ESA. The ESA's prohibitions apply broadly to any person subject to the jurisdiction of the United States. Sections 9 and 10 of the ESA provide exceptions when the prohibitions will not apply, including incidental take permits, as discussed above. Section 11 of the ESA also provides that no civil penalties will be imposed on persons who can show that they committed an ESA violation based on a good-faith belief that they were protecting themselves or another person from bodily harm from any endangered or threatened species. Any person who violates any provision of the ESA or any regulation or permit issued pursuant to the ESA may be subject to civil penalties for each violation. Knowing violators and persons engaged in business as importers or exporters of fish, wildlife, or plants are subject to higher fines. Knowing violations of most of the ESA's statutory provisions may also be criminal violations. The ESA contains a number of provisions relating to enforcement. Any person may bring a lawsuit in federal district court to enjoin anyone, including governmental entities, who the person alleges to be in violation of any provision of the ESA or its regulations or to compel the Secretary to perform a nondiscretionary duty under the ESA's listing-related provisions in Section 4. The person generally must provide written notice of intent to sue at least 60 days prior to bringing the action. The ESA also expressly provides that the court may award litigation costs and attorneys' fees to any party whenever the court determines such an award to be appropriate. The citizen suit provisions of the ESA have been a driving force in the ESA's history and often have been used to force agencies to devote greater effort toward conserving the species in question. At least one study suggests that citizen groups drive listings of species that may be at greater risk than those proposed by FWS; the same article presented data to support the thesis that citizen proposals for listings are more likely to concern species in conflict with development. ESA citizen suits seeking to list species, or to challenge delays in listing decisions, amount to a significant number of lawsuits against FWS and NMFS. In addition to providing for listing and protecting species, the ESA is the implementing legislation for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on Nature Protection and Wildlife Preservation in the Western Hemisphere (the Western Hemisphere Convention) for the United States. CITES parallels the structure of ESA by dividing its listed species into groups according to the estimated risk of extinction, but uses three major categories, rather than two. In contrast to the ESA, CITES focuses exclusively on trade, and does not consider or attempt to control habitat loss. The ESA makes violations of CITES violations of U.S. law if committed within the jurisdiction of the United States. Through the Western Hemisphere Convention, the United States committed to establishing various categories of nature reserves, controlling international wildlife trade with other signatories, and protecting wildlife more generally. To some extent, the convention's goals have been subsumed under those of the ESA and other international treaties, particularly with respect to wildlife conservation. The following are the major international provisions of the ESA. The ESA designates the Secretary of the Interior as the Endangered Species Scientific Authority (ESSA) specified under CITES. As the ESSA, the Secretary must determine that the United States' international trade of living or dead organisms, or their products, will not harm the species in question. The Secretary has authority to enforce these determinations; this authority is exercised through FWS. The Secretary is required to base export determinations upon "the best available biological information," although population estimates are not required. Certain other ESSA responsibilities are also spelled out in CITES. The Secretary of the Interior is also named as the Management Authority for the United States under CITES. The Management Authority must assure that specimens are exported legally; that imported specimens left the country of origin legally; and that live specimens are shipped under suitable conditions. Certain other Management Authority responsibilities are also spelled out in CITES. In general, the ESA prohibits any person subject to the jurisdiction of the United States from importing into, or exporting from, the United States any listed species. The ESA sets forth exceptions under which the Secretary may permit such import or export for scientific purposes or to enhance the propagation or survival of the affected species, and certain other exceptions. To enhance enforcement of the trade-related provisions of the ESA, the ESA requires importers and exporters of fish or wildlife (other than most shellfish and fishery products) to obtain permission from the Secretary to engage in such business; to keep records and allow inspections; and to use certain ports designated by the Secretary, unless the Secretary deems it appropriate and consistent with the ESA to permit importation or exportation elsewhere. In three instances, an Endangered Species Committee (ESC) reached a decision on an application for an exemption: Grayrocks Dam. The Platte River is a major stopover site on the migration path of whooping cranes, listed under the ESA as an endangered species. FWS determined that the construction of the Grayrocks Dam and Reservoir in Wyoming, along with existing projects in the Platte River Basin, would jeopardize the downstream habitat of whooping cranes. The ESC voted (7-0) to grant an exemption for Grayrocks Dam and Reservoir on January 23, 1979, conditioned on specified mitigation measures that included maintenance and enhancement of critical whooping crane habitat on the Platte River, as well as a permanent, irrevocable trust fund to pay for these activities. A previous enactment by Congress would have exempted the project, if the ESC had not reached a decision within a certain time. Tellico Dam. The Tellico Dam on the Little Tennessee River was to serve multiple purposes. It was vigorously opposed by several sectors, including local landowners and Indian tribes. After the snail darter (a fish) was listed as endangered, litigation was filed to stop the construction of the dam, resulting in the landmark Supreme Court case TVA v. Hill . The decision clarified the broad reach of the ESA, and its relationship to the question of ratification of public works projects through appropriations measures. The decision was quickly followed by congressional passage of P.L. 95-632 , which provided for an ESC process. The measure also gave an automatic exemption to the dam if the ESC did not reach a decision within a specified time. Directed to take economic implications into account, the ESC denied an exemption for Tellico (on a 7-0 vote), but in P.L. 96-69 , Congress directed that the dam be completed, notwithstanding any other provision of law. Subsequently, additional snail darters were found in a few other locations, and the snail darter was reclassified as threatened. Bureau of Land Management Timber Sales. The Bureau of Land Management, an agency in DOI, sought an exemption for 44 Oregon timber sales in the habitat of the threatened northern spotted owl. In 1992, the ESC voted (5-2) to grant an exemption for 13 of the sales. Controversy over the sales and the processes within the department continued, and the 13 timber sales were subsequently withdrawn in the Clinton Administration. In three other instances, there were applications for exemptions, but no ESC decisions: Pittston Company Refinery. The Pittston Company applied for an exemption to build a refinery in Eastport, ME. Following jeopardy opinions based on probable effects on threatened bald eagles and endangered right and humpback whales, the company applied for an exemption, but further action on this application appears to have been discontinued in 1982. Consolidated Grain and Barge Company Docking Area. This company sought to build a docking area for barges at Mound City, IL, on the Ohio River, an area that was habitat for an endangered mussel. Following a jeopardy opinion, and a denial of permits by the Army Corps of Engineers, the company applied for an exemption, but withdrew the application in 1986. Suwanee River Authority. The consulting engineer of the Suwanee River Authority applied for an exemption for a project to dredge Alligator Pass in Suwanee Sound, Florida, part of the habitat for the endangered manatee. The project had been denied a permit by the Army Corps of Engineers. The engineer apparently lacked the authority to apply on behalf of the Authority, which in 1986 refused to ratify his actions and withdrew the application. Although the engineer attempted to continue the application, the withdrawal was effective.

Summary: The Endangered Species Act (ESA; P.L. 93-205, 87 Stat. 884. 16 U.S.C. §§1531-1544) has a stated purpose of conserving species identified as endangered or threatened with extinction and conserving ecosystems on which these species depend. The ESA is perennially controversial because the protections provided can make it the visible policy focal point for underlying situations involving the allocation of scarce or diminishing lands or resources, especially in instances where societal values may be changing or traditional land use patterns are affected. As a result, the act often becomes controversial even where a particular species is not the focus of a controversy but a symptom of it. In response to past controversies, Congress has repeatedly considered minor amendments and major changes to the ESA. The major features of the ESA and related controversies are briefly summarized as follows: ESA retains its authorities even though its authorization for funding expired in 1992, and funds may be and have been appropriated in the absence of a current authorization. ESA prohibitions and penalties remain in effect regardless of appropriations. ESA's principal parts are the listing and protection of species, designation of critical habitat and avoidance of its destruction, and consultation by federal agencies regarding actions that may harm listed species. Dwindling species are listed as either endangered or threatened according to assessments of the risk of their extinction. Once a species is listed, legal tools are available to aid its recovery and to protect its habitat. ESA has broad provisions for citizen suits to enforce the act, and lawsuits have played a major role in enforcement and interpretation of many, or perhaps most, of the act's provisions. ESA provides for exemptions from the act for agency projects, but the provisions are little used for a variety of reasons. The act is administered primarily by the Fish and Wildlife Service for terrestrial and freshwater and by the National Marine Fisheries Service for most marine and anadromous species. ESA is the implementing legislation for U.S. participation in the Convention on International Trade in Endangered Species (CITES).