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Ninth Circuit Defers to Services’ Interpretation of “Distinct Population Segments” Under the ESA

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February 22, 2007

Earlier this month, the Ninth Circuit Court of Appeals addressed an issue at the heart of listing decisions under the Endangered Species Act (ESA): the meaning of the term “species.” In Northwest Ecosystem Alliance v. U.S. Fish and Wildlife Service (Alliance v. FWS), the Ninth Circuit deferred to the federal wildlife services’ policy interpretation of the term “distinct population segment” (DPS) within the ESA’s definition of “species.” The Court also upheld the U.S. Fish and Wildlife Service’s (FWS) application of that policy to a particular subspecies in Washington State.[i] The Ninth Circuit is the first appellate court to explicitly consider a facial challenge to the services’ interpretation of the term “DPS.”

Background: The DPS Analysis

The ESA defines the term “species” to include “any subspecies of fish or wildlife or plants, and any [DPS] of any species of vertebrate fish or wildlife which interbreeds when mature.”[ii] Under this definition, “a population of wildlife that does not constitute a taxonomic species may nevertheless qualify for listing as a DPS.”[iii] The term “DPS” is neither defined in the ESA nor commonly used in scientific discourse. In fact, it has no accepted scientific meaning.[iv] To fill this gap, the FWS and the National Marine Fisheries Service (NMFS) adopted a policy statement (DPS Policy) “to guide their evaluation of whether a population group should be treated as a DPS.”[v] The Services published a draft of the policy on December 21, 1994, and invited public comment. [vi] After considering comments, the Services adopted the policy as it had been issued in draft form.[vii]

The DPS Policy sets forth two factors for the Services’ consideration: the “[d]iscreteness of the [DPS] in relation to the remainder of the species to belongs,” and the “significance of the population segment to the species to which it belongs.”[viii] Discreteness is satisfied if a population segment is “‘separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors,’ or if a population’s boundaries are marked by international borders.”[ix] The Services analyze “significance” under four non-exclusive factors: (1) whether the population persists in a unique or unusual ecological setting; (2) whether the loss of the population would cause a “significant gap” in the taxon’s range; (3) whether the population is the only surviving natural occurrence of a taxon; and (4) whether the population’s genetic characteristics are “markedly” different from the rest of the taxon.[x] A population qualifies as a DPS only if the appropriate Service decides it is both discrete and significant. If a population qualifies as a DPS, the Service then decides whether the DPS is endangered or threatened.[xi] 

Multiple district courts and a handful of appellate courts have considered as-applied challenges to various DPS decisions.[xii] For example, the Ninth Circuit considered a petition to list a goshawk population as an endangered DPS in Center for Biological Diversity v. Badgley, and deferred to the FWS’ decision not to list the species.[xiii] In National Association of Home Builders v. Norton, the Ninth Circuit determined that the FWS did not properly apply the DPS Policy in listing a certain population of pygmy owls.[xiv] th

In 2003, Judge Lasnik of the District Court for the Western District of Washington addressed the validity of the DPS Policy itself in Center for Biological Diversity v. Lohn, a case concerning the Eastern North Pacific Southern Resident Killer Whales.[xv] Judge Lasnik concluded that the DPS Policy was not contrary to congressional intent, and that it constituted a reasonable interpretation of an ambiguous statutory term.[xvi] In Maine v. Norton, the District Court for the District of Maine considered the propriety of the Services’ determination that a Gulf of Maine Atlantic salmon population was a DPS, and did not disturb the Services’ listing decision.[xvii] The Maine v. Norton court also concluded that the DPS Policy is “a reasonable interpretation of ambiguous statutory language.”[xviii] Before Alliance v. FWS, however, no appellate court had explicitly addressed the validity of the DPS Policy on its face.[xix]

Procedural History of the Ninth Circuit’s Opinion in Alliance v. FWS

The opinion in Alliance v. FWS specifically concerns one of three subspecies of the western gray squirrel (Sciurus griseus griseus), the largest native tree squirrel in the Pacific Northwest.[xx] The western gray squirrel is fairly common in California, legally hunted in Oregon, and classified as “protected” under state law in Nevada.[xxi] Washington law also protects the western gray squirrel populations.[xxii] Due in part to their historic separation from other subspecies by the Columbia River, the Washington subspecies has been reduced to three geographically isolated populations over the last three decades.[xxiii] In 1998 and 1999, surveyors detected only six western gray squirrels of the so‑called “Puget Trough population.” The other Washington populations showed significantly higher numbers, albeit at densities lower than historic levels.[xxiv] In January 2001, Plaintiffs (collectively, the Alliance) petitioned the FWS to list Washington’s western gray squirrel populations under the ESA. The FWS denied the petition, concluding that the population was not significant to the taxon to which it belongs under the DPS Policy.[xxv] The Alliance then sued the FWS, contending that its decision was arbitrary and capricious. The district court granted summary judgment for the FWS.[xxvi]

The Ninth Circuit’s Opinion in Alliance v. FWS

The appeal presented two issues: “(1) whether the [FWS’] construction of the term ‘[DPS]’ is entitled to Chevron deference, and if so, whether the [FWS’] construction is reasonable; and (2) whether the [FWS’] denial of the petition was arbitrary and capricious.”[xxvii] The Alliance argued that “the DPS Policy’s requirement that a population be significant to its taxon is unlawfully restrictive. The Alliance d[id] not seek to invalidate the DPS Policy on its face, but only as applied [to the Washington population of western gray squirrel].”[xxviii] The Ninth Circuit elected to take a broader view, explaining:

We may nevertheless consider the general validity of the element of the DPS Policy – i.e., the significance requirement – that was used by the [FWS] to deny the Washington gray squirrel a listing as an endangered DPS. We may not, however, evaluate elements of the DPS Policy that were not applied against the Alliance. We note that the [FWS] does not argue on appeal that the validity of the significance requirement cannot be evaluated in an as-applied suit. We also note that, before the district court, the [FWS] did not challenge the Alliance’s first claim for relief. It is this claim, that the [FWS] ‘had a nondiscretionary duty to list the Washington populations of the western gray squirrel under the ESA upon determining they are imperiled [DPSs],’ that objects to the existence of the significance requirement rather than merely its application to the Washington gray squirrels.[xxix]

The Validity of the DPS Policy

Under Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc.,[xxx] a court reviewing an administrative interpretation of a statute must first decide whether Congress has spoken clearly on the issue. If the statute is clear, the court “must give effect to the unambiguously expressed intent of Congress,” regardless of the agency’s opinion.[xxxi] If the statute is ambiguous, then, according to the Ninth Circuit, a court “must determine how much deference to give to the administrative interpretation,” depending on the statute and agency action at issue.[xxxii] Chevron deference applies “when it appears that Congress delegated authority to the agency generally to make rules carrying the force of law, and that the agency interpretation claiming deference was promulgated in the exercise of that authority.”[xxxiii] Although the Alliance did not seek to invalidate the DPS Policy on its face, nor did it argue that the Policy is not entitled to deference,[xxxiv] the Court still addressed the issue, concluding that the DPS Policy is entitled to deference under Chevron.[xxxv] In reaching this conclusion, the Court pointed to the “procedural rigors” to which the Services applied the DPS Policy, “the express congressional command to the Service[s] to develop guidelines,” and the treatment of the DPS Policy – by both the Services and parties presenting listing petitions – as legally binding. The Court found that “these factors distinguish the DPS Policy from garden-variety policy statements that do not enjoy Chevron status.”[xxxvi]

The Challenge to the DPS Policy, as Applied to the Listing Decision

Addressing the second factor in the DPS analysis (the “significance” inquiry), the Court noted that the FWS’ discussion of whether the loss of the population would cause a “significant gap” in the taxon’s range “is not a paragon of clarity.”[xxxvii] Still, the Court rejected the following arguments proffered by the Alliance: (1) that the DPS Policy contradicts the alleged plain meaning of the statute; (2) that the FWS’ finding that certain subpopulations do not constitute unique ecological settings for the taxon within the meaning of the DPS Policy was arbitrary and capricious; (3) that the FWS inappropriately found that a hypothetical loss of the entire Washington population would not cause a significant gap in the range of the taxon; and (4) that the FWS failed to acknowledge marked genetic differences between subpopulations of the taxon.[xxxviii] The Court deferred to the FWS’ decisions that: (1) the relevant population does not persist in a unique ecological setting; (2) loss of the population would not result in a significant gap in the range of taxon; and (3) the population is not markedly different genetically from other populations of the species.[xxxix] The Court concluded that the FWS’ decision not to designate Washington’s western gray squirrel population as a DPS, therefore, was not arbitrary and capricious, and was entitled to deference.


Narrowly construed, the Ninth Circuit’s opinion in Alliance v. FWS means that Washington’s western gray squirrel populations are not protected by the ESA and, as a consequence, property owners and other members of Washington’s regulated community will not be subject to restrictions necessitated by federal protection of the state’s gray squirrels. The subspecies and its nest trees, however, remain protected under state law. The longer term significance of the Ninth Circuit’s opinion, however, may lie less in any immediate practical impact involving the gray squirrel than in its long term consequence for future listing decisions. The Court’s deference to the Services’ controversial interpretation of the word “significance” in the phrase “DPS” allows the Services to continue making listing decisions below the species level as they have for the past decade. Previous Senate committees and the General Accounting Office have voiced concerns that inclusion of the phrase “DPS” in the definition of the term “species” could result in an unrestrained “proliferation of endangered species listings.”[xl] By upholding the Services’ four-factor “significance” test under the DPS Policy, the Ninth Circuit has arguably furthered the U.S. Senate’s expectation, first voiced 18 years ago: that the Services would “use the ability to list populations sparingly and only when the biological evidence indicates that such action is warranted.”[xli]


[i] No. 04-35860, --- F.3d ---, 2007 WL 286581 (9th Cir. Feb. 2, 2007).

[ii] 16 U.S.C. § 1532(16).

[iii] Alliance v. FWS, 2007 WL 286581, at *1.

[iv] Nat’l Ass’n of Home Builders v. Norton, 340 F.3d 835, 842 n.8 (9th Cir. 2003) (quoting Policy Regarding the Recognition of Distinct Vertebrate Population Segments Under the Endangered Species Act, 61 Fed. Reg. 4722, 4722 (Feb. 7, 1996) (DPS Policy) (internal quotations omitted); Northwest Ecosystem Alliance v. U.S. Fish and Wildlife Service (NWEA v. FWS I), No. 03-1505, Not Reported in F.Supp.2d, 2004 WL 792805, at *1 (D. Or. March 16, 2004) (citing Ctr. for Biological Diversity v. Lohn, 296 F.Supp.2d 1223, 1234 (W.D. Wash. 2003)).

[v] Alliance v. FWS, 2007 WL 286581, at *1 (citing DPS Policy). The DPS Policy also describes another conservation unit, referred to as both an “evolutionarily significant unit” and an “evolutionary significant unit” (“ESU”). Under the DPS Policy, “a stock of Pacific Salmon is considered a DPS if it represents an [ESU] of a biological species,” in that it is “substantially reproductively isolated from other conspecific population units,” and it “represent[s] an important component in the evolutionary legacy of the species.” DPS Policy at 4722. The Services decided that their interpretation of the phrase “ESU” is consistent with the DPS Policy. Id. Scholars, lawyers, environmental groups, and regulated entities have roundly criticized the DPS Policy – particularly the focus of the ESU determination “on genetics and adaptation.” Derek O. Teaney, The Insignificant Killer Whale: A Case Study of Inherent Flaws in the Wildlife Services’ Distinct Population Segment Policy and a Proposed Solution, 34 Envtl. L. 647, 655 (Spring 2004) (citing opinions and law review articles).

[vi] 59 Fed. Reg. 65885 (Dec. 21, 1994).

[vii] DPS Policy at 4724.

[viii] Id. at 4725.

[ix] Alliance v. FWS, 2007 WL 286581, at *1 (citing DPS Policy at 4725).

[x] Id. (citing DPS Policy at 4725).

[xi] See id.

[xii] For a comprehensive analysis of the DPS Policy and courts’ application of that policy as of Spring 2004, see D. Teaney, The Insignificant Killer Whale, supra. See also Fund For Animals, Inc. v. Hogan,
428 F.3d 1059 (D. D.C. 2005) (addressing the FWS’ issuance of 90-day finding under the ESA detailing why trumpeter swans in three states were not a DPS, and dismissing plaintiffs claims under, inter alia, the ESA as moot); Inst. for Wildlife Prot. v. Norton, No. 04-35912, 174 Fed. Appx. 363, 2006 WL 536088 (9th Cir. March 3, 2006) (holding FWS’ decision not to recognize western sage grouse as a subspecies arbitrary and capricious, but holding FWS’ determination that the species was not a DPS was not arbitrary and capricious); Alsea Valley Alliance v. Dep’t of Commerce, 358 F.3d 1181 (9th Cir. 2004) (discussing the lower court’s holding that “[l]isting distinctions below that of subspecies or a DPS of a subspecies . . . are not allowed under the ESA.”) (internal citations omitted); Wyoming Farm Bureau Fed’n v. Babbitt, 199 F.3d 1224, 1239 & n.12 (10th Cir. 2000) (addressing listing below the species level in the context of experimental populations under ESA § 10(j), and finding that “[n]owhere does the [ESA] require the Secretary to designate experimental populations at the subspecies level.”). The Ninth Circuit’s opinion in Kern County Farm Bureau v. Allen, 450 F.3d 1072, 1979-81 (9th Cir. 2006), also contains a discussion of listing decisions under the species level, in the context of subspecies.

[xiii] 335 F.3d 1097 (9th Cir. 2003).

[xiv] 40 F.3d 835 (9th Cir. 2003).

[xv] 296 F. Supp.2d 1223 (W.D. Wash. 2003).

[xvi] Id. at 1236 (citing Nat’l Ass'n of Home Builders v. Norton, 340 F.3d 835 (9th Cir. 2003)). The Western District subsequently dismissed a challenge to NMFS’ decision to list the Southern Residents as endangered in December 2006. See Linda Larson, U.S. District Court Dismisses Challenge to ESA Listing of Puget Sound Killer Whales.

[xvii] 257 F. Supp.2d 357 (D. Me. 2003)

[xviii] Id. at 387.

[xix] See, e.g., NWEA v. FWS I, 2004 WL 792805, at *3 (D. Or. March 16, 2004) (“The Ninth Circuit has not addressed the validity of the significance requirement [of the DPS Policy].”). As mentioned in the text above, in 2003, the Ninth Circuit addressed an as-applied challenge to a FWS DPS determination for pygmy owls in the state of Arizona. The opinion includes thorough discussions of both the “discreteness” and “significance” inquiries of the DPS analysis, but is limited to an as-applied challenge to a specific DPS decision. National Ass’n of Home Builders v. Norton, 340 F.3d 835, 842-44 (9th Cir. 2003) (holding that “the FWS did not arbitrarily find that the differences in the conservation status of pygmy-owls across the border [of the United States] satisfied the discreteness element of the DPS Policy.”); id. at 844-52 (concluding that “the FWS did not articulate a rational basis in the Listing Rule for its finding that the discrete Arizona pygmy-owl population is significant to its taxon as a whole under either the second or fourth significance factor.”). Thus, Home Builders v. Norton did not consider the general validity of any element of the DPS Policy. In contrast, the Ninth Circuit chose to consider the general validity of the significance requirements in Alliance v. FWS. The February 2, 2007 opinion indicates that the Court considers at least the significance requirement of the DPS Policy valid.

[xx] Alliance v. FWS, 2007 WL 286581, at *2 (citations to regulatory documents omitted).

[xxi] Id.

[xxii] The Washington Department of Fish & Wildlife (WDFW) added the western gray squirrel to Washington’s list of state-threatened species in 1993. The WDFW considers habitat loss and degradation, fluctuating food supplies, disease, and mortality (resulting from road-kill and illegal hunting) as threats to the species’ “persistence.” State law (RCW 77.15.130) protects nest trees used by western gray squirrels, and WDFW biologists will consult with landowners to protect and enhance oak/conifer habitat. WDFW, Species of Concern (last visited Feb. 5, 2007).

[xxiii] Alliance v. FWS, 2007 WL 286581, at *2 (listing populations).

[xxiv] See id.

[xxv] Id. at *3.

[xxvi] See id.

[xxvii] Id.

[xxviii] Id. at *4.

[xxix] Id. at *4, n.2 (emphasis in original).

[xxx] 467 U.S. 837 (1984).

[xxxi] Id. at 843.

[xxxii] Alliance v. FWS, 2007 WL 286581, at *4 (citing Chevron, 467 U.S. at 843; United States v. Mead Corp. 533 U.S. 218, 227-31 (2001)).

[xxxiii] Mead, 533 U.S. at 226-27.

[xxxiv] Alliance v. FWS, 2007 WL 286581, at *4.

[xxxv] Id. at *4, n.2.

[xxxvi] Id. at *3-5.

[xxxvii] Id. at *8.

[xxxviii] Id. at *7-12. The Service found that only the first, second and fourth factors of the DPS Policy’s test for significance warranted analysis (and that none established the Washington gray squirrel’s significance). The Court therefore assessed only those factors. See id. at *7.

[xxxix] Id. at *7-12.

[xl] Id. at *5 (citing proposal submitted by the General Accounting Office after the ESA was amended to encompass DPSs).

[xli] Id. (quoting S. Rep. No. 96-151, at 7 (1979)) (internal quotations and emphasis omitted).

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