FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

AMERICAN WILD HORSE

CAMPAIGN; KIMERLEE

CURYL,

Plaintiffs-Appellants,

v.

DAVID BERNHARDT,

Secretary of the Department

of the Interior; MICHAEL D.

NEDD; JILL C. SILVEY,

Defendants-Appellees.

No. 18-17403

D.C. No.

3:18-cv-00059-LRHCBC

OPINION

Appeal from the United States District Court

for the District of Nevada

Larry R. Hicks, District Judge, Presiding

Argued and Submitted April 29, 2020

San Francisco, California

Filed July 2, 2020

Before: Ronald Lee Gilman,* Susan P. Graber,

and Daniel P. Collins, Circuit Judges.

Opinion by Judge Graber

* The Honorable Ronald Lee Gilman, United States Circuit Judge for

the U.S. Court of Appeals for the Sixth Circuit, sitting by designation.
2 AM. WILD HORSE CAMPAIGN V. BERNHARDT

SUMMARY**

Wild Horses

The panel affirmed the district court’s summary judgment

in favor of federal defendants in an action alleging that the

Bureau of Land Management (“BLM”)’s “geld and release”

plan for wild horses violated the National Environmental

Policy Act (“NEPA”), the Administrative Procedure Act, and

the Wild Free-Roaming Horses and Burros Act. 

BLM developed a Gather Plan to address an excess of

wild horses. In 2017, BLM determined that there was an

overpopulation of wild horses in northeastern Nevada. It

developed a plan to restore ecological balance by adjusting

the sex ratio of the population, administering fertility control

treatments to mares, and gelding and releasing back to the

range some male horses.

The panel held that BLM did not act arbitrarily or

capriciously when it chose to geld and release some of the

male horses that would otherwise be permanently removed. 

The panel rejected plaintiffs’ arguments challenging BLM’s

actions and decisions.

Plaintiffs argued that BLM must prepare an

environmental impact statement (“EIS”) for its Gather Plan

because five of NEPA’s intensity factors demonstrated that

gelding and release would have significant effects on the

environment. First, an agency must prepare an EIS when its

** This summary constitutes no part of the opinion of the court. It has

been prepared by court staff for the convenience of the reader.
AM. WILD HORSE CAMPAIGN V. BERNHARDT 3

action will have “highly uncertain effects” on the

environment. The panel held that BLM’s plan to geld and

release male horses to the range did not meet that threshold.

The panel held that BLM used the existing evidence to assess

the level of uncertainty and made reasonable predictions

based on prior data to conclude that there would be no

significant environmental impact. Second, the panel held that

the effects of the Gather Plan were not “highly controversial.”

Third, the panel held that the Gather Plan did not exhibit

“unique characteristics;” and BLM’s determination that the

gather area was not in close “proximity to historic or cultural

resources” was not arbitrary or capricious. Fourth, the panel

held that the Gather Plan did not establish a “precedent” for

future actions where the plan did not establish gelding as an

accepted population management tool, nor was it the first

instance of BLM’s releasing geldings to the range. Fifth, the

panel held that because BLM followed the mandates of the

Wild Free-Roaming Horses and Burros Act, its decision to

geld and release did not “threaten a violation of federal law.”

The panel concluded that BLM permissibly determined that

the intensity factors did not show that the Gather Plan would

have a significant effect on the environment, and BLM

permissibly concluded that preparation of an EIS was not

required.

Plaintiffs argued that BLM acted arbitrarily and

capriciously because it did not address a Gelding Study, did

not consider the expert opinions that plaintiffs highlighted in

their public comments, and did not consider adequately a

National Academy of Sciences (“NAS”) Report on the wildhorses program. First, the panel held that BLM met NEPA’s

“hard look” standard when it considered and addressed the

relevant factor that the Gelding Study raised and explained

why additional information was not available. Second, the
4 AM. WILD HORSE CAMPAIGN V. BERNHARDT

panel held that The Wild Free-Roaming Horses and Burros

Act did not require BLM to discuss explicitly all expert

opinions submitted during the public-comment period. Third,

the panel held that by addressing the concerns and factors that

the NAS Report raised, BLM complied with the Wild FreeRoaming Horses and Burros Act’s requirement that BLM

“consult” the NAS to make determinations about how

appropriate management levels should be achieved.

COUNSEL

William N. Lawton (argued), Katherine A. Meyer, and

William S. Eubanks II, Eubanks & Associates LLC,

Washington, D.C., for Plaintiffs-Appellants.

Anna T. Katselas (argued), Devon Lea Flanagan, Daniela A.

Arregui, Holly A. Vance, Andrea L. Berlowe, and Mark R.

Haag, Attorneys; Eric Grant, Deputy Assistant Attorney

General; Jeffrey Bossert Clark, Assistant Attorney General;

Environment and Natural Resources Division, United States

Department of Justice, Washington, D.C.; Nancy Zahedi,

Assistant Regional Solicitor, Pacific Southwest Region,

United States Bureau of Land Management, United States

Department of the Interior, Sacramento, California; for

Defendants-Appellees.
AM. WILD HORSE CAMPAIGN V. BERNHARDT 5

OPINION

GRABER, Circuit Judge:

Public lands in the American West are home to thousands

of wild, free-roaming horses. Congress tasked Defendants,

the Secretary of the Department of the Interior and officials

from the Bureau of Land Management (“BLM”), with

preserving these “living symbols of the historic and pioneer

spirit of the West,” while also balancing the needs of other

wildlife and livestock that depend on the resources of public

lands. 16 U.S.C. § 1331. When wild horses become too

numerous for the land to support, Congress has mandated that

BLM remove excess horses until it reestablishes ecological

balance. Id. § 1333.

In 2017, BLM determined that there was an

overpopulation of wild horses in northeastern Nevada, and it

developed a plan to restore ecological balance in the region. 

In an effort to remove as few horses as possible, BLM plans

to adjust the sex ratio of the population, administer fertility

control treatments to mares, and geld and release back to the

range some male horses.

Plaintiffs American Wild Horse Campaign and Kimerlee

Curyl objected to the “geld and release” component of the

plan and brought claims that BLM had violated the National

Environmental Policy Act (“NEPA”), the Administrative

Procedure Act, and the Wild Free-Roaming Horses and

Burros Act. We hold that BLM did not act arbitrarily and

capriciously and, accordingly, we affirm the district court’s

grant of summary judgment to Defendants.
6 AM. WILD HORSE CAMPAIGN V. BERNHARDT

BACKGROUND

A. Statutory and Historical Background

Congress enacted the Wild Free-Roaming Horses and

Burros Act (“the Act”) in 1971, when wild horses were “fast

disappearing from the American scene.” 16 U.S.C. § 1331. 

The Act extended federal protection to wild horses and

empowered BLM to manage horses roaming public ranges as

part of its management of public lands. But within only a few

years, the Act proved so successful at replenishing the

population of wild horses that “action [was] needed to

prevent [the] program from exceeding its goals and causing

animal habitat destruction.” H.R. Rep. No. 95-1122, 95th

Cong., 2d Sess. at 23 (1978).

In 1978, Congress amended the Act to increase BLM’s

authority to manage and remove excess horses from public

lands “to achieve and maintain a thriving natural ecological

balance.” 16 U.S.C. § 1333(a). The main purpose of the

amendments was “to cut back on the protection the Act

affords wild horses, and to reemphasize other uses of the

natural resources wild horses consume.” Am. Horse

Protection Ass’n v. Watt, 694 F.2d 1310, 1316 (9th Cir.

1982).

The amended Act directs the agency to maintain an

inventory of wild horses on public lands so that it can

determine whether “an overpopulation exists on a given area”

and whether “action is necessary to remove excess animals.” 

16 U.S.C. § 1333(b)(2). If BLM makes such a finding, the

agency “shall immediately remove excess animals from the

range so as to achieve appropriate management levels.” Id.

Removals must continue “until all excess animals have been
AM. WILD HORSE CAMPAIGN V. BERNHARDT 7

removed so as to restore a thriving natural ecological balance

to the range, and protect the range from the deterioration

associated with overpopulation.” Id. Although BLM must

remove excess horses when it faces an overpopulation, the

Act also grants BLM the authority to use other population

control methods, such as sterilization and natural controls, to

avoid overpopulation. Id. § 1333(b)(1); see In Def. of

Animals v. U.S. Dep’t of Interior, 751 F.3d 1054, 1065 &

n.16 (9th Cir. 2014) (noting that BLM has broad discretion in

removing excess animals). In deciding on appropriate

measures, BLM must consult with state wildlife agencies,

“individuals independent of Federal and State government as

have been recommended by the National Academy of

Sciences,” and others that BLM determines have “scientific

expertise and special knowledge.” 16 U.S.C. § 1333(b)(1). 

And “management activities shall be at the minimal feasible

level.” Id. § 1333(a).

In recent years, BLM regularly has had to remove, or

“gather,” horses from public lands to keep the population

within the appropriate management levels and to avoid the

degradation of rangeland resources and the suffering of wild

horses due to a lack of water and forage. Although the Act

allows excess horses to be adopted or euthanized, 16 U.S.C.

§ 1333(b)(2), adoption demand is insufficient to achieve

population control, and Congress effectively has prohibited

BLM from euthanizing healthy animals by prohibiting the

authorization of funds to do so. In Def. of Animals, 751 F.3d

at 1060 n.6. Instead, BLM keeps removed horses in longterm holding facilities for the remainder of their natural lives.

About a decade ago, to assist it in improving the wildhorses program, BLM commissioned a report from the

National Academy of Sciences (“NAS Report”) “to provide
8 AM. WILD HORSE CAMPAIGN V. BERNHARDT

BLM with a scientific evaluation of the program’s pressing

challenges.” The report, issued in 2013, evaluated various

methods of population control. It recommended that BLM

consider “changes in expression of sexual and social

behavior” when deciding whether to sterilize horses and

noted that the “ideal method would not eliminate sexual

behavior or change social structure substantially.” The report

concluded that “the methods judged most promising for

application to free-ranging horses or burros are PZP vaccines,

GonaCon vaccine,1and chemical vasectomy.” It noted,

however, that “testing [of chemical vasectomy] in captive

horses would be needed before widespread application in the

field.” As for gelding some males in a herd, the report

concluded that the effects on reproduction and behavior

“could not be predicted at the time [the] report was prepared.” 

The report stated that it was not clear how gelding “would be

better than [surgical] vasectomy, which does not affect

testosterone or male-type behaviors,” but the report

recognized that there are some risks to herds associated with

surgical vasectomy as well.

To gain a better understanding of gelding as a populationcontrol method and of its effects on herd behavior, BLM

began a five-year study in 2016 (“Gelding Study”). The

Gelding Study, conducted as part of a gather plan

implemented in Utah, will evaluate whether gelding is “an

effective approach to slowing the annual population growth

rate,” the effects “of maintaining a population of gelded

males on the behavior and spatial ecology of the overall

population,” and the “health and short-term survival” of the

1 PZP and GonaCon are immune-contraceptive vaccines. PZP

vaccines are administered to mares; GonaCon vaccines can be

administered to either male or female horses. 
AM. WILD HORSE CAMPAIGN V. BERNHARDT 9

geldings. This is the first study that has examined

specifically “the effect of gelding on the behavior of freeroaming wild horses” and the way in which geldings interact

with intact wild stallions. Data from the study will not be

analyzed until October 2020 at the earliest.

B. The Present Controversy

The Antelope and Triple B Complexes comprise about

2.8 million acres of public lands in northeastern Nevada and

are home to thousands of wild horses. More than a decade

ago, BLM established that those areas could sustain a total of

between 899 to 1,678 wild horses. In 2017, based on a

current inventory of the lands, BLM determined that the

Complexes contained an excess population of about 8,600

wild horses and that action was necessary to remove them. 

Once BLM made that determination, the Act required BLM

to “immediately remove excess animals.” 16 U.S.C.

§ 1333(b)(2).

BLM developed the Antelope and Triple B Complexes

Gather Plan (“Gather Plan”) to address the excess, while also

keeping its management activities to “the minimal feasible

level.” Under the Gather Plan, BLM will remove the excess

wild horses over a ten-year period. Horses will be gathered

in phases as necessary to achieve a core breeding population

at the low range of the appropriate management level. The

plan also calls for adjusting sex ratios and administering

fertility-control treatments to mares in order to slow

population growth rates and increase intervals between

gathers.

In an effort to reduce the number of horses that need to be

removed permanently from public lands and kept in long-
10 AM. WILD HORSE CAMPAIGN V. BERNHARDT

term holding facilities, BLM will geld some male horses and

release them back onto the range “where they can engage in

free-roaming behaviors.” By doing so, BLM can reduce the

breeding population to the low end of the appropriate

management level, but keep the total population of horses at

mid-range. The primary purpose of the gelding component

is not to slow population growth, but to allow more horses to

remain free-roaming than otherwise would be possible.

Gelding horses is a centuries-old practice. It has been

studied extensively and is a routine procedure. It also is one

of the few permanent fertility-control options, resulting in

fewer “handling occasions” compared to other impermanent

methods. The only unknown aspects of gelding—as

identified in the NAS Report and acknowledged by BLM in

the Gelding Study—concern how useful it proves to be as a

population-control method and how wild horses will respond

when geldings are released back to the range.

In 2017, BLM issued a preliminary environmental

assessment of the Gather Plan. 40 C.F.R. § 1508.9. BLM

received almost 5,000 public comments. Public comments

notified BLM of the concerns of experts on wild-horse

behavior about the negative effects of gelding wild horses. In

the final environmental assessment, BLM responded to those

comments and explained that the experts’ opinions were

speculative because none of them had conducted a study on

the topic. BLM concluded that the Gather Plan would not

significantly affect the human environment and, thus, that

BLM was not required to prepare an environmental impact

statement (“EIS”). In December 2017, BLM issued a finding

of no significant impact.
AM. WILD HORSE CAMPAIGN V. BERNHARDT 11

In this action, Plaintiffs challenge the “geld and release”

portion of the Gather Plan. Plaintiffs do not deny that there

are too many wild horses in the Complexes, that BLM is

required to address that overpopulation, that removal of some

horses from the range is appropriate, or that BLM established

appropriate management levels of wild horses for the

Complexes. Plaintiffs challenge only BLM’s choice to geld

and release some of the male horses that would otherwise be

permanently removed, arguing that the agency acted

arbitrarily and capriciously. The district court granted

summary judgment to Defendants on all claims. Plaintiffs

timely appeal.

STANDARDS OF REVIEW

We review de novo a district court’s grant of summary

judgment. McGinest v. GTE Serv. Corp., 360 F.3d 1103,

1112 (9th Cir. 2004).

We review agency decisions that allegedly violate NEPA

under the Administrative Procedure Act, and we set aside

those decisions only if they are “arbitrary, capricious, an

abuse of discretion, or otherwise not in accordance with law.” 

Native Ecosystems Council v. U.S. Forest Serv., 428 F.3d

1233, 1238 (9th Cir. 2005) (quoting 5 U.S.C. § 706(2)(A)).

In reviewing an agency’s decision not to prepare an EIS,

we “employ an arbitrary and capricious standard that requires

us to determine whether the agency has taken a ‘hard look’ at

the consequences of its actions, based [its decision] on a

consideration of the relevant factors, and provided a

convincing statement of reasons to explain why a project’s

impacts are insignificant.” Envtl. Prot. Info. Ctr. v. U.S.
12 AM. WILD HORSE CAMPAIGN V. BERNHARDT

Forest Serv. (EPIC), 451 F.3d 1005, 1009 (9th Cir. 2006)

(alteration in original) (internal quotation marks omitted).

DISCUSSION

Plaintiffs argue that BLM must prepare an EIS for the

Gather Plan because five of NEPA’s intensity factors

demonstrate that gelding and release would have significant

effects on the environment. Plaintiffs also argue that BLM

acted arbitrarily and capriciously because it authorized

gelding and release without considering all the relevant

evidence.

A. Intensity Factors

NEPA requires agencies to prepare an EIS for “major

Federal actions significantly affecting the quality of the

human environment.” 42 U.S.C. § 4332(c). To determine

whether an action will have significant effects, agencies may

prepare an environmental assessment that “[b]riefly

provide[s] sufficient evidence and analysis for determining

whether to prepare an [EIS].” 40 C.F.R. § 1508.9(a)(1). An

EIS is required if that process raises “substantial questions”

about whether an agency action will have a significant effect. 

Blue Mountains Biodiversity Project v. Blackwood, 161 F.3d

1208, 1212 (9th Cir. 1998). If the agency determines that an

EIS is unnecessary, it issues a finding of no significant

impact, which “briefly present[s] the reasons why an action

. . . will not have a significant effect on the human

environment.” 40 C.F.R. § 1508.13.

To determine whether an action “significantly” affects the

environment, agencies must consider both the “context” and

“intensity” of the possible effects. 40 C.F.R. § 1508.27. 
AM. WILD HORSE CAMPAIGN V. BERNHARDT 13

“Intensity” refers to the “severity of impact,” and NEPA

regulations include ten intensity factors that agencies must

consider. Id. An action may be, but is not necessarily,

“significant” if any one of those factors is met. Ctr. for

Biological Diversity v. Nat’l Highway Traffic Safety Admin.,

538 F.3d 1172, 1220 (9th Cir. 2008).

Plaintiffs argue that five intensity factors demonstrate that

the Gather Plan may have a significant impact: (1) the Plan

has highly uncertain effects; (2) the Plan has highly

controversial effects; (3) the area has unique characteristics;

(4) the decision establishes a precedent; and (5) the decision

threatens a violation of the Wild Free-Roaming Horses and

Burros Act. 40 C.F.R. § 1508.27(b)(3), (4), (5), (6), & (10). 

We disagree.

1. Highly Uncertain Effects

When the possible effects of an agency’s action are so

“highly uncertain” that they raise “substantial questions”

about whether the action will have a significant impact on the

environment, the agency must prepare an EIS. 40 C.F.R.

§ 1508.27(b)(5); Blue Mountains, 161 F.3d at 1212. NEPA

“regulations do not anticipate the need for an EIS anytime

there is some uncertainty, but only if the effects of the project

are ‘highly’ uncertain.” Ctr. for Biological Diversity v.

Kempthorne, 588 F.3d 701, 712 (9th Cir. 2009) (internal

quotation marks omitted).

BLM’s plan to geld and release male horses to the range

does not meet that threshold. Gelding horses is not a new

practice, and its effects are well understood. The

environmental assessment thoroughly reviewed the research

on the surgical procedure, on the effects of gelding on
14 AM. WILD HORSE CAMPAIGN V. BERNHARDT

domesticated and semi-feral horses, on the effects of

castration on other species, and on the natural social behavior

of wild horses. In that discussion, BLM acknowledged that

wild horses “are rarely gelded and released back into the

wild, resulting in few studies that have investigated their

behavior in free-roaming populations.” Thus, BLM used the

existing research to predict that those effects likely would be

insignificant.

Some “quotient of uncertainty . . . is always present when

making predictions about the natural world.” Id. And we

have upheld agency predictions despite some uncertainty. Id.

In Center for Biological Diversity, for example, we held that

the Fish and Wildlife Service made reasonable predictions,

based on prior data, about the effects of their regulation on

polar bears even though “the specter of climate change made

the Service’s prediction less certain than it would be

otherwise.” Id. That the agency did not have perfect

information and had to extrapolate did not make the possible

effects “highly uncertain” and did not require the preparation

of an EIS. Id.

Similarly, in EPIC, 451 F.3d 1005, and Native

Ecosystems Council, 428 F.3d 1233, we upheld the

reasonableness of agency predictions in the face of some

uncertainty. In EPIC, the precise effects on spotted owls

could not be “accurately described without additional

information,” but we held that the agency permissibly

declined to prepare an EIS because the agency provided

reasons, based on the available research, for the assumptions

that it made and for the conclusion that it drew: the effects

likely would be minor. 451 F.3d at 1011 (internal quotation

marks omitted). We also did not fault the agency for not

preparing an EIS in Native Ecosystems despite imperfect
AM. WILD HORSE CAMPAIGN V. BERNHARDT 15

information and some evidence that the project would have

negative effects on wildlife. We explained that “the presence

of some negative effects [does not] necessarily rise[] to the

level of demonstrating a significant effect on the

environment.” 428 F.3d at 1240.

The same general analysis applies here. While

acknowledging that available research was not perfectly

analogous, BLM used the existing evidence to assess the level

of uncertainty and made “reasonable predictions on the basis

of prior data” to conclude that there would be no significant

environmental impact. Ctr.for Biological Diversity, 588 F.3d

at 712. BLM did not have to conclude that its project would

have no effect, but only that there were not substantial

questions as to whether gelding and release would have a

significant effect on the environment. Although the

environmental assessment did not always make BLM’s

reasoning explicit, we will “uphold a decision of less than

ideal clarity if the agency’s path may reasonably be

discerned.” Nat’l Ass’n of Home Builders v. Defs. of

Wildlife, 551 U.S. 644, 658 (2007) (internal quotation marks

omitted).

Exactly what role geldings will play within the wild-horse

population when they return to the range is unknown, but

BLM reasonably concluded that there was no reason to

expect any behavioral change in individual geldings to be

significant. BLM explained that, although geldings might

exhibit some behavioral differences, they will still be free to

roam unhindered and will have “a number of biological

impulses” compelling them to do so. Male horses take on a

number of different roles during their lives, so a change in a

gelding’s behavior post-castration would not necessarilyhave

a significant or adverse effect because the gelding could fit a
16 AM. WILD HORSE CAMPAIGN V. BERNHARDT

natural role other than reproducing. BLM further concluded

that the effects of gelding on individual horses would not be

more significant than the effects of the alternative—

permanently removing those horses from public lands.

BLM likewise considered the effects on family structures

among wild horses and reasonably concluded that there

would be no significant effects. BLM cited a study finding

that the presence of geldings did not disrupt relationships

between mares and foals. BLM further noted that the plan

will not geld a large enough number of males to substantially

reduce population growth rates. Because the number of

geldings will not be sufficient to affect reproductive patterns,

it is less likely that geldings would significantly affect other

family dynamics.

BLM provided a scientific foundation for its assumptions

and predictions. We defer to an agency’s “scientific

prediction[s] within the scope of its technical expertise.” Ctr.

for Biological Diversity, 588 F.3d at 712. Nothing in the

record, and none of Plaintiffs’ objections, undermines the

reasonableness of BLM’s conclusion.

Nor do our prior cases require a different result. In Bark

v. United States Forest Service, 958 F.3d 865, 869–71 (9th

Cir. 2020), we held that the Forest Service’s finding of no

significant effects was arbitrary and capricious because the

plaintiffs “pointed to numerous expert sources,” including

expert studies and research directly contrary to the agency’s

conclusion, and the agency failed to engage with that body of

research. By contrast, Plaintiffs have not identified any

evidence affirmatively showing that returning geldings to the

range would affect herd behavior. And BLM engaged with

the currently available scientific evidence either by discussing
AM. WILD HORSE CAMPAIGN V. BERNHARDT 17

the studies expressly or by addressing the concerns that the

research raised. See In Def. of Animals, 751 F.3d at 1072

(explaining that an agency must address crucial factors, but

not necessarily specific evidence regarding that factor).

Plaintiffs point to the NAS Report as evidence of

potentially significant effects. But that report acknowledged

the dearth of applicable scientific evidence and was

ultimately inconclusive. The report explained that “maletype aggressive and sexual behaviors are usually reduced” in

geldings but that the response varies by individual horse. It

concluded that whether gelding and release would “increase

aggression and competition in herds or decrease it” was

uncertain.

Only one study of domestic horses found increased

aggression in geldings. But, as BLM noted, wild male horses

naturally have varying levels of testosterone and behavior

depending on a variety of factors. Some change in behavior

among released geldings, then, would not necessarily be

disruptive. And a single study does not per se suffice to

demonstrate highly uncertain effects. See In Def. of Animals,

751 F.3d at 1071 (finding that the effects of administering

PZP to horses were not “highly uncertain” despite two studies

discussing the possible negative effects of PZP on herd

behavior); Native Ecosystems, 428 F.3d at 1240 (“[T]he

presence of some negative effects [does not] necessarily rise[]

to the level of demonstrating a significant effect on the

environment.”).

Finally, there was no other available information that

BLM should, or could, have used to reduce the uncertainty

about the effects of gelding and release. Data from BLM’s

Gelding Study will not be analyzed until later this year. And
18 AM. WILD HORSE CAMPAIGN V. BERNHARDT

the mere fact that BLM chose to study the effects of gelding

and release is not evidence that the effects on herd behavior

are highly uncertain or might be significant. The study will

provide information not only about the effects on herd

behavior, but also about the effectiveness of gelding as a

population control method. Because the Gather Plan’s use of

gelding was not primarily intended as a population control

tool, any uncertainty regarding gelding’s effect on population

growth is not significant. The Gelding Study reveals BLM’s

opinion that the effects on herd behavior are not fully

understood but does not suggest that BLM expects the effects

to be significant—or even that there will be an effect at all.

For that reason, our decision in National Parks &

Conservation Ass’n v. Babbitt, 241 F.3d 722 (9th Cir. 2001),

abrogated on other grounds as recognized by Monsanto Co.

v. Geertson Seed Farms, 561 U.S. 139, 157 (2010), is

inapposite. In that case, although the effects of the proposed

action were uncertain to some extent, the scientific evidence

revealed definite adverse effects. Id. at 732. The uncertainty

was over the intensity of the effects, id., and “[n]o new

scientific developments [were] required in order to obtain the

requisite information,” id. at 735. Under those circumstances,

the preparation of an EIS could help decision-makers better

understand the effects of the project.

Similarly, in Ocean Advocates v. United States Army

Corps of Engineers, 402 F.3d 846, 867 (9th Cir. 2005), we

identified evidence in the record that the agency’s action

would have an “unquestionably severe” effect on the

environment. We noted that the agency failed to collect

available data, conduct projection analyses, or provide a

“justification regarding why more definitive information

could not be provided.” Id. at 870–71 (internal quotation
AM. WILD HORSE CAMPAIGN V. BERNHARDT 19

marks omitted). Here, by contrast, the uncertainty is whether

gelding and release will have any effect at all on the behavior

of wild horses. BLM is not required to wait years before

taking action simply because an ongoing study might shine

light on an uncertainty that BLM reasonably predicts will be

minor or nonexistent.

After a thorough review of the evidence that was

available, BLM made “reasonable predictions” about the

relevant area of uncertainty. Ctr. for Biological Diversity,

588 F.3d at 712. Where there was no evidence that there

would be an effect, BLM was not required to conduct

additional research or wait for the results of the Gelding

Study before moving forward with its proposed action. The

NAS Report’s inconclusive statements and a single study

about domestic geldings does not undermine BLM’s

reasonable prediction that gelding and release will have

insignificant effects on herd behavior. BLM’s conclusion,

then, that the likelihood of significant effects of gelding was

not so uncertain as to require an EIS was not arbitrary or

capricious. EPIC, 451 F.3d at 1009. 

2. Highly Controversial

The effects of the Gather Plan are not “highly

controversial.” 40 C.F.R. § 1508.27(b)(4). The evidence that

Plaintiffs identify does not “cast[] serious doubt upon the

reasonableness of [the] agency’s conclusions.” Humane

Soc’y of U.S. v. Locke, 626 F.3d 1040, 1057 (9th Cir. 2010)

(internal quotation marks omitted). Plaintiffs have not

identified any evidence that contradicts BLM’s findings. The

NAS Report was inconclusive and reported no findings that

conflict directly with those in the environmental assessment. 

The expert opinions that Plaintiffs cite were not based on
20 AM. WILD HORSE CAMPAIGN V. BERNHARDT

studies that those experts had conducted, and no existing

research supported their speculation. Mere opposition to an

action does not, by itself, create a controversy within the

meaning of NEPA regulations. Id. BLM considered and

addressed the existing literature in its environmental

assessment and provided reasoning for its conclusions. That

satisfies NEPA. See Native Ecosystems, 428 F.3d at 1240

(“Simply because a challenger can cherry pick information

and data out of the administrative record to support its

position does not mean that a project is highly controversial

. . . .”).

3. Unique Characteristics

BLM’s determination that the gather area is not in close

“proximity to historic or cultural resources” was not arbitrary

or capricious. 40 C.F.R. § 1508.27(b)(3). Wild horses are

not a cultural resource for purposes of NEPA. Congress,

through the Wild Free-Roaming Horses and Burros Act,

decided how wild horses should be managed and how the

effects of agency actions on those horses should be evaluated. 

The Act states that wild horses will be considered “an integral

part of the natural system of the public lands,” 16 U.S.C.

§ 1331, and specifically instructs that they should be managed

“as components of the public lands” and as a part of a

“natural ecological balance.” Id. § 1333(a). A specific

statute, such as the Act’s directive as to how to manage wild

horses, governs over a general provision, such as NEPA. 

Perez-Martin v. Ashcroft, 394 F.3d 752, 758 (9th Cir. 2005);

see City & Cty. of San Francisco v. U.S. Citizenship &

Immigration Servs., 944 F.3d 773, 800 (9th Cir. 2019) (“We

cannot see how a general provision in one statute constrains

an agency given a specific charge in a subsequent law.”).
AM. WILD HORSE CAMPAIGN V. BERNHARDT 21

4. Precedent

The Gather Plan does not establish “a precedent for future

actions with significant effects,” nor does it represent “a

decision in principle about a future consideration.” 40 C.F.R.

§ 1508.27(b)(6). The Gather Plan does not establish gelding

as an accepted population-management tool, nor is it the first

instance of BLM’s releasing geldings to the range. The

conclusions in the environmental assessment for the Gather

Plan are specific to the scientific evidence that is currently

available. Like most environmental assessments, the Gather

Plan’s environmental assessment is “highly specific to the

project and the locale.” In Def. of Animals, 751 F.3d at 1071.

5. Threatens a Violation of Law

Finally, because BLM has followed the mandates of the

Wild Free-Roaming Horses and Burros Act, its decision to

geld and release does not threaten a violation of federal law. 

40 C.F.R. § 1508.27(b)(10). BLM adequately addressed the

relevant factors raised by the NAS Report and the expert

opinions submitted during the public comment period to

satisfy the requirements of the Act, as discussed in Parts B.2

and B.3, below.

We conclude that BLM permissibly determined that the

intensity factors, whether considered individually or

collectively, did not show that the Gather Plan would have a

significant effect on the environment. Accordingly, BLM

permissibly concluded that preparation of an EIS was not

required.
22 AM. WILD HORSE CAMPAIGN V. BERNHARDT

B. Authorization of Gelding and Release

Plaintiffs also argue that BLM acted arbitrarily and

capriciously because it did not address the Gelding Study, did

not consider the expert opinions that Plaintiffs highlighted in

their public comments, and did not consider adequately the

NAS Report.

1. Gelding Study

BLM did not discuss at length its Gelding Study in its

environmental assessment for the Gather Plan; nor did it wait

to authorize gelding and release until it obtained data from

the Study. But BLM considered and addressed the relevant

factor that the Gelding Study raised and explained why

additional information was not available, which meets

NEPA’s “hard look” standard. In Def. of Animals, 751 F.3d

at 1072–73.

BLM adequately considered the effect of releasing

geldings back to the range both on the geldings themselves

and on the rest of the wild-horse population. Because the

Gelding Study has not yet provided any new information on

the factor, it was reasonable for BLM not to mention that

study in the preliminary environmental assessment. 

Nevertheless, after BLM received comments that more

research was needed on the effects of gelding, it included a

brief discussion of the Gelding Study in its final

environmental assessment, explaining that results would not

be available for several years. BLM thus adequately

explained why additional data was unavailable. Cf. Ocean

Advocates, 402 F.3d at 870–71 (finding an agency’s failure to

collect available data or provide a “justification regarding
AM. WILD HORSE CAMPAIGN V. BERNHARDT 23

why more definitive information could not be provided” was

arbitrary and capricious).

The Gather Plan’s use of gelding also does not reflect an

unexplained inconsistency that would violate the

Administrative Procedure Act. See Humane Soc’y, 626 F.3d

at 1051 (concluding that an agency’s action was arbitrary and

capricious because the agency failed to explain inconsistent

factual findings). Plaintiffs argue that, in the environmental

assessment for the Gelding Study, BLM found that it needed

the results of that study before it could make informed

decisions about gelding wild horses. In Plaintiffs’ view,

because the Gather Plan included gelding and release without

explaining why BLM no longer deemed the Study’s results

necessary for informed decision-making, BLM acted

arbitrarily and capriciously.

BLM made no such finding in its environmental

assessment for the Gelding Study. That document merely

acknowledged that some uncertainty remained regarding the

effects of gelding on wild horses and that additional

information could improve its decision-making. The

intention of the Gelding Study is to augment BLM’s

understanding of gelding, not to dictate its future conduct and

decisions. The Gather Plan similarly includes measures to

help improve BLM’s understanding of gelding and release: 

BLM will monitor and observe the behavior of released

geldings to determine whether they are freely moving, how

they intermix with the breeding population, and if replacing

breeding mares with geldings can be an effective approach to

slowing the rate of population growth. Those plans are

consistent with BLM’s ongoing efforts to better understand

the effects of gelding, as described in the Gelding Study’s

environmental assessment. There was neither a change in
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practice nor an inconsistency with previous findings that

BLM was required to explain.

2. Expert Opinions

The Wild Free-Roaming Horses and Burros Act does not

require BLM to discuss explicitly all expert opinions

submitted during the public-comment period. See 16 U.S.C.

§ 1333(b)(1) (requiring that the agency consult individuals

recommended by the National Academy of Sciences, but

leaving it to the Secretary’s discretion whether to consult

“other individuals” with “scientific expertise and special

knowledge”). In its response to the public comments, BLM

provided reasons for not relying on those experts’ opinions

and referred to portions of the environmental assessment that

addressed those experts’ substantive concerns. That is a

sufficient explanation for us to conclude that BLM’s choice

was not arbitrary or capricious. See In Def. of Animals,

751 F.3d at 1073 (noting that we do not require an agency to

“recite its reasons for relying on the studies cited in [an

environmental assessment] as opposed to the studies cited by

[a] comment” to show that the agency “performed the ‘hard

look’ required by NEPA”).

3. National Academy of Sciences Report

By addressing the concerns and factors that the NAS

Report raised, BLM complied with the Wild Free-Roaming

Horses and Burros Act’s requirement that BLM “consult” the

National Academy of Sciences to make determinations about

how appropriate management levels should be achieved. 

16 U.S.C. § 1333(b)(1). The report concluded that “[t]he

effect that gelding a portion of the males in a herd would have

on reproduction and behavior could not be predicted at the
AM. WILD HORSE CAMPAIGN V. BERNHARDT 25

time this report was prepared.” BLM acknowledged that

uncertainty in the environmental assessment and discussed

the evidence of potentially adverse effects of gelding.

The only concern that BLM did not address expressly was

the NAS Report’s discussion of vasectomy as an alternative

to gelding. Public comments on the preliminary

environmental assessment brought this alternative to BLM’s

attention, but BLM did not address it in the final

environmental assessment, either. The NAS Report, though,

was ambivalent in its support of vasectomy, noting that

surgical vasectomy creates some risks to herds. And BLM’s

guidebook, which was included in the record, states that

vasectomies are not widely performed on stallions and that

additional research is needed to “perfect a safe technique”

and “demonstrate whether this approach will reduce

population growth rates”—reflecting a similar level of

uncertainty as with gelding.

Because evidence in the record supports BLM’s choice of

gelding, and because we can discern the reasons for BLM’s

rejection of the alternative of surgical vasectomy, Nat’l Ass’n

of Home Builders, 551 U.S. at 658, BLM’s failure to respond

explicitly to the comments about vasectomies was not

arbitrary or capricious. See In Def. of Animals, 751 F.3d

at 1072 (noting that NEPA does not require an agency “to

address in detail the substance conveyed in every single

comment made on an [environmental assessment] to prove

that the agency ‘considered’ the relevant factors”).

AFFIRMED.