Improving the Protection of Species Endangered in the United States by Revising the Distinct Population Segment Policy

Allison Westfahl Kong

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This editorial summarizes my forthcoming Note, 85 N.Y.U. L. REV. 358 (2010), wherein I argue that the Distinct Population Segment (DPS) Policy1 should be revised to allow the listing of species that are endangered solely within the United States.

Someday in the future, Americans may be distressed to discover that the last remaining domestic population of the American bald eagle, the symbol of their country, is about to become extinct and that the Fish and Wildlife Service (FWS) refuses to protect the population, despite a mandate to protect endangered species under the Endangered Species Act (ESA).2 The agency argues that due to existing policies and court decisions, it cannot protect domestic populations of endangered species, even cherished ones, when the species is thriving in another country and other certain demanding conditions are not met. If this scenario seems far fetched, a somewhat parallel situation is now unfolding. When the National Marine Fisheries Service (NMFS) decided to protect an endangered population of the Cook Inlet beluga whale, the State of Alaska announced it would challenge the decision in court, arguing that, under current policy, the population was insufficiently “significant” to the species as a whole to warrant protection. If courts agree, which is a possibility because of ambiguities in the relevant policies and court decisions, Alaskans could be deprived of a beautiful marine species inhabiting their coastal waters.

Whether Alaska will proceed with its lawsuit is uncertain—especially after the resignation of Governor Palinbut the threatened lawsuit demonstrates the increasing difficulty of  listing U.S. populations of species as endangered when these species are abundant outside the United States. Under current policy, species within the United States are denied protection simply because they are not a significant portion of the species’ global population. This Note argues that this policy should be revised to permit the listing of species that are endangered solely within the U.S.

Rationale for Protecting Species That Are Solely Endangered Within the United States

Responding to an unnatural rate of extinction among species, Congress passed the ESA in 1973. The main rationale for protecting endangered species is that species are valuable—or may turn out to be valuable—to humans in several ways. Many life-saving medical treatments have been developed from studying non-human species, and the existence of diverse species safeguards our food supply from pests.

There are also reasons to protect domestic populations of species even when they are not at risk of global extinction. First, protecting domestic populations of species serves the goal of international protection, ensuring that the species exists somewhere in the world. The current DPS Policy does not distinguish between a domestic population found in only one other country and a population that is abundant throughout the globe. However, a species is more likely to become extinct if there are only two populations of the species—one in the United States and one elsewhere—as opposed to several populations in multiple countries. Efforts to preserve the domestic population would be prudent in the first case, but perhaps unnecessary in the second. Furthermore, if the United States allows domestic populations of species to become extinct, we must rely on other countries to protect those species, and those countries may not adopt measures to protect their populations. Even when countries value species protection, if a species exists in many countries, no single country may take the initiative to protect that species, resulting in its global extinction.

Second, Americans may value having species located within the United States regardless of global populations. Even if it were hypothetically guaranteed that a species would never become extinct in another country, we may still want the species to continue existing within our borders. Many species have special cultural significance to the American people—e.g., the American bald eagle—­and species with aesthetic value increase tourism in certain regions—­e.g., the Cook Inlet beluga population attracts tourists to Alaska.

The Flaw in Current Policy: Domestic Populations of Species Do Not Receive Proper Protection

Since its passage, the ESA has been the United States’ primary mechanism to protect endangered species—both here and around the world—by requiring the listing of endangered and threatened species and mandating appropriate protective actions. Two federal agencies implement most provisions of the ESA: the FWS and the NMFS.

The ESA defines “endangered species” to include “any species which is in danger of extinction throughout all or a significant portion of its range.”3 The current definition of “species” includes subspecies as well as “distinct population segment[s] of any species of vertebrate fish or wildlife which interbreed[] when mature.”4 Because “distinct population segment” is neither a scientific term nor defined in the ESA, considerable controversy surrounded the listing of DPSs after Congress added this language to the ESA in 1978. In 1979, the Government Accountability Office expressed concern about DPS designations, arguing that FWS would abuse its power and list tiny populations of species that were insignificant to the species as a whole. Amendments to the ESA in 1979 based on these concerns did not eliminate DPSs, but the Senate Committee on Environment and Public Works responded to such concerns by suggesting that FWS list DPSs “sparingly.”5

In 1996, nearly two decades after the ESA first allowed the listing of DPSs, FWS and NMFS adopted the DPS Policy to establish three requirements for a population segment to be listed as threatened or endangered:

1. Discreteness of the population segment in relation to the remainder of the species to which it belongs;

2. The significance of the population segment to the species to which it belongs; and

3. The population segment’s conservation status in relation to the Act’s sta6

If the agency finds that discreteness is satisfied, it must decide whether the population segment is “significant” by considering four non-exclusive factors:

1. Persistence of the discrete population segment in an ecological setting unusual or unique for the taxon;

2. Evidence that loss of the discrete population segment would result in a significant gap in the range of a taxon;

3. Evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range; or

4. Evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.7

While the DPS Policy represented a sincere effort to resolve  ambiguities in the term “distinct population segment,” it was doomed to provoke litigation due to this paradox: Despite congressional desire to designate DPSs solely based on “biological evidence,”8 the fact that “distinct population segment” is not a scientific term means that whether one exists cannot be established with scientific evidence.

Two recent court decisions—National Ass’n of Home Builders v. Norton9 and Northwest Ecosystem Alliance v. U.S. Fish & Wildlife Service10—have interpreted the DPS Policy in ways that undermine efforts to protect domestic populations of species. Home Builders directly addressed the issue of whether domestic populations of species should be protected if the species is abundant in another country, and the court made such protection more difficult. After FWS listed the western pygmy-owl population in Arizona as an endangered DPS, the plaintiff challenged the listing, arguing that it violated the DPS Policy because the population of pygmy-owls was not “significant.” Although FWS found that delisting the Arizona pygmy-owl would “extirpate the western pygmy-owl from the United States,”11 the court ruled that a population’s significance to the United States could not be used to satisfy the significance requirement under the DPS Policy.

While the plaintiff in Home Builders did not challenge the DPS Policy itself, other cases have addressed the policy’s legality, including Northwest Ecosystem Alliance. In that case, the plaintiff argued that the “requirement that a population be significant to its taxon [was] unlawfully restrictive.”12 The court rejected this argument, finding that FWS’s consideration of a population’s significance to the overall species is not contrary to the ESA. Both decisions have made it more difficult to protect domestic populations under current DPS Policy. However, as argued below, FWS and NMFS have the authority to change the DPS Policy to enhance the protection of domestic populations since the ESA does not forbid protecting species that are solely endangered in the United States.

A Proposed Solution: Revising the Current DPS Policy

There are two problems with the current DPS Policy. First, it does not adequately meet the goal of international protection because it fails to protect domestic populations of species that may become extinct elsewhere. Second, it does not meet the goal of domestic protection because it fails to protect species that we value having within U.S. borders. To solve these problems, I argue that FWS and NMFS should revise the significance prong of the DPS Policy to allow the listing of DPSs endangered solely within the United States in certain circumstances.

Specifically, I propose that when a population segment is significant to the U.S. population but not the overall range of the taxon, FWS and NMFS should consider (1) whether the DPS should be protected because of potential risks to foreign populations of the species, and (2) whether the DPS should be protected because Americans value having the species within U.S. borders. To determine whether the first prong is satisfied, agencies should weigh and balance three factors: the relative abundance of the species in other nations, the conservation efforts of those nations, and the extent of known environmental risks to global populations that could cause the species’s extinction. For the second prong, to determine whether a species is significant to the American people, FWS and NMFS should seek tangible evidence of the species’s importance, including the species’s appearance in governmental iconography, tourism revenue generated by the species’s presence, and the extent to which there have been local movements to preserve the species. If either the first or second prong is met, FWS or NMFS should list the population segment, provided that it meets the other two requirements of the DPS Policy—discreteness and endangered or threatened status.

With my proposal in place, FWS could unambiguously justify its listing of the Cook Inlet beluga, and Alaska would find it difficult to mount a legal challenge. Regardless of whether the Cook Inlet beluga is significant to the taxon as a whole, the population segment would be protected based on my proposal’s second prong because, while the beluga is not an official state animal, there have been local efforts to preserve it and it is a tourist attraction that generates significant revenue. Thus, species like the beluga that are culturally significant and important to local economies would be protected under my proposal.

One concern about my proposal might be that a policy making it easier to list domestic populations of species might lead to excessive restraints on private enterprise—the issue behind the Home Builders case—or require vast increases in government expenditures to protect species. However, since the conditions required by my proposal are uncommon, it is unlikely to significantly increase the number of protected domestic populations. Others might consider my proposal too timid because it might preclude protection of vulnerable domestic populations when foreign populations are insufficiently threatened or because the species is not charismatic. Still, because an agency’s decision not to list a population can be challenged at any time, one can be reasonably confident that a population meriting protection will eventually be listed.

The remaining question is whether this proposed solution is consistent with the ESA. I argue that the ESA’s text and legislative history suggest that Congress intended neither to mandate nor forbid the protection of species which are endangered solely within the United States. Thus, while the ESA does not necessitate changing the DPS Policy, the delegated agencies would have the authority to amend the DPS Policy to enhance domestic protection.

The legislative history suggests that Congress thought the ESA could be used to protect domestic populations. For example, the committee report accompanying the original 1973 House bill explains that the ESA could be used to protect a species endangered within the United States even if it was abundant in Canada or Mexico. Even after the definition of species was narrowed in 1978, the Senate Committee on Environment and Public Works expressed that “the U.S. population of an animal should not necessarily be permitted to become extinct simply because the animal is more abundant elsewhere in the world.”13

The text of the ESA also suggests that it could be used to protect species that are endangered solely in the United States. For example, the Findings section reveals a purely domestic purpose: “[T]hese species . . . are of esthetic, . . . recreational, and scientific value to the Nation and its people.”14 Thus, the ESA is concerned not only with protecting species for scientific and biological reasons, but also with protecting species that have “esthetic” and “recreational” value. This demonstrates a commitment to allowing Americans to take advantage of the recreational and scientific benefits that endangered species provide, suggesting that protection of domestic species is important under the ESA.

Since the ESA does not forbid protecting species that are endangered solely within the United States, and since the text suggests that it may be important to protect species domestically, FWS and NMFS have the authority to change the DPS Policy to protect endangered domestic populations.


While the DPS Policy is not clearly contrary to the ESA—which is primarily concerned with ensuring that species exist somewhere in the world, not specifically in the United States—there are compelling reasons to protect species that are endangered solely within our borders. Since the loss of a species is an irreversible harm, domestic populations of species may merit protection if there are strong indications that foreign populations may face extinction in the future. In addition, some species hold cultural, educational, and aesthetic significance for Americans and should be protected regardless of how abundant the species are abroad. To enhance species protection both internationally and domestically, the DPS Policy should be revised to allow government agencies to preserve domestic populations of species in certain instances. Then, Americans would not have to worry about someday losing some of their most cherished animals.


Copyright © 2010 New York University Law Review.

Allison L. Westfahl Kong received her JD from New York University Law Review in 2010.

This Editorial is an abbreviated version of Allison L. Westfahl Kong, Note, Improving the Protection of Species Endangered in the United States by Revising the Distinct Population Segment Policy, 85 N.Y.U. L. Rev. 358 (2010). A previous version of this Note was the winner of the second annual student writing  competition of the New York State Bar Association’s Committee on Animals and the Law.

  1. Policy Regarding the Recognition of Distinct Vertebrate Population Segments Under the Endangered Species Act, 61 Fed. Reg. 4722 (Feb. 7, 1996) {hereinafter DPS Policy}.
  2. 16 U.S.C. § 1532 (2006).
  3. 16 U.S.C. § 1532(6) (2006).
  4. Endangered Species Act Amendments of 1978, Pub. L. No. 95-632, § 5, 95 Stat. 3751, 3752 (codified as amended at 16 U.S.C. § 1532(16) (2006)) (emphasis added).
  5. S. REP. NO. 96-151, at 7 (1979) (“{T}he committee is aware of the great potential for abuse of this authority and expects the FWS to use the ability to list populations sparingly and only when the biological evidence indicates that such action is warranted.”).
  6. DPS Policy, supra note 1, at 4725.
  7. Id.
  8. See S. REP. NO. 96-151, at 7 (1979) (noting that committee “expects” FWS to list DPSs “sparingly and only when the biological evidence indicates that such action is warranted”).
  9. 340 F.3d 835 (9th Cir. 2003).
  10. 475 F.3d 1136 (9th Cir. 2007).
  11. Final Rule To Remove the Arizona Distinct Population Segment of the Cactus Ferruginous Pygmy-Owl (Glaucidium brasilianum cactorum) from the Federal List of Endangered and Threatened Wildlife, 71 Fed. Reg. 19,452, 19,457 (Apr. 14, 2006) (citing Determination of Endangered Status for the Cactus Ferruginous Pygmy-Owl in Arizona, 62 Fed. Reg. 10,730, 10,734 (Mar. 10, 1997)).
  12. Nw. Ecosystem Alliance, 475 F.3d at 1140.
  13. S. REP. NO. 96-151, at 7 (1979).
  14. 16 U.S.C. § 1531 (2006).

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