FOR PUBLICATION



### UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT

A ME R I C A N W I L D H O R S E C AMP A I G

N ; KI ME R

L E E C UR YL , Plaintiffs-Appellants
,

v.

D A V I D B E R NHAR D T , Secretary of the Departm ent of the Interior; M I C HAE L D. N E D D ; J I L L C. S I LVEY , 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 L arry R. Hicks, District Judge, Presiding

Argued and Subm itted April 29, 2020 San Francisco, California

Filed July 2, 2020

B efore: Ronald Lee Gilm an, * Susan P. Graber, and Daniel P. Collins, Circuit Judges.

Opinion by Judge Graber

* The H onorable Ronald Lee Gilm an, United States Circuit Judge f o r the U.S. Court of Appeals for the Sixth Circuit, sitting by designation.A M

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SUMMARY * *

Wild Horses

The panel affirm ed the district court’s summ ary judgm ent in favor of federal defendants in an action al l eg i n g that the Bureau of Land Managem ent (“BLM”)’s “geld and release” plan for w ild horses v iolated th e N ational E nvironm ental Policy Act (“NEPA”), the Adm inistrative Procedure Act, and the W ild Free-Roam ing Horses and Burros Act.

BLM de v e l o p e d a Gather Plan to address an excess o f wild horses. In 2017, BLM d eterm ined that there was an overpopulation of wild h o rs e s in northeastern Nevada. It d ev e loped a p lan to restore ecological balance by adjusti n g the sex ratio of the population, adm inistering fertility control treatm ents to m ares, and gelding and r e l e a sing back to the range som e m ale horses.

Th e panel held that BLM did not act arbitrarily o r capriciously when it chose to geld and release som e of the

m ale ho rses that w ould otherwise be perm anently rem o ved. The panel rejected plaintiffs’ argum ents challenging BLM’s actions and decisions.

Plaintiffs argued that BLM must prepare an environm ental imp a ct statem ent (“EIS”) for its Gather Plan because five o f NEPA’s intensity factors dem onstrated that g elding and release would have significant effects on t h e environm en t

. First, an agency m ust prepare an EIS when its

** This summ ary constitutes no part o f the opinion of the court. It h as been prepared by court staff for the convenience of the reader.A M

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action will have “highly uncertai n effects” o n the environm ent. The panel he l d that BLM’s plan to geld and release m ale horses to the range did not m eet that threshold. The panel held that BLM used the existing evidence to assess the level of uncertainty and m ade reasonable p red i c ti ons based on prior data to conclude that there would be no significant environm ental im p act. Second, the panel held that the effects of the Gather Plan were not “highly controversial.” Third, the panel held that the Gather Pl a n did n ot exhibit “unique characteristics;” and BLM’s determ ination that the gather area was not in close “proxim ity to historic o r cultural resources” was not arbitrary o r capricious. Fourth, the panel held tha t th e Gather Plan did not establish a “precedent” for future actions where the plan d id not establish gelding as an accepted p opulation m anagem ent tool, nor was it the first instance of BLM’s releasing geldings to the range. Fifth, the panel held that because BLM followed the m andates of the W ild Free-Roam i n g Ho rses and B urros Act, its decision to geld and release did not “threaten a v iolation of federal law.” The panel concluded that BLM p e rm issibly determ ined that the intensity factors did not show that the Gather Plan would ha ve a significant effect on the environm ent, and BLM perm issibly concluded that preparation of an EI S wa s 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 p ublic comm ents, and did not consider adequately a National A cademy o f Sciences (“NAS”) Report on the wildhorses program

. First, the panel held that BLM m et NEPA’s “hard look” standard when it considered and a d dr e ssed the

r elevant factor that the Gelding Study raised and explaine d why additional inform ation was n ot available. Se co nd, theA M

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panel held th at The W ild Free-Roam ing Horses and Burros Act d id not require BLM to disc u ss explicitly all expert opinions subm itted during the public-comm ent period. Third, the p anel held that by addressing the concerns and factors that th e N AS R eport raised, BLM com plied with the W ild Fre e

Roam ing H orses and Burros A ct’s requirem ent tha t BLM “consult” the NAS to m ake determ inations about h ow appropriate m anagem ent levels should be achieved.

C OUNSEL

W illia m N. Lawton (argued), K atherine A. Meyer, and W illiam S. Eub an ks II, Eubanks & Associates LLC, W ashington, D.C., for Plaintiffs-Appellants.

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

. Arregui, Holly A

. Vance, Andrea L. Be r l o we, and Mark R. Haag, Attorneys; Eric G rant, Deputy Assistant Attorney General; Jeffrey Bossert Clark, As si stant Attorney G eneral; Environm ent and Natural Resources Division, United States Departm ent of Justice, W ashington, D.C.; Nancy Zahedi, Assistant Regional Solicitor
, Pacific Southwest Region, United States Bur eau of Land Managem ent, United States Departm ent of the Interior, Sacram ento, Californ i a; for Defendants-Appellees.A M

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OPINION

GRABER, Circuit Judge:

Public lands in the Am erican W est are hom e to thousands of wild, free-roam ing horses. C ongress taske d De fendants, the Secretary of the Departm ent o f the Interior and officials from the Bur e au of Land Managem ent (“BLM”), with preserving these “living sym b ols of the historic and pioneer spi rit of the W est,” 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 t oo
num erous for the land to support, Congress has m andated that BLM rem ove excess horses unti l i t reestablishes ecological balance. Id. § 1333.

In 20 1 7
, BLM determ ined that there w as an overpopulation of wild horses in northeastern Nevada, and it developed a plan to restore ecological balance in the region. In an effort to rem ove as few horses as possible, BLM plans to adjust the sex ratio of the populatio n , a dm inister fertility control treatm ents to m ares, and geld and release back to the range som e m ale horses.

Plaintiffs Am erican W ild Horse Cam paign and Kim erlee Curyl objected to the “geld and r elease” com ponent of the plan and brought claim s that BLM had violated the N ational Envi ronm ental Policy Act (“NEPA”), the Adm inistrative Procedure A ct, and the W ild Free-Roam ing Horses an d Burros Act. W e hold that BLM did not ac t a r b i t rarily and

c apriciously and, accordingly, we affirm the district court’s grant of summ ary judgm ent to Defendants.A M

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BACKGROUND

A. Statutory and Historical Background

Congress enacted the W ild Free-Roam ing Horses and Burros Act (“the Act”) in 1971, when w ild horses were “fast d isappearing from the Am erican scene.” 16 U.S.C. § 1 3 3 1

. The Act extended federal protection to wild hor s e s and

em powered BLM to m anage horses roam ing p ublic ranges as part of its m anagem ent o f p ublic lands. But w ithin only a few yea r s , th e Act proved so successful at replenishing the p opulation of wild horses that “action [was] need e d t o prevent [the] program from exceeding its goals and causing anim al h ab i tat destruction.” H.R. Rep. No. 95-1122, 95th Cong., 2d Sess. at 23 (1978).

In 1 978, C ongress am ended the Act to increas e BLM’s authority to m anage and rem ove excess horses from public lands “to achieve and m aintain a thriving natural ecological balance.” 16 U.S.C. § 1333 ( a). The m ain purpose of the

am endm ents was “to cut back on the pr otection the A ct affords wild horses, and to reem phasize other uses of the natural resources wild horses consum e.” Am. Ho rse Protection Ass’n v. Watt
, 694 F.2d 1310, 1316 (9th Cir. 1982).

The am ended Act directs the agency t o m aintain an inventory o f wild horses on public lands so that it can determ ine whether “an o verpopulation exists on a given area” and whether “action is necessary to rem ove excess anim als.” 16 U.S.C. § 1333(b)(2). If BLM m akes such a finding, the agency “shall imm ediately rem ove excess ani ma l s from the

r a n ge s o as to achieve appropriate m anagem ent levels.” Id

. Rem o vals m

ust continue “until all excess anim als have beenA M

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rem oved so as to restore a thriving natural ecological balance to the range, and protect the range from the deterioration associated with overpopulation.” Id. A lthough BLM m ust

rem ove excess horses when it faces an overpop ulation, the Act also g rants BLM the authority to use other population control m ethods, such as sterilization and natural controls, to avoid overpopulati o n

. Id. § 1333(b)(1); see In Def. of Animals v. U. S

. De p’t of Interior
, 751 F.3d 1054, 1065 & n.16 (9th Cir. 2014) (noting that BLM has broad discretion in

r e m oving excess anim als). In d eciding on appropria te

m easures, BLM m

u st consult wi th state wildlife agencies, “individuals independent of Federal and State governm ent as have been recomm ended by the National Academy o f Sciences,” and others that BLM determ ines have “scientific expertise and special knowledge.” 16 U .S.C. § 1333(b)(1). And “m anagem ent activities shall be at the m inim al feasible level.” Id. § 1333(a).

In recent y ears, BLM regularly h as had to rem ove, o r “gather,” horses f

ro m p ublic lands to keep the population within the appropriate managem ent levels and to avoid the degradation of rangeland resources and the suffering of wild h or s e s due to a lack of water and forage. Although the A ct allows excess horses to be adopted or euthanized, 16 U.S.C. § 1 3 3 3(b)(2), adoption dem and is insufficient to achieve population control, and Congress effectiv e ly has prohibited BLM from euthanizing healthy anim als by prohibiting the authorization o f funds to do so. In Def. of Animals
, 751 F.3d at 1 060 n.6. Instead, BLM k e e p s rem o ved horses in longterm holding facilities for the rem ainder of their natural lives.

About a decade ago, to assist it in im proving th e wi l d

horses program , BLM comm issioned a report fr o m the National Acad emy of S ciences (“NAS R eport”) “to provideA M

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BLM with a scientific evaluation of the program ’s p ress i n g challeng e s

. ” The report, issued in 2 013, evaluated v arious

m ethods of population control. I t r e comm ended that BLM

con sider “changes in expression of sexual and social b eh avior” when deciding whether to sterilize horses a n d noted th a t th e “ideal m ethod would not elim inate sexual behavior or change social structure substantially.” T h e report concluded that “ the m ethods judged m ost p rom ising for application to f

ree-ranging horses or b urros are P ZP v accines, GonaCon vaccine, 1 and chem ical vasectomy.” It n oted, ho wever, that “testing [of chem ical vasectomy] in captive horses would be needed before widespread application in the field.” As for gelding som e m ales in a h er d
, th e report concluded that the effects on rep r o duction and behavior “could not be predicted at the tim e [the] report was p repared.” The report stated that it was n ot clear how gelding “would be better th a n [surgical] vasectomy, which does not affect t e s t osterone or m ale-type behaviors,” but the repor t recognized that there are som e risks to herds associated with surgical vasectom y as well.

To gain a b etter understanding of gelding as a populationcontrol m etho d a n d of its effects on herd behavior, BLM began a five-year study i n 2 016 (“Gelding Study”). The Gelding Study, c o nducted as part of a gather plan im plem ented in Utah, will evalua t e whether gelding is “an effe ctive approach to slowing the annual population growth rate,” the effects “of m aintaining a p o p ulation of gelded

m ales on the behavior and s p a t ia l ecology o f the overall population,” and the “health and short-term s urv ival” of the

1 PZP and G onaCon are im m une-contraceptive vac c i n e s

. PZP vaccines are adm inistered to m ares; GonaCon vaccines can be adm i nistered to either m ale or fem ale horses.A M

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geldings. This is the first study that h as exam ined specifically “the effect of gelding on the behavior of freeroam ing wild horses” and the way in which geldings interact with i n ta ct 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 Com p lexes com

prise about 2.8 m illion acres o f public lands in northeastern Nevada and

ar e h o me t o thousands of wild horses. More than a decade ago, B LM established that those areas could sustain a total o f between 899 to 1,678 w ild horses. In 2017, b ased on a current inventory of the lands, BLM determ ined that the Com plexes contained an excess population of about 8,600 wild horses and that action was n ecessary to rem ove them

. Once BLM m a d e th a t determ ination, the Act required BLM to “imm ediately rem ove excess anim als.” 16 U. S .C. § 1333(b)(2).

BLM developed the Antelope a n d Triple B Com plexes Gather Plan (“Gather Plan”) to address the excess, while also keeping its man agem ent activities to “the m inim al feasible level.” Under the Gather Plan, BLM will rem ove the excess wild horses over a ten-year perio d. Horses will be g athered in phases as necessary to achieve a core breeding population at the low range of the appropriate m anagem ent level. The p la n also calls for adjusting sex ratios and adm inistering fertility-control treatm ents to m ares in order to slow population growth rates and inc r ease intervals between gathers.

In an effort to reduce the num ber of horses that need to be

rem oved perm a nently from p ublic lands and kept in long-A M

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term holding facilities, BLM will geld som e m ale horses and release themback onto the range “where they can engage in free-roam ing behaviors.” B y doing so, B LM can reduce the b reeding population to the low end of the appropr i a te

m anagem ent level, but keep the total population of horses at mid-range. The prim ary p urpose of the gelding com ponen t is not to slow population growth, b ut to allow m ore horses to

rem ain free-roam ing than otherwise would be possible.

Gelding horses is a cen tur i es

- old practice. It has been studied extensively and is a routine procedure. It also is o ne of the few perm anent fertility-control o ptions, resulting in fewer “handling occasions” com pared to other im

perm anent

me thods. The only unknown aspects of gelding—a s identified in the NAS Report and acknowledged by BLM in the Gelding Stu dy

— c o ncern how useful it proves to b e as a population-control m ethod and how wild horses will respond when geldings are released back to the range.

In 2017, BLM issued a p relim inary e n vironm ental

assessm ent of the Gather Plan. 4 0 C. F. R. § 1508.9. BLM

rec eived alm ost 5,000 public comm ents. Public comm ents notified BLM of the c oncerns o f experts on wild-horse behavior about the negative effects of gelding w ild horses. In the final environm ental assessm ent, BLM responded to those

comm ents and explained that th e experts’ opinions were speculative because none of them h a d c o n ducted a study on the topic. BLM con c l u d ed that the Gather Plan would not

s ignificantly affect the hum an environm ent and, thus, tha t BLM was not required to prep ar e a n environm ental im pact statem ent (“EIS”). In Decem ber 2017, BLM issued a finding of no significant impact.A M

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In this action, Plaintiffs challenge the “geld and release” p ortion of the Gather Plan. P laintiffs do not deny that th e r e
are too m any wild horses in the Com plexes, that B LM is required to address that overpopulation, that rem oval of som e horses from the range is appropriate, or that BLM established appropriate m anagem ent levels of wild horses fo r t h e Com plexes. Plaintiffs challenge only BLM’s choice to geld and release som e of the m ale horses that would otherwise be perm anently rem oved, ar g u ing that the agency acted

a r b itrarily and capriciously. The d istrict court granted

su mm ary judgm ent to Defendants on all claim s. Plaintiffs tim ely appeal.

STANDARDS OF REVIEW

We r e v i ew de novo a d istrict court’s grant of summ ary judgm ent. M

c Gi n est v. GTE Serv. Corp.
, 360 F.3d 1103, 1112 (9th Cir. 2004).

W e review agency decisions that allegedly violate N EPA under the Adm inistrative Procedur e Ac t , and we set aside those de c i s ions 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.
, 4 28 F. 3 d 1233, 1238 (9th Cir. 2005) (quoting 5 U.S.C. § 706(2)(A)).

In reviewing an agency’s decision n ot to prepare an EIS,

we “em ploy an arbitrary and capricious standard that requires

us to determ ine whether the agency has taken a ‘hard look’ at th e consequences of its actions, based [its d ecision] o n a consi d e ra tion of the relevant factors, and provided a convincing statem ent of reasons to explain why a pr oj e c t ’s im pacts are i n significant.” Envtl. Prot. Info. C tr. v. U .S.A M

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Forest S erv. (EPIC)
, 451 F.3d 1005, 1 009 (9th Cir. 2 006) (alteration in original) (internal quotation m arks om itted).

DISCUSSION

Plaintiffs argue that BLM m ust p repare an EIS for the Gather P lan becau s e five o f NEPA’s intensity factors dem onstrate that gelding and release would have significant effects on the environm en t

. Plaintiffs also argue that BLM acted arbitrarily and c ap r iciously because it authorized gelding and release without considering all the relevant evidence.

A. Intensity Factors

NEPA requires agen cies to prepare an EIS for “m ajor Federal actions signifi c a n tly affecting the quality of the hum an environm ent. ” 4 2 U.S.C. § 4332(c). To determ ine whether an action will have significant effects, agencies m ay prepare an environm en t a l assessm ent that “[b]riefly provide[s] su fficient evidence and analysis for determ ining 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 C ir. 1998). If the agency determ ines that an EIS is unnecessary, it issues a fi nd ing of n o significant im pact, which “briefly presen t[s ] the reasons why an action

. . . will not h ave a s ig n ificant effect on the hum an environm ent.” 40 C.F.R. § 1508.13.

T o d etermine whether an action “significantly” affects th e environm ent, agencies m

ust consider b oth the “context” and “intensity” o f the p ossible effects. 40 C.F.R. § 1 5 08.27.A M

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“Intensity” refers to the “severity of im pact,” and N EPA regulations include ten i ntensity factors that agencies m ust consider. Id. An action m ay be, but is n o t n ecessarily,

“ s ignificant” if any one o f those factors is m et. Ctr. f o r Biological D iversity v. Nat’l Highway Traffic Safety Admin.
, 538 F.3d 1172, 1220 (9th Cir. 2008).

Plaintiffs argue t

h at f iv e inten sity factors dem onstrate that the Gather Pl a n m ay have a significant im pact: (1) the Plan has highly uncertain effects; (2) the Plan h as highly controversial effects; (3) the area h as unique characteristics; (4) the decision establishes a p recedent; and (5) the decision threatens a violation of the W ild Free-Roam ing Horses and Burros Act. 40 C.F.R. § 1508.27(b)(3), (4), (5), (6), & (10). W e disagree.

1. Highly Uncertain Effects

When the possible effects of an agency’ s a c t ion are so “highly uncertain” that they raise “substantial questions” about whether the action will have a significant im pact on the

env i r on ment, the agency m u st prepare an EIS. 40 C.F.R. § 1508.27(b)(5); Blue Mountains
, 161 F.3d at 1 212. N EPA “regulati ons do not anticipate the need for an EIS anytim e there is som e uncertainty, but only if the effects of the project

are ‘h ig hly’ uncertain.” Ctr. for Biological Diversity v. Kempthorne
, 588 F.3d 7 01, 712 (9th Cir. 2009) (intern al quotation m arks om itted).

BLM’s plan to geld and release m ale horses to the range d oe s not m eet that threshold. Gelding horses is n ot a n e w practice, and its effects a re well understood. The environm ental assessm ent thoroughly reviewed the research

on the surgic al p r ocedure, on the effects of gelding onA M

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dom esticated and sem i-feral horses, on the effects o f castration on other species, and on the natural social behavior of wild horses. In that discussion, BLM acknowledg e d t hat wild horses “are rarely gelded and released b a c k into the wild, resulting in few studies that have investigated their behavior in free-roam ing populations.” Thus, BLM used the existing research to predict that those effects likely would be insignificant.

Som e “quotient of uncertainty

. . . is always present when

m a k i ng predictions about the natural world.” Id. And we have upheld agency predictions despite som e uncertainty. Id. In Center for Biological Diversity
, for exam ple, we held that the Fish and W ildlife Service ma de reasonable p redictions, based on prior data, about the effects of their regulation on polar bears even though “the specter of clim ate change m ade the Service ’ s prediction less certain than it w ould be otherwise.” Id. That the agency did not have perfect inform ation and had to extrapolate did n ot m ake the possible effects “highly uncertain” and did not require the p reparation of an EIS. Id.

Sim ilarly, in EPIC
, 4 51 F. 3 d 1005, and Native Ecosystems Council
, 428 F.3d 1233, we uphel d the

r e a s o nableness of agency predictions in the face of som e uncertainty. In EPIC
, the p recise effects on spotted owls could not b e “accurately described with o u t additional info rmation,” but w e held that the agency perm issibly declined to prepa r e a n EIS because the agency provided
reasons, based on the available research, for the assum ptions that it m ade and for the conclusi o n that it drew: the effects likely would be m inor. 451 F.3d at 1011 (internal quotation

m arks om itted). W e also d id not f ault the age n cy for not preparing an EI S in Native Ecosystems despite im perfectA M

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inform ation and som e evidence that the p r o j ect would have negative effects on wildlife. W e explained that “the presence of som e negative effects [does n ot] necessarily rise[] to the level of dem onstrating a s ignificant effect on the environm ent.” 428 F.3d at 1240.

The sam e general analysis applies here. While acknowledging that available r e s earch was not perfectly analo g o us, BLM used the existing evidence to assess the level of uncertainty and m ade “reasonable predictions on the basis of prior data” to conclude that there would be no significant

env iro nm ental im

p act. C tr. for B iological Diversity
, 5 88 F.3d at 712. BLM did not h ave to conclude that its project would have no effect, but only that there were n o t substantial qu estions as to whether gelding and release would hav e a signifi c a n t effect on the environm ent. A lthough the environm ental a s s essm ent did not always m ake BLM’s reasoning explicit, we will “up h o l d a decision of less than ideal clarity if the agency’s path m ay reasonably be d iscerned.” Nat’l Ass’n of Home Builders v. Defs. o f Wildlife
, 551 U.S. 644, 658 (2007) (internal q u otation m arks

om itted).

Exactly wh at role geldings will play within the wild-horse p op ul a t ion when they return to the range is unknown, but BLM reasonably concluded that there was no reason to expect any behavioral change in in d i v i dual geldings to be significant. BLM explained that, al th o u gh geldings m ight exhibit som e behavioral differences, they will still be f ree to

roam unhindered and will have “a num b er of biological i mp u lses” com

pelling them

to d o so. Male horses take on a
num ber of different roles d

uring their lives, so a change in a g eld in g ’ s behavior post-castratio n w o u ld n o t n ecessarily h av e
a significant or adverse effect b ecause the gelding could fit aA M

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natural role o ther than reproducing. BLM further concluded that the effects of gelding o n individual horses would n ot be

m ore significant than the effec t s of the alternative— perm anently rem oving those horses frompublic lands.

BLM likewise considered the effects on fam ily structures

am ong wild horses and reasonably concluded that there would be no significant effects

. BLM cited a study finding that the presence of g eld i n g s did not d isrupt relationships b et ween m ares and foals. B L M further noted that the plan will n ot geld a large enough num ber of m ales to substantially reduce population growth rates. Because the num b e r of geldings will n ot be sufficient to affect reproductive patterns, it is less likely that geldings would significantly affect other fam ily dynam ics.

BLM provided a scientific foundation for its assum ptions and predictions. W e defer to an age n cy’s “scientific prediction[s] within the scope of its technical expertise.” C tr. for Biological Di v ersity , 588 F.3d at 712. Nothing in the record, and non e of Plaintiffs’ objections, underm ines the reasonableness of BLM’s conclusion.

Nor d o o ur prior cases require a different result. In Bark

v. United States F

orest Service
, 958 F.3d 865, 869–71 (9th Cir. 2020), we held that the Forest Servi c e’s finding of no significant effects was arbitrary and capricious because the p laintiffs “pointed to num erous expert sources,” including expert studies and research directly contrary to the agency’s conclusion, and the agency failed to engage with that body o f research. By contrast, Plaintiffs have not identifie d any evidence affirm atively showing that returning geldings to the

ran g e wo u ld affect herd b ehavior. And BLM engaged with th e cu rren tly av ailab le scientific evid en ce eith er b y d iscu ssin gA M

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the studies expressly o r by addre ssing the concerns that the research raised. See In Def. of A nimals
, 751 F.3d at 1 072 (explaining th at an agency m ust address crucial factors, but not necessarily specific evidence regarding that factor).

Plaint i ffs point to the N AS Report as evidence o f potentially significant effects. But that report acknowledged the d earth of applicable scientific evi d ence and was ultim ately inconclusive. The report explained that “m aletype aggressive and sexual behaviors are usually reduced” in geldings but that the r es p o n s e varies by individual horse. It concluded that whether gelding and release would “increase aggression and com

petit io n in herds o r decrease it” was uncertain.

Onl y o n e study of dom estic horses found increased aggression in geldings. But, as BLM noted, wild m ale horses naturally have varyin g l evels o f testosterone and behavior depending o n a v ariety of factors. Som e change in behavior

am ong released geldings, then, w ould n o t necessarily be disruptive. An d a s i n g le study does not per se suffice to dem onstrate h ighly uncertain effects. See In Def. of Animals
, 751 F.3d at 1071 (finding that the effects of adm inistering PZP to horses were not “highly uncertain” despite two studies discussing the possible n egative effects of PZP on herd behavior); Native Ecosystems , 4 28 F.3d at 1240 (“[T]he presence of som e negative effects [ d o e s n o t] necessarily rise[] to the level of dem o nstrating a sign i fi c a n t effect o n the environm ent.”).

Finally, there was no other available inform a tion that BLM should, or could, have used to reduce th e un c er tainty about the effects of gelding and release. Data from BLM’s Gelding Study will not be analyzed until later this year. AndA M

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the m ere fact that BLM chose to study the effects of gelding and release is n ot evidence that the effe c t s on herd behavior

are highly uncertain or m i g ht be significant. The study will provide inform ation n ot o nly about the effect s on herd behavior, but also about the effectiveness of gelding as a population control m ethod. Because the Gather Plan’s use o f gelding was not prim arily intended as a pop u la tion control tool, any uncertainty regarding gelding’s effect on population growth is not significant. The G elding Study reveals BLM’s opinion that the effects on herd behavior are no t fully understood but does n ot 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 Na t i onal Pa rks & Conservation Ass’n v. B a bbitt
, 241 F .3d 722 (9th Cir. 2001), abrogated on other grounds as recognized by Monsanto Co.

v. Geertson Seed Farms
, 561 U.S. 1 39, 157 (2010), is inapposite. In that case, although the effects of the proposed action were uncertain to som e extent, the scientific evidence revealed definite adverse effects. Id. at 732. The uncertainty

was over the intensity o f the effects, id.
, and “[n]o new scientific developm ents [were] required in order to obtain the req u i site in f o rm ation,” id. at 735. Under those circum stan ces, the preparation of an EIS could help decision-m akers b e tter understand the effects of the project.

Si mi larly, in Ocean Advocates v. United States Army Corps of E

ngineers , 402 F.3d 846, 86 7 (9th Cir. 2005), we i d entified evidence in the record that the agency’s actio n would have an “unquestion ably severe” effect on the environm ent. W e noted that the agenc y failed to collect available data, conduct projection analyses, o r p rovide a “justification regarding why m ore definitive info rma tion could not be p rovided.” Id. at 870–71 (interna l quotationA M

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m arks om itted). Here, by contrast, the uncertainty is whether gelding and release will have any effect at all on the behavior of wild h orses. BLM is not required to wai t y e a r s before taking action sim

p ly because an ongoing study mi gh t shine light on an uncertainty that BLM reasonably predicts will be

m inor or nonexistent.

After a tho r ough review of the evidence that was availab l e , BLM m ade “reasonable predictions” about the relevant area of uncertainty. Ctr. for Biological Diversity
, 588 F .3d at 712. Where there wa s no evidence that there would be an effe c t , BLM was not required to conduct additional research o r wait for th e results of the Gelding Study before m oving forward with its proposed action. The NAS Report’s inconclusive statem ents and a s ingle study about d om estic geldings d oe s n o t underm ine BLM’s reasonabl e p r e diction that gelding and release will have insignificant effects on herd b ehavior. BLM’s conclusion, then, that the likelihood o f significant effects of gelding was not so uncertain as to require an EIS was not arbitrary o r capricious. EPIC
, 451 F.3d at 1009.

2. Highly Controversial

The effects o f the Gather Plan are not “h i ghly controversial.” 40 C.F.R. § 1508.27(b)(4). The evidence that Plaintiffs identify does n o t “cast[] serious doubt upon the

rea s o n ableness of [the] agency’s conclusions.” Humane Soc’y of U.S. v. L ocke
, 6 2 6 F. 3 d 1040, 1057 (9th Cir. 2 010) (internal quotation m arks om itt e d). Plaintiffs have not identified any evidence that contradicts BLM’s findings. The NAS R eport was inconclusive and reported no findings that conflict directly with those in the environm ental assessm ent. The expert opinions that Plaintiffs cite were n ot b a sed onA M

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studies that those experts had conducte d
, an d no existing research supported their speculation. Mere opposition to an
ac t i o n does not, by itself, create a controversy within the

m eaning of NEPA regulations. Id. BLM considered and addre ss ed the existing literature in its environm ental

assessm ent and provided reasoning for its conclusions. That satisfies NEPA. S

ee Native Ecosystems
, 428 F .3d at 1240 (“Sim ply because a challenger can cherry pick inform a t i on and data out of the a dm inistrative record to support its position does not m ean that a project is highly controversial . . . .”).

3. Unique Characteristics

BLM’s determ ination that the gather area is not in cl os e “proxim ity to historic o r cultural resources” was not arbitrary

or capricious. 40 C.F.R. § 1 508.27( b ) ( 3 )

. W ild horses are not a cultural r esource for p urposes of NEPA. Congress, through the W ild F ree

- Ro a m ing Horses and Burros Act, decided how w ild ho r se s should be m anaged and how the effects o f agency actions on those horses should b e evaluated. The Act states that wild horses will b e considered “an integral part of the n atural system of the public lands,” 1 6 U.S.C. § 1331, and specifically instructs t h at they should be m anaged “as com ponents o f the p ublic lands” and as a part of a “natural ecological b alance.” I d

. § 1333(a). A specific statute, such as the Act’s directive as to how to m anage 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 Francisc o v

. U.S. Citizenship & Immigration Servs.
, 944 F.3d 773, 8 00 (9th Cir. 2019) (“W e cannot see how a general provision in one statute constrains an agency given a specific charge in a subsequent law.”).A M

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4. Precedent

The Gather Plan does not establish “a precedent for future actions with significant effects,” nor does it represen t “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-m anagem ent tool, nor is it the first instance o f BLM’s releasing g e l d i n gs to the range. The conclusions in the environm ental assessm ent for the Gather Plan are specific to the scientific evi d ence that is currently available. Like m ost environm ental assessm ents, the Gather Plan’s environm ental assessm ent i s “ highly specific to the project and the locale.” In Def. of Animals
, 751 F.3d at 1071.

5. Threatens a Violation of Law

Finally, b ecause BLM has followed the m andates of the W ild Free-Roam i n g Ho rses and B urros 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 b y the N AS Report and the expert opinions subm itted during th e p u blic comm ent period to satisfy the requirem ents of the Act, as discussed in Parts B.2 and B.3, below.

W e conclude that BLM p erm issibly determ ined that the intensity factors, whether considered individually o r collectively, did not show that the Gather Plan would h ave a significant effect on the e n v ironm ent. Accordingly, BLM perm issibly concluded that prep a ra t i on of an EIS was not required.A M

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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 comm ents, and did not consider a d e qu ately the NAS Report.

1. Gelding Study

BLM did not discuss at length its Ge lding Study in its environm ental assessm ent 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

a dditional inform ation was not available, which m eets NEPA’s “hard look” standard. In Def. ofAnimals
, 751 F.3d at 1072–73.

BLM adequately considered the effect o f r e leasing geldings back t o th e range both o n the geldings them selves and o n the re s t o f th e wild-horse p opulation. Because the Gelding Study has not yet provided any new inform ation on the factor, it w as reasonabl e for BLM not to m ention that stu dy in the prelim inary environm ental assessm ent. Nevertheless, after BLM received comm ents that m ore research was n e e d e d on the effects of gelding, it included a brief discussion of the Gelding Study in it s fi n al environm ental assessm ent, explaining that results would not be a vailable for several y ears. BLM thus adequately explained why additional data was unavaila b l e

. C f. O cean Advocates
, 402 F.3d at 870–71 (finding an agency’s failure to collect avail abl e data or provide a “justification regardingA M

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why m ore definitive inform ation could not be provided” was arbitrary and capricious).

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

u n e x p l a i n e d i n c o n s i s t e n c y t h a t w o u l d v i o l a t e t h e Adm inistrative P rocedure Act. See Humane Soc’y
, 626 F.3d at 1051 (concluding that an agency’s action was arbitrary and capricious because the a g e n cy failed to explain inconsistent factual f indings). Plaintiffs argue that, in the environm ental

assessm ent for the Gelding Study, BLM found that it needed the r e s u l ts of that study before it could m ake inform ed decisions about gelding wild hors e s

. In Plaintiffs’ v iew, because the Gather Plan included gelding and release without explaining why B LM no longer deeme d th e Study’s results necessary for info rm ed decision-m aking, BLM acted arbitrarily and capriciously.

BLM m ade no such finding in its environm ent al

assessm ent f

or the G elding Study. That docum ent m erely acknowledged that som e uncertainty rem ained regarding the effects of g elding on wild horses and that additional inform ation could im

p r o ve its decision-m aking. The intention of the G elding Study is to augm ent BLM’s understanding of gelding, n ot to dictate its future conduct and decisions. The Gather Plan sim ilarly includes m easures to help improve B LM’s understanding of gelding and release: BLM will m onitor and observe the behavi o r o f released geldings to determ ine whether they a r e freely m oving, h ow they interm ix with the breeding p opulation, and if re p l acing breeding m ares with geldings can be an effective approach to slowing the rate of population growth. Those plans are consistent with BLM’s o ngoing efforts to better und e rstand the effects of gelding, as d escribed in the Gelding Study’s

e n v i r onm ental assessm ent. There was neither a change i nA M

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practice nor an inconsistency with prev i o u s findings that BLM was required to explain.

2. Expert Opinions

The W ild Free-Roam ing Horses and Burros Act d oes not

r equire BLM to discuss explicitly all expert opini o n s subm itted during the public-comm ent period. See 16 U.S.C. § 1333(b)(1) (requiring th a t the agency consult individuals

recomm ended by the National Aca demy of Sciences, but leaving it to the Secretary’s discretion whether to consult “other individuals” with “scienti fi c expertise and special knowledge”). In its response to the public com m ents, BLM p rovided reasons for not relying on those experts’ opi ni o n s and referred to portions o f the environm ental assessm ent that addressed th os e e x perts’ substantive concerns. That is a sufficient explanation for us to con clude that BLM’s choice

was not arbitrary or c apr i c i ous. 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 environm ental assessm ent] as o pposed to the studies cited by [a] comm ent” to show that the agency “perform ed the ‘hard look’ required by NEPA”).

3. National Academy of Sciences Report

By addressing the concerns and factors that the NAS Rep o rt raised, BLM com plied w ith the W ild Free-Roam ing Horses and Burros Act’s requirem ent that BLM “consult” the National A cademy o f S ciences to m ake d eterm inations about how appropriate m anagem ent levels should be achieved. 16 U.S.C. § 1333(b)(1). The report conclude d t h a t “[t]he effect that gelding a portion of the m ales in a herd w ould have

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time this report was p repared.” BLM acknowledged that uncertainty in the environm ental assessm e n t a nd discussed the evidence of potentially adverse effects of gelding.

The only concern that B L M did n ot address expressly was the NAS R eport’s discussion of vasectomy as an alternative to gel ding. Public comm ents on the prelim inary environm ental assessm ent brought this alternative to BLM’s attention, b ut BLM did n o t a d dress it in the final environm ental assessm ent, either. The N AS Report, though,

was am bivalent in its support of vasectomy, noting that surgical vasectomy creates som e risks to herds. And BLM’s guidebook, which was included in the reco rd, states that vasectom ies are n ot widely pe r fo rm ed on stallions and that additional research is needed to “perfect a safe t ec hnique” and “dem onstrate whether this app r o a c h will reduce population growth rates”—reflecting a sim ilar level o f uncertainty as with gelding.

Because evidence in the record supports BLM’s choice o f gelding, and b ecause we can discern the reasons for BLM’s rejection of the alternative of surgical vasectomy, Nat’l Ass’n of H o me Builders
, 551 U.S. at 658, BLM’s failure to respond explicitly to the comm ents abo u t vasectom ies was not arbitra ry or capricious. See In Def. of Animals
, 751 F.3d at 1072 (noting that NEPA does not require an agency “to address in de t a i l the substance conveyed in every single

comm ent m ade on an [environm ental assessm ent] to prove that the agency ‘considered’ the relevant factors”).

AFFIRMED.