Order Code RS21500
Updated July 16, 2003
CRS Report for Congress
Received through the CRS Web
The Endangered Species Act (ESA),
“Sound Science,” and the Courts
American Law Division
Decisions to list species under the Endangered Species Act (ESA) must rest only
on the best available scientific data, and science plays a part in other important aspects
of the Act. Yet many times the relevant science may be complex or incomplete. Recent
situations involving economic and social conflicts over resources have resulted in a
renewed focus on and criticism of how science is used under the ESA. This report
reviews how some courts have regarded these issues. It will be updated as
Background. The Endangered Species Act (ESA)1 was enacted to conserve listed
species – to bring them to the point where they do not need the special protections of the
Act2 – and to protect the ecosystems of which dwindling species are a part.3 Dwindling
species often reflect endangered resources or ecosystems. Recent situations4 in which
there have been economic and social disruptions as a result of listings under the ESA have
resulted in a renewed focus on the protective posture of the Act5 and on the use of science
under it. All agree that ESA decisions should be based on “sound science,”6 but that
phrase can mean different things to different people, and accusations of “junk science”
have been vigorously exchanged.
P.L. 93-205, 87 Stat. 884, 16 U.S.C. §§1531 et seq.
Section 3(3), 16 U.S.C. §1532.
Section 2(b), 16 U.S.C. §1531(b).
See, e.g., CRS Report RL31098, Klamath River Basin Issues: An Overview of Water Use
Conflicts, which discusses the conflicts over water use in that area.
See Tennessee Valley Authority v. Hill, 437 U.S. 153 (1978).
For a complete discussion of the use of science in general and agency scientific standards in
particular, see CRS Report RL31546: The Endangered Species Act and Science: the Case of
Congressional Research Service ˜ The Library of Congress
The ESA requires that decisions to list a species be made “solely on the basis of the
best scientific and commercial data available ....” There is no elaboration on the meaning
of this phrase in the law itself or in agency regulations, but the legislative history indicates
that science alone is to be the basis for listing decisions, although other factors may be
considered in post-listing decisions and actions.7 Science plays an important role in the
designation of critical habitat, in the consultation process, in the development of habitat
conservation plans and incidental take permits (that allow listed species to be killed under
certain conditions), and in the development of recovery plans.
However, given that the Act addresses species that almost by definition are likely to
be rare, there may be insufficient information on many species facing extinction, or
insufficient personnel or funds available to conduct necessary studies. What should be
done in such instances? The Act does not expressly address this question, but considering
the strongly protective purpose of the Act – to save and recover species – with the
wording of “best ... data available,” arguably the Act intends that all dwindling species
should be given the benefit of the doubt and a margin of safety provided. This is the
position taken in the conference report and agency documents.8 The Fish and Wildlife
Service (FWS) and NOAA Fisheries have developed joint policies on information
standards, use of expert opinions and peer review.9
Judicial review – in general. Judicial review can help ensure that an agency’s
use of scientific data and the decisions based on it are sound. Under the Administrative
Procedure Act, a court may set aside an agency’s decision if it is “arbitrary, capricious,
an abuse of discretion or otherwise not in accordance with law.”10 “Normally, an agency
rule would be arbitrary and capricious if the agency has relied on factors which Congress
has not intended it to consider, entirely failed to consider an important aspect of the
problem, offered an explanation for its decision that runs counter to the evidence before
the agency, or is so implausible that it could not be ascribed to a difference in view or the
product of agency expertise.”11 The agency must “examine the relevant data and
The word “solely” was deliberately added in the 1982 amendments to the ESA (P.L. 97-304,
96 Stat. 1411) to clarify that the determination of endangered or threatened status was intended
to be a biological decision made without reference to economic or other “non-biological” factors.
H.Rept. 97-567 at 19-20 (1982) discussed why listing was to be solely a scientific decision and
also interpreted “commercial data” as referring to trade data and not as inferring that economic
factors were to be considered. H.Rept. 97-835 at 19 (1982) confirms that it was the intent of both
chambers that economic factors not play a role in the designation and listing of species for
See Fish and Wildlife Service Handbook at 1-6 and H.R. Conf. Rep. No. 96-697 at 12 (1979),
which stated that the “best information available” language was intended to allow the FWS to
issue biological opinions even when inadequate information was available, rather than being
forced to issue negative opinions, thereby unduly impeding proposed actions. An agency has the
duty to show its actions will not jeopardize a species and a continuing obligation to make a
reasonable effort to develop additional information, and “to give the benefit of the doubt to the
59 Fed. Reg. 34271 (July 1, 1994).
5 U.S.C. § 706(2)(A).
Motor Vehicle Manufacturers Association v. State Farm Mutual Automobile Insurance Co.,
articulate a satisfactory explanation for its action including a rational connection between
the facts found and the choice made.”12 In reviewing agency action, the courts generally
are “highly deferential” to the agency.13 This is especially true with respect to matters,
such as scientific issues, that involve the agency’s particular expertise.14 These standards
may require that regulation under the ESA be rationally related to the problems causing
the decline of a species, especially when other interests are adversely affected.
Judicial review of the use of science. Courts that have considered the “best
data available” language have held that it does not require (and hence a court lacks the
authority to order) an agency to conduct studies to obtain missing data.15 However, an
agency cannot ignore available biological information,16 especially if the ignored
information is the most current,17 or is scientifically superior to that which the decisionmaker relied on. Nor can an agency treat one species differently from the way other
similarly-situated species are treated.18 The agency may not postpone listing a dwindling
species until it is on the brink of extinction in reliance on possible, but uncertain, future
actions of an agency.19 A court also has said that “the ‘best scientific and commercial data
available’ is not a standard of absolute certainty, and [is] a fact that reflects Congress’
intent that the FWS take conservation measures before a species is ‘conclusively’ headed
for extinction.”20 If the FWS does not base its listings on speculation or surmise, or
disregard superior data, the fact that the studies it does rely on are imperfect does not
undermine those authorities as the best scientific data available -- “ the Service must
utilize the best scientific ... data available, not the best scientific data possible.”21
On the other hand, an agency’s response must be appropriate to the problem; one
case struck down regulations that totally banned duck hunting in an area in order to
protect one species of duck.22 Another case stated that low numbers of a particular
species alone do not necessarily warrant listing – the reasons for the low numbers,
463 U.S. 29, 43 (1983); Okeeffe’s, Inc. v. U.S. Consumer Product Safety Commission, 92 F.3d
940, 942 (9th Cir. 1996).
Motor Vehicle Mfrs., supra, at 43; Dioxin/Organochlorine Center v. Clarke, 57 F. 3d 1517,
1525 (9th Cir. 1995).
Ethyl Corporation v. Environmental Protection Agency, 541 F. 2d 1, 34 (D.C. Cir. 19976), cert
denied, 426 U.S. 941 (1976).
Marsh v. Oregon Natural Resources Council, 490 U.S. 360, 377 (1989).
Southwest Center for Biological Diversity v. Babbitt, 215 F.3d 58 (D.C. Cir. 2000).
Connor v. Burford, 848 F.2d 1441 (9th Cir. 1988).
Southwest Center for Biological Diversity v. Babbitt, 926 F. Supp. 920 (D.C. Ariz. 1996).
Biodiversity Legal Foundation v. Babbitt, 943 F. Supp. 23 (D. D.C. 1996).
Defenders of Wildlife v. Babbitt, 958 F. Supp. 670, 680 (D. D.C. 1997).
Building Industry Ass’n of Sup. Cal. v. Norton, 247 F.3d 1241, 1246-1267 (D.C. Cir. 2001),
cert. denied 2002 U.S. LEXIS 479.
Connor v. Andrus, 453 F. Supp. 1037 (W.D. Tx. 1978).
whether the numbers are declining, and how experts view the population numbers must
Another court stated that the bar the FWS must clear in terms of evidence is very
low, but it must at least clear it and, in the context of issuance of “Incidental Take
Permits” under §10 of the Act, this means the agency must demonstrate that a species is
or could be in an area before regulating it, and must establish the causal connection
between the land use being regulated and harm to the species in question. Mere
speculation as to the potential for harm is not sufficient.24
Courts have held that the agencies basically must rely on existing regulatory
mechanisms in making listing determinations, and not on future or uncertain actions to
justify a decision not to list a species.25 In Oregon Natural Resources Council v. Daley
(ORNC),26 the court found that a NMFS rule determining the Oregon Coast salmon
Ecologically Significant Unit (ESU) not to be threatened was arbitrary and capricious in
that NMFS had relied on improper factors in reaching its decision and acted contrary to
the administrative record: NMFS had relied in part on a state plan to improve conditions
for the salmon that was voluntary and was to occur in the future,27resulting in a decision
that flew in the face of the agency’s scientific evaluations in the record. See also
Federation of Fly Fishers v. Daley,28 which agreed with the ONRC case regarding relying
on voluntary and future actions in the face of scientific studies indicating listing was
needed, but see also Defenders of Wildlife v. Babbitt,29 which did allow reliance in part
on cooperative conservation efforts in a case where the state plan was not the sole basis
for the agency’s decision.
A federal district court held in March 2002 that the economic analysis supporting a
designation of critical habitat was insufficiently specific.30 The court found that looking
only at the economic impacts that designation of critical habitat caused that were in excess
of those attributable to listing a species was illegal. The problem the court saw with the
agency approach is that the economic costs of listing that should be considered when
designating critical habitat wind up being left out of consideration entirely. (But see an
earlier decision, also in the district court for the District of Columbia, Trinity County
See Southwest Center for Biological Diversity v. Norton, Civ. Action No. 98-934, 2002 U.S.
Dist. LEXIS 13661, at *35 - *38 (D.D.C. July 29, 2002).
Arizona Cattle Growers Association v. United States Fish and Wildlife Service, 273 F.3d 1229
(9th Cir. 2001).
Southwest Center for Biological Diversity v. Norton, supra, at *27, citing Biodiversity Legal
Foundation v. Babbitt, 943 F. Supp. 23, 26 (D. D.C. 1996) and Oregon Natural Resources
Council v. Daley, 6 F. Supp. 2d 1139, 1153-1154 (D. Or. 1998).
6 F. Supp. 2d 1139 (D. Or. 1998)
Id., at 1154, 1158. Although there was a Memorandum of Agreement with the State, either
party could readily terminate it and additional action from the state legislature was required.
131 F. Supp. 2d 1158 (N.D. Cal. 2000).
97-CV-2330, 1999 U.S. Dist. LEXIS 10366 (S.D. Cal. 1999).
New Mexico Cattle Growers Association v. United States Fish and Wildlife Service, 248 F.
3d 1277 (10th Cir. 2001).
Concerned Citizens v. Babbitt, 92-1194 (D.D.C. September 20, 1993), which held that
consideration at the critical habitat stage of the costs associated with listing is prohibited
under the ESA.)31 Although the New Mexico Cattle Growers case related to habitat for a
bird, it has influenced another case related to salmon. A consent decree was approved
April 30, 2002 that vacated 19 critical habitat designations for salmon and steelhead in
the district court case National Association of Home Builders v. Evans.32 In vacating the
designations, the court called “persuasive” the Tenth Circuit’s decisions in the New
Mexico Cattle Growers case.
Many cases have been filed involving water flows and uses in the Klamath River
Basin, and some have challenged the science underpinning the flow releases and operation
of federal water resources projects in the Upper Basin area and resulting effects on salmon
populations. Fishermen successfully obtained an injunction preventing the Bureau from
sending irrigation deliveries to the Upper Klamath Project when required downstream
flows were not met, until the Bureau completed ESA consultation on an operating plan.33
Suit has also been filed by the fishermen and others after the death of over 30,000 salmon
in 2002, claiming that the Bureau’s 10-year operating plan for the Klamath Project
violates the ESA. Several area counties, including Trinity, Humboldt, Arcata, Eureka,
Fortuna, and Del Norte, have joined the suit as friends of the court. The suit will probe
the science surrounding the plan and seeks to invalidate the Klamath Biological Opinion
(BiOp) and its reasonable and prudent alternative (RPA) for the 10-year plan. A NMFS
employee has given sworn pretrial testimony that NMFS ignored opinions of agency
biologists in approving the 10-year Plan and declined to conduct the analyses necessary
to demonstrate that the Plan would not jeopardize salmon.
Trinity River flows. Suit has also been filed to challenge the Record of Decision
setting Trinity River flows. The Trinity flows into the Klamath, but much of its water is
diverted and sent to California’s Central Valley. Some reports state that many of the fish
that died in the Klamath River in late summer 2002 were attempting to return to the
Trinity. In 1992 Congress ordered studies of Trinity fisheries and then Secretary Babbitt
decided in 2000 to send more water down the Trinity to scour the river and make the river
more habitable for salmon, which would have resulted in less water for the Central Valley
and Westlands Water District. A FWS study found that higher releases from Trinity Dam
would cool the Trinity River and counteract the warm Klamath downstream, making the
water safer for salmon. However, in Westlands Water District v. United States
Department of the Interior,34 plaintiffs raised several challenges to Interior’s
administration of the Trinity River Division of the Central Valley Project, alleging
“maladministration” of the ESA by both NMFS and FWS and various NEPA violations.
A preliminary injunction was issued on March 22, 2001 that limited releases down the
Trinity to 368,600AF annually. On December 9, 2002, the court in Westlands issued an
unpublished memorandum decision that, in the main, granted relief to the plaintiffs,
finding several defects in the Final EIS that accompanied the Record of Decision on the
On this subject see 7 Endangered Species & Wetlands Report, May, 2002, p.1.
00-2799 CKK (D.D.C. 2002)
Pacific Coast Federation of Fishermen’s Association v. U.S. Bureau of Reclamation, 138 F.
Supp. 2d 1228 (N.D. Cal. 2001).
2002 U.S. Dist. LEXIS 25905 (E.D. Cal. 2000).
Trinity, and with agency actions under the ESA. Notably, the court found that the FWS
exceeded its authority by requiring as one of the “reasonable and prudent measures”
(RPMs) set out by FWS as part of its incidental take statement regarding the long-term
operating plan for the Trinity that Interior prevent upstream movement of “X2" water
quality standard, thereby impermissibly requiring a major change in operations. Under
the relevant regulations, a reasonable and prudent measure could only require minor
changes. The court also set aside NMFS’ RPM, asserting that “[e]ssentially what NMFS
did was require that the Preferred Alternative be implemented to minimize the effects of
implementing the Preferred Alternative.”35 The court also faulted Interior’s choice of
flow levels because they were based on analysis that failed to consider non-flow measures
or secondary statutory objectives – grounds on which the court also faulted the EIS that
accompanied the Decision. The court, however, did note that the Secretary’s decision was
not arbitrary or capricious merely because the science on which it rested was not certain,
as long as the decision was based on the best available scientific data, however inexact.
The court also noted the congressional directions to restore the Trinity and to meet federal
obligations to the Tribes who had intervened as Defendants. Therefore, the court directed
Interior to expedite preparation of a Supplemental EIS within 120 days (which would be
in April, 2003) to cure the EIS defects, but enjoined flows in excess of 452,600 AF in the
meantime. The Hoopa Tribe has appealed, was denied a stay by the district court, and has
asked the appellate court for an emergency stay of the district court’s decision. The
district court did, however, authorize the Department to release up to an additional 50,000
AF of water if necessary in water year 2003. Although the Department has filed a Notice
of Appeal, it did not request either additional flows or a stay of the district court decision.
2002 U.S. Dist. LEXIS 25905 at *172 - 173. It is possible that the RPM required that certain
parts of the agency action (flow volumes) be undertaken immediately in order to minimize
adverse impacts that could result from implementation of other parts of the overall agency action
(gravel movement/stream rehabilitation).
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