                   FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

OREGON NATURAL RESOURCES                 
COUNCIL FUND; SIERRA CLUB, a
California nonprofit corporation;
HEADWATERS, an Oregon nonprofit
corporation,
               Plaintiffs-Appellants,
                 and
ERIC NAVICKAS,
                            Plaintiff,        No. 07-35110
                  v.                           D.C. No.
                                             CV-05-03004-PA
LINDA GOODMAN, Regional
Forester, Pacific Northwest                    OPINION
Region, U.S. Forest Service;
UNITED STATES FOREST SERVICE, a
federal agency,
              Defendants-Appellees,
MOUNT ASHLAND ASSOCIATION, dba
Ski Ashland,
              Defendant-intervenor-
                           Appellee.
                                         
      Appeal from the United States District Court
               for the District of Oregon
     Owen M. Panner, Senior District Judge, Presiding

                   Argued and Submitted
              July 11, 2007—Portland, Oregon

                  Filed September 24, 2007

   Before: Stephen Reinhardt, Cynthia Holcomb Hall, and
             Milan D. Smith, Jr., Circuit Judges.

                             13051
13052   OREGON NATURAL RESOURCES v. GOODMAN
        Opinion by Judge Milan D. Smith, Jr.
           OREGON NATURAL RESOURCES v. GOODMAN          13055


                         COUNSEL

Marianne Dugan, Eugene, Oregon, for the plaintiffs-
appellants.

Robert J. Lundman, United States Department of Justice,
Washington, D.C., for the defendants-appellees.

Robert A. Maynard, Perkins Coie LLP, Boise, Idaho, for the
defendant-intervenor-appellee.


                         OPINION

MILAN D. SMITH, JR., Circuit Judge:

   Appellants Oregon Natural Resources Council, the Sierra
Club and Headwaters (collectively, ONRC) challenge the
United States Forest Service’s (Forest Service) approval of
the proposed expansion of the Mount Ashland Ski Area
(MASA), located in Oregon’s Siskiyou Mountains within the
Rogue River and Klamath National Forests. The district court
granted summary judgment in favor of the Forest Service,
finding it had not violated the National Environmental Policy
Act (NEPA), 42 U.S.C. § 4321 et seq., or the National Forest
Management Act (NFMA), 16 U.S.C. § 1600 et seq., in
authorizing the MASA expansion. We hold that the Forest
Service failed to properly evaluate the impact of the proposed
MASA expansion on the Pacific fisher, in violation of both
the NEPA and the NFMA, and that it violated the NFMA by
failing to appropriately designate Riparian Reserves and
Restricted Watershed terrain, as required by the Rogue River
13056       OREGON NATURAL RESOURCES v. GOODMAN
National Forest Land and Resource Management Plan (Rogue
River LRMP) and the Northwest Forest Plan (NWFP).
Accordingly, we reverse the district court’s grant of summary
judgment in favor of the Forest Service and remand to the dis-
trict court for issuance of the injunction specified in this opin-
ion.

             FACTUAL BACKGROUND AND
               PROCEDURAL HISTORY

  MASA is a ski resort located approximately seven air miles
south of the City of Ashland, Oregon. The Mount Ashland
Association (MAA) operates MASA under a special use per-
mit issued to the City of Ashland by the Forest Service. The
City of Ashland, in turn, leases the ski area to the MAA.

   For over twenty years, MAA and the Forest Service have
explored the possibility of expanding MASA so as to accom-
modate beginner and intermediate skiers and snowboarders,
as well as tubing and other facility upgrades, in an effort to
ensure the ski area’s long-term economic viability. In 1991,
the Forest Service released a Final Environmental Impact
Statement and Record of Decision approving the general
expansion of the ski area, but not addressing the specifics of
any plan. In 1998, MAA submitted a detailed, proposed
expansion plan to the Forest Service. The Forest Service sub-
sequently solicited public comment concerning the proposed
project, and in 2000 and 2003 released draft Environmental
Impact Statements (EIS). During the comment periods, the
Environmental Protection Agency and members of the public
expressed concerns about the proposed project’s possible
effects on erosion and sedimentation, bio-diversity, watershed
resources and water quality. Concern was also voiced about
the proposed expansion’s possible impact on the Pacific
fisher, a small carnivore related to the mink, otter and marten
that inhabits certain old-growth forests, and other wildlife
species.
           OREGON NATURAL RESOURCES v. GOODMAN            13057
   In August 2004, the Forest Service released a Final Envi-
ronmental Impact Statement (FEIS) in which it analyzed six
expansion alternatives. Alternative 2 and Alternative 6 are the
only two expansion alternatives relevant to this appeal. Alter-
native 2 contemplates the MAA constructing two new chair-
lifts and two new surface lifts, clear-cutting seventy-one acres
for new ski runs, and clearing four additional acres for lift
corridors and staging areas, primarily within the western half
of the special use permit area. The proposed ski run develop-
ment would require the removal of approximately sixty-eight
acres of trees, which would generate 1,822 board feet of com-
mercial grade timber. Additionally under Alternative 2, water-
shed restoration projects would be implemented, including
structural storm water control and non-structural controls,
such as the controlled placement of woody material. Alterna-
tive 6, which is a variant of Alternative 2, envisions limiting
the environmental consequences of expansion in the Middle
Fork area by requiring MAA to use a lightweight, low ground
pressure machine to clear ski runs and lift runs. Alternative 6
would permit MAA to construct two chairlifts and two sur-
face lifts and to clear approximately sixty-five acres of new
ski run terrain.

   In September 2004, the Forest Service issued the Record of
Decision (ROD) for the MASA expansion, selecting Alterna-
tive 2 with some modifications adopted from Alternative 6. It
concluded that Alternative 2 would help ensure MASA’s
long-term economic viability, with acceptable physical, bio-
logical and human environmental consequences. The Forest
Service received twenty-eight notices of appeal to the ROD.
Among these was an appeal from Eugene Wier, a wildlife
biologist who had been employed by the Forest Service,
detailing his concern regarding the expansion’s impact on the
Pacific fisher. In December 2004, the Forest Service denied
all administrative appeals to the ROD.

   In January 2005, ONRC filed suit against the Forest Ser-
vice and Regional Forester Linda Goodman seeking declara-
13058       OREGON NATURAL RESOURCES v. GOODMAN
tory and injunctive relief on the grounds that the MASA
expansion project violated both the NEPA and the NFMA.
Specifically, ONRC contends that the Forest Service failed:
(1) to ensure the viability of the Pacific fisher, a sensitive spe-
cies; (2) to adequately consider and disclose the direct and
cumulative impacts on the Pacific fisher; (3) to analyze
whether the expansion will comply with wetlands laws; (4) to
adhere to Rogue River LRMP and NWFP standards and
guidelines for protecting watersheds and riparian areas; (5) to
disclose a potentially high rate of error in the model that it
used to estimate sediment impacts on the municipal water-
shed; and (6) to adequately disclose cumulative water quality
impact by utilizing a computer model without disclosing its
flaws, rather than cataloging and analyzing specific projects.

   On February 9, 2007, after considering cross-motions for
summary judgment, the district court entered summary judg-
ment against ONRC. The court found that the Forest Service’s
disclosure of potential erosion and water quality impacts in
the FEIS complied with the NEPA, and that the Forest Ser-
vice did not violate the NEPA or the NFMA by failing to dis-
cuss compliance with applicable laws governing wetlands in
the FEIS. It also found the Forest Service’s failure to classify
Land Hazard Zone 2 terrain as Riparian Reserve was harmless
and concluded that the proposed expansion satisfied the prin-
cipal Rogue River LRMP and NWFP requirements for land
designated Restricted Watershed and Riparian Reserve.
Lastly, the district court held that ONRC’s allegations regard-
ing the Pacific fisher “mostly rely on extra-record materials
that I have stricken, and events that post-date final approval
of the ROD.” ONRC filed a timely notice of appeal from the
district court’s judgment. We granted a stay of the district
court’s judgment for the duration of this appeal.

    JURISDICTION AND STANDARD OF REVIEW

  We have jurisdiction pursuant to 28 U.S.C. § 1291, and
review the district court’s grant of summary judgment de
             OREGON NATURAL RESOURCES v. GOODMAN          13059
novo. Lands Council v. Powell, 395 F.3d 1019, 1026 (9th Cir.
2005) (citing Covington v. Jefferson County, 358 F.3d 626,
641 n.22 (9th Cir. 2004)). “Agency decisions that allegedly
violate [the] NEPA and [the] NFMA are reviewed under the
Administrative Procedure Act (‘APA’), and may be set aside
only if they are ‘arbitrary, capricious, an abuse of discretion,
or otherwise not in accordance with law.’ ” Envtl. Prot. Info.
Ctr. v. U.S. Forest Serv., 451 F.3d 1005, 1008-09 (9th Cir.
2006) (quoting 5 U.S.C. § 706(2)(A)). Although our review
under this standard is deferential, the agency must nonetheless
“articulate a rational connection between the facts found and
the conclusions made.” Or. Natural Res. Council v. Lowe, 109
F.3d 521, 526 (9th Cir. 1997) (citing United States v. La.-Pac.
Corp., 967 F.2d 1372, 1376 (9th Cir. 1992)). Moreover, if an
agency “fails to consider an important aspect of a problem . . .
[or] offers an explanation for the decision that is contrary to
the evidence,” its action is “arbitrary and capricious.” Lands
Council, 395 F.3d at 1026 (citing Motor Vehicle Mfs. Ass’n
v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983)).

   We review a district court’s decision to exclude extra-
record evidence for abuse of discretion. Nw. Envtl. Advocates
v. Nat’l Marine Fisheries Serv., 460 F.3d 1125, 1133 (9th Cir.
2006).

                        DISCUSSION

A.     Statutory Background

  1.    National Environmental Policy Act

   The NEPA mandates that covered governmental entities
take a “hard look” at the environmental consequences of cer-
tain proposed actions. Lands Council, 395 F.3d at 1027. The
NEPA requires federal agencies to prepare an EIS for “major
Federal actions significantly affecting” the environment. 42
U.S.C. § 4332(2)(C). An EIS is a thorough analysis of the
potential environmental impacts that “provide[s] full and fair
13060        OREGON NATURAL RESOURCES v. GOODMAN
discussion of significant environmental impacts and . . .
inform[s] decisionmakers and the public of the reasonable
alternatives which would avoid or minimize adverse impacts
or enhance the quality of the human environment.” 40 C.F.R.
§ 1502.1; see also Lands Council v. McNair, 494 F.3d 771,
777 (9th Cir. 2007).

  2.    National Forest Management Act

   The NFMA imposes constraints on the Forest Service’s
management of national forests. See 16 U.S.C. §§ 1600-87;
see also Ecology Ctr., Inc. v. Austin, 430 F.3d 1057, 1062 (9th
Cir. 2005). Procedurally, it requires the Forest Service to
develop a land and resource management plan, also referred
to as a “forest plan,” for each forest it manages. 16 U.S.C.
§ 1604(a). The NFMA also requires that a forest plan “pro-
vide for diversity of plant and animal communities,” id.
§ 1604(g)(3)(B), and that “[f]ish and wildlife habitat shall be
managed to maintain viable populations of existing native and
desired non-native vertebrate species in the planning area,” 36
C.F.R. § 219.19 (2000); see also Envtl. Prot. Info. Ctr., 451
F.3d at 1017. Any action taken by the Forest Service in a
managed forest must comply with the NFMA and must also
be consistent with the governing forest plan. See Ecology Ctr.,
430 F.3d at 1062.

B.     The Pacific Fisher

  1.    NFMA Claim

   [1] The Forest Service designated the Pacific fisher a “sen-
sitive species” due to substantial population declines and the
possibility that the fisher could be listed as an “endangered
species” pursuant to the Endangered Species Act. See Endan-
gered and Threatened Wildlife and Plants; 12-month Finding
for a Petition to List the West Coast Distinct Population Seg-
ment of the Fisher, 69 Fed. Reg. 18770, 18770 (April 8, 2004)
(to be codified at 50 C.F.R. pt 17) (finding that the Pacific
            OREGON NATURAL RESOURCES v. GOODMAN            13061
fisher warrants protection as an endangered species under the
Endangered Species Act of 1973). Under the Rogue River
LRMP, species classified as “sensitive” must be managed by
the Forest Service to ensure that they do not become threat-
ened or endangered due to management activities. The Rogue
River LRMP requires that where sensitive species occur in
lands categorized as “Developed Recreation,” “the Biological
Evaluation process . . . will be used during project planning
to display the effects of proposed activities . . . [and] [w]here
such species are present, field evaluation data will be used to
determine the effects and recommend measures to ensure that
species viability is not jeopardized.” The Biological Evalua-
tion is a five-step process which requires the Forest Service
to conduct: “a) [a] [p]re-field review of existing information;
b) [f]ield reconnaissance of the project area; c)
[d]etermination of whether local populations listed and PETS
species will be affected by a project; d) [a]nalysis of signifi-
cance of project effects on local and total populations of listed
and PETS species; e) [w]hen step four cannot be completed
due to lack of information, a biological or botanical investiga-
tion is conducted to gather the information needed to com-
plete step four.” ONRC contends that the Forest Service
violated the NFMA by failing to abide by the Rogue River
LRMP’s requirement that it conduct a compliant Biological
Evaluation to determine the impact of the proposed MASA
expansion on the Pacific fisher. We agree and conclude that
the Forest Service’s evaluation of the Pacific fisher in the
MASA expansion area does not comply with the requirements
of the Rogue River LRMP and, therefore, violates the NFMA.

   [2] In 1999, Forest Service biologists prepared a Biological
Evaluation for the MASA expansion, which concluded that
there was no suitable fisher habitat within the proposed proj-
ect area and that no impact on fisher or fisher habitat was
expected. However, in 2001 and 2002, Eugene Wier, a Forest
Service field biologist, identified Pacific fisher within the
project area. Wier noted that the Pacific fisher’s presence on
Mount Ashland represented the furthest east and the highest
13062      OREGON NATURAL RESOURCES v. GOODMAN
elevation at which Pacific fisher had been found within the
Siskiyou Mountains. Despite Wier’s observations, the Forest
Service did not update or amend its 1999 Biological Evalua-
tion. The Forest Service addressed Wier’s discovery of the
Pacific fisher within the expansion area in the 2004 FEIS by
concluding that the project posed no threat to the Pacific
fisher because the expansion will impact less than one percent
of the similarly forested land within three miles. This conclu-
sion is based on an analysis of habitat in the proximity of the
project area rather than documented local and total fisher pop-
ulations.

   [3] We find that in this instance the Forest Service’s use of
habitat as a proxy for population violated the NFMA. We
have recently explained that species viability may be met by
estimating and preserving habitat “only where both the Forest
Service’s knowledge of what quality and quantity of habitat
is necessary to support the species and the Forest Service’s
method for measuring the existing amount of that habitat are
reasonably reliable and accurate.” Earth Island Inst. v. U.S.
Forest Serv., 442 F.3d 1147, 1175-76 (9th Cir. 2006) [herein-
after Earth Island II] (quoting Native Ecosystems Council v.
U.S. Forest Serv., 428 F.3d 1233, 1250 (9th Cir. 2005))
(emphasis added).

   In Earth Island II, we examined whether the Forest Service
appropriately relied on habitat monitoring for determining
populations trends of the black-backed woodpecker. Id. at
1175. Although the Forest Service’s final environmental
impact statement “discuss[ed] various studies of black-backed
woodpeckers that confirm[ed] their preference for burned for-
est habitat” and presented tables listing areas in the project
area “assumed to provide high and moderate capability habi-
tat,” we concluded that “[t]here is no indication that the USFS
consulted current or accurate field studies to arrive at these
numbers, and there is no identification of the methodology
used in determining what constitutes suitable habitat.” Id.
            OREGON NATURAL RESOURCES v. GOODMAN             13063
   [4] We find the Forest Service’s analysis of the quantity
and quality of the fisher habitat similarly devoid of supporting
or explanatory data. In its 2004 FEIS, the Forest Service
stated that “[o]f the land within three miles of the S[pecial]
U[se] P[ermit] area, 10,200 acres are in a condition class simi-
lar to the forested site where the fisher was photographed. The
68 acres of forested area that would be removed if Alternative
2 . . . is implemented, amount to .7% percent of the available
acres [of] habitat within three miles.”1 But other than com-
menting that it was similar to the environment in which the
fisher was actually found, the Forest Service offered little
explanation of its methodology for classifying the 10,200
acres in question as suitable fisher habitat.

   Furthermore, the 2004 FEIS explicitly states that “ecologi-
cal relationships between fisher and habitat are largely
unknown” and “[t]he use of habitat per seasonality and topog-
raphy is currently unknown in the S[pecial] U[se] P[ermit]
area.” Additionally, statements by two Forest Service biolo-
gists, Eugene Wier and William Zilinski, reveal that the For-
est Service had insufficient data and knowledge regarding (1)
the population of the Pacific fisher, and (2) the quantity and
quality of habitat preferred by the Pacific fisher to justify
using habitat as a proxy for population. Specifically, Wier
observed that the Forest Service “know[s] nothing about how
many individuals there are (within the Ashland Watershed or
in the greater population), where they nest, how large their
home ranges are, and what constitutes the core habitat within
the greater Ashland Watershed upon which these individuals
depend for future survival.” Zilinski stated that the docu-
mented fisher’s purpose in the expansion area was unknown:
“was it just foraging, investigating denning sites, or exploring
for new territory?”
  1
   “The FEIS also noted that overall, ‘[t]he Mt. Ashland LSR [Late-
Succession Reserve] has nearly 15,000 acres of high quality late-
successional habitat.’ ”
13064         OREGON NATURAL RESOURCES v. GOODMAN
   [5] Thus, given the dearth of information about the local
fisher population generally and the Forest Service’s failure to
explain adequately how it identified suitable fisher habitat, we
hold that the Forest Service’s habitat analysis was insufficient
to satisfy the demands of the Rogue River LRMP Biological
Evaluation process, and is in violation of the NFMA.2

  2.    NEPA Claims

   ONRC also argues that the Forest Service violated the
NEPA when it failed (1) to disclose the potential impact of
displacing the fisher and damaging habitat in the corridor
linking the Klamath-Siskiyou region and the Southern Cas-
cades, and (2) to discuss the effect future projects in the
MASA expansion area would have on the Pacific fisher. We
agree with ONRC.

   [6] In Marble Mountain Audubon Society v. Rice, 914 F.2d
179 (9th Cir. 1990), we held that the Forest Service’s failure
to discuss the importance of maintaining a biological corridor
in the Klamath National Forest violated the NEPA. Id. at 182.
We explained that “[a]lthough the FEIS acknowledges that
the Grider [Creek] drainage is a biological corridor, it does
not contain significant discussion of the corridor issue.” Id.
Here, we are presented with a similar problem. In this case,
the Forest Service acknowledged that there is a biological cor-
   2
     Although we hold that the district court erred in finding the Forest Ser-
vice complied with the Rogue River LRMP Biological Evaluation process,
we conclude that it did not abuse its discretion in striking Eugene Wier’s
declaration because his concerns and criticisms of the MASA expansion
with respect to the Pacific fisher were already presented in his administra-
tive appeal of the ROD. Wier’s declaration is not necessary (1) to deter-
mine whether the Forest Service considered all relevant factors and
explained its decisions; or (2) to explain technical terms or complex sub-
ject matter and, therefore, does not fall within the exceptions to the rule
limiting “[j]udicial review of an agency decision . . . to the administrative
record in existence at the time of the decision.” Sw. Ctr. for Biological
Diversity v. U.S. Forest Serv., 100 F.3d 1443, 1450 (9th Cir. 1996).
            OREGON NATURAL RESOURCES v. GOODMAN            13065
ridor linking the Klamath-Siskiyou region and the Southern
Cascades, and concluded that the expansion would have an
inconsequential effect on the fisher. The Forest Service failed
to meaningfully substantiate this finding.

   [7] The Forest Service attempts to distinguish Marble
Mountain on the basis that any impact on the biological corri-
dor would be minimal because MASA’s expansion would
impact less than thirty-seven acres of the biological corridor,
whereas in Marble Mountain more than 3,000 acres of the
biological corridor were at risk. We are not persuaded. While
the number of acres at risk here is certainly less than that in
Marble Mountain, the Forest Service has nonetheless failed to
disclose the methodology it employed to determine that the
expansion’s impact on the fisher would be inconsequential.
Merely disclosing the existence of a biological corridor is
inadequate. Id. Where the Forest Service concludes that a
project will not jeopardize a wildlife corridor, it must support
that conclusion with at least some study or analysis of how
the reduced corridor will affect the species at issue. Id.

   Turning to ONRC’s second NEPA claim, federal law
requires that an EIS must analyze “the impact on the environ-
ment which results from the incremental impact of the action
when added to other past, present, and reasonably foreseeable
future actions.” 40 C.F.R. § 1508.7; see also 40 C.F.R.
§ 1508.25. A necessary component of NEPA’s “hard look” is
“a sufficiently detailed catalogue of past, present, and future
projects, and [ ] adequate analysis about how these projects,
and differences between the projects, are thought to have
impacted the environment.” Lands Council, 395 F.3d at 1027-
28.

   [8] The Forest Service’s 2004 FEIS violates the NEPA
because it fails to adequately discuss the impact on the Pacific
fisher of two future projects: (1) the construction of nine miles
of new logging roads within three miles of the project area,
which will require the cutting of approximately 4,250 acres on
13066       OREGON NATURAL RESOURCES v. GOODMAN
the south side of Mount Ashland and (2) a habitat restoration
and fuel hazard reduction treatments, which include con-
trolled fires. The FEIS simply states that “[n]o adverse cumu-
lative effects are anticipated. The only future project[s]
anticipated near the S[pecial] U[se] P[ermit] area are the Ash-
land Watershed Protection Project, and Ashland Forest Resil-
iency, which is [sic] not likely to affect fisher (minimal
associated human use/disturbance).”

   The Forest Service argues that it did not have to detail these
projects’ impact on the fisher because the ski area expansion
is modest. We reject this justification. We have repeatedly
explained that generalized, conclusory assertions from agency
experts are not sufficient; the agency must provide the under-
lying data supporting the assertion in language intelligible to
the public. See Ocean Advocates v. U.S. Army Corps of
Eng’rs, 402 F.3d 846, 864 (9th Cir. 2005); Klamath-Siskiyou
Wildlands Ctr. v. Bureau of Land Mgmt., 387 F.3d 989, 996
(9th Cir. 2004). “[W]hile the conclusions of agency experts
are surely entitled to deference, NEPA documents are inade-
quate if they contain only narratives of expert opinions.”
Klamath-Siskiyou Wildlands Ctr., 387 F.3d at 996. More spe-
cifically, the NEPA explicitly requires a cumulative impact
analysis. A particular action may seem unimportant in isola-
tion, but that small action may have dire consequences when
combined with other actions. As we observed in Klamath-
Siskiyou Wildlands Center, “[s]ometimes the total impact
from a set of actions may be greater than the sum of the parts.
For example, the addition of a small amount of sediment to
a creek may have only a limited impact on salmon survival,
or perhaps no impact at all. But the addition of a small
amount here, a small amount there, and still more at another
point could add up to something with a much greater impact,
until there comes a point where even a marginal increase will
mean that no salmon survive.” Id. at 994 (emphasis in origi-
nal).

  We cannot excuse the Forest Service from the NEPA
requirement to include an adequate cumulative impact analy-
            OREGON NATURAL RESOURCES v. GOODMAN            13067
sis in the 2004 FEIS. Two future projects, the Ashland Forest
Resiliency Project (a logging project), and the Ashland
Watershed Protection Project (a habitat restoration and fuel
reduction project), are scheduled to occur in the vicinity of the
proposed MASA expansion. Though the Forest Service gener-
ally addressed the impact of these projects elsewhere in the
FEIS, it failed to discuss in detail their impact upon the fisher
as part of the cumulative impact analysis required by NEPA.
See Earth Island Inst. v. U.S. Forest Serv., 351 F.3d 1291,
1306-07 (9th Cir. 2003) (holding that a cumulative impact
analysis violated NEPA when a FEIS did not assess the role
of foreseeable future projects on remaining suitable spotted
owl habitat in a nearby home range core area within close
proximity to the project’s area).

C.   Riparian Reserves and Restricted Watershed Terrain

   [9] We next turn to ONRC’s claim that the Forest Service
violated the NFMA by failing to appropriately designate “Ri-
parian Reserves” and “Restricted Watershed” terrain as
required by the Rogue River LRMP and the NWFP. The rules
governing the Forest Service’s designation and management
of Riparian Reserves and watersheds are complex and over-
lapping. The principal source of these rules is the NWFP
itself, and, derivatively, the Aquatic Conservation Strategy
(ACS) adopted pursuant to the NWFP. Under the ACS, Ripar-
ian Reserves are essentially buffer zones along streams, lakes,
wetlands, and mudslide-risk areas, and “watersheds” are
aquatic habitats or other hydrologically important areas. See
Pac. Coast Fed’n of Fishermen’s Ass’ns, Inc. v. Nat’l Marine
Fisheries Serv., 265 F.3d 1028, 1031-32 (9th Cir. 2001). Rec-
ognizing that riparian terrain “offer[s] core areas of high qual-
ity stream habitat,” and that watersheds “are crucial to at-risk
fish species and stocks and provide high quality water,” the
ACS standards and guidelines “prohibit or regulate activities
in Riparian Reserves that retard or prevent attainment of the
Aquatic Conservation Strategy objectives.”
13068       OREGON NATURAL RESOURCES v. GOODMAN
   The Forest Service must, however, comply with more than
just the NWFP’s ACS. When the NWFP was enacted, it did
not completely displace existing forest management plans. In
addition to setting out its own standards and guidelines, the
NWFP also provides that the standards and guidelines of the
pre-existing individual forest management plans—including
the Rogue River LRMP— remain effective “where they are
more restrictive or provide greater benefits to late-
successional forest related species.” Accordingly, the Forest
Service must also comply with the Rogue River LRMP’s
more restrictive standards and guidelines for lands designated
Restricted Riparian, Management Strategy 26 (MS 26) and
for lands designated Restricted Watershed, Management
Strategy 22 (MS 22). These standards and guidelines include
the protection of all terrain within 100 feet horizontal distance
of perennial streams, wetlands and associated riparian vegeta-
tion (Restricted Riparian MS 26) and all acres “designated as
suitable for Municipal Supply Watershed” (Restricted Ripar-
ian MS 22). These guidelines further provide that “[w]hen
conflicts exist between watershed management and other
resources, the conflict will be resolved in the favor of the
watershed resource.”

   Designation of land as Riparian Reserve has significant
consequences for the management of that land. Specifically,
the Rogue River LRMP mandates that management activities
in Riparian Reserves should not exceed:

    a)   20% mineral soil exposed on soils classed as
         very slight, slight, or low or moderate erosion
         hazard soils;

    b)   10% exposure on high or severe erosion hazard
         soils;

    c)   7% exposure on very high or very severe ero-
         sion hazard soils.
           OREGON NATURAL RESOURCES v. GOODMAN           13069
Pursuant to the NWFP, ACS Standard and Guideline WR-3
further prohibits the Forest Service from “us[ing] mitigation
or planned restoration as a substitute for preventing habitat
degradation” within Riparian Reserves, and explains that
“[p]riority must be given to protecting existing high quality
habitat” rather than compensating “for management actions
that degrade existing habitat” through mitigation and restora-
tion.

   Designation of land as Restricted Watershed terrain also
has significant consequences. The Rogue River LRMP
includes specific soil disturbance standards and guidelines for
areas designated as Restricted Watershed terrain and requires
that management activities on Restricted Watershed MS 22
lands not exceed: “a) [f]orty percent mineral soil exposed on
soil classed as very slight, slight, low or moderate erosion
hazard soils; b) [t]hirty percent exposure on high or severe
erosion hazard soils; c) [f]ifteen percent exposure on very
high or very severe erosion hazard soils.”

  1.   Riparian Reserves

   The NWFP assigns the Riparian Reserve designation to
streams, ponds, lakes, and wetlands, including a buffer around
these waterways. Pursuant to the ACS, (and thus the NWFP),
lands that are “potentially unstable” must be designated and
managed as Riparian Reserve. Using a “Landslide Hazard
Zone” technique to assess geologic stability in the 2004 FEIS,
the Forest Service divided project terrain into four hazard
zones, wherein Landslide Hazard Zone 1 (LHZ 1) encom-
passed the highest risk terrain, and Landslide Hazard Zone 4
(LHZ 4) encompassed the lowest risk terrain. It designated
LHZ 1 land as Riparian Reserve, but exempted LHZ 2 land
from this designation.

  ONRC contends that (1) the Forest Service’s failure to des-
ignate the LHZ 2 land as Riparian Reserve violated the
NFMA because its finding that the land was not “potentially
13070       OREGON NATURAL RESOURCES v. GOODMAN
unstable” is contradicted by record evidence, and (2) this fail-
ure to make an appropriate designation resulted in further vio-
lations of the Rogue River LRMP, the NWFP (and ACS), and
the NFMA, because a proper designation as Riparian Reserve
would compel specific management practices to ensure that
the terrain is appropriately protected. We agree. Evidence in
the record clearly shows that debris flow landslides persis-
tently originate from LHZ 2 lands. The 2004 FEIS found that
LHZ 2 “is the second highest risk terrain” and concluded that
the risk of landslides in LHZ 2 is “moderate to high” and the
“sediment delivery potential” is “high.” Therefore, the Forest
Service has failed to demonstrated that LHZ 2 areas are not
“potentially unstable.”

   [10] The district court sought to avoid this conclusion by
reasoning that “[o]ne cannot make an omelet without breaking
a few eggs. The other action alternatives evaluated in the
2004 FEIS would impact fewer acres of land classified LHZ
1 or LHZ 2. However, the Forest Service decided that the pre-
ferred alternative will better meet the purpose and need of the
expansion project.” We disagree. “It is well-settled that the
Forest Service’s failure to comply with the provisions of a
Forest Plan is a violation of NFMA.” Native Ecosystems
Council v. U.S. Forest Serv., 418 F.3d 953, 961 (9th Cir.
2005). The Rogue River LRMP contains Riparian Reserve
requirements and the ACS explicitly requires that
“[w]atershed analysis and appropriate NEPA compliance is
required to change Riparian Reserve Boundaries in all water-
sheds,” but the Forest Service failed to comply with those
requirements. By failing to designate the LHZ 2 terrain as
Riparian Reserve, the Forest Service violated the NWFP, the
Rogue River LRMP, and the NFMA. Whether the acreage at
issue is relatively large or small is irrelevant to this inquiry—
relevant law contains no de minimis exceptions.

  2.    Restricted Watershed Terrain

  When the 1991 MASA Master Plan was approved, approxi-
mately thirty-five acres of land designated as Restricted
           OREGON NATURAL RESOURCES v. GOODMAN           13071
Watershed MS 22 was included in the Special Use Permit
area. In a 1998 letter discussing a MAA proposal to expand
MASA, the Forest Service stated that an amendment was
required to reclassify Restricted Watershed MA 22 land
included in the Special Use Permit area as Developed Recre-
ation Management Strategy 4 (MS 4) and indicated that
“[t]his will be accomplished with Forest Plan Amendment 8.”
A statement acknowledging the need “to adjust the manage-
ment allocation boundary from the 1990 Rogue River Forest
Land and Resource Management Plan” was thereafter pub-
lished in the Federal Register. Notices Dept. of Agriculture,
Forest Service, Mount Ashland Ski Area Expansion, Rogue
River National Forest, Jackson County, Oregon, 64 Fed. Reg.
55228, 55229 (Oct. 12, 1999). In 2000, the Forest Service
confirmed the existence of Restricted Watershed MS 22 land
within the expansion area and the need for an amendment to
the 2000 draft EIS, when it stated that “[t]his adjustment
changes (reduces) approximately 35 acres of Restricted
Watershed (as mapped in LRMP Alternative K), and re-
allocates to Developed Recreation, accounting for the 1991
expanded ski permit area boundary. The Developed Recre-
ation allocation associated with this area will increase from
870 to 905 acres.” The 2003 draft EIS also maintained that
“[a]llocations associated with the 1990 [Rogue River National
Forest] LRMP and the Mt. Ashland Ski Area primarily
involved Developed Recreation [MS 4], and Restricted
Watershed [MS 22].” However, in the 2004 FEIS, the Forest
Service asserted that the 1994 NWFP “amended” existing
Rogue River LRMP designations to “Administratively With-
drawn (Special Management)” and states that “this allocation
is complimentary to the Developed Recreation R[ogue]
R[iver] LRMP allocation.” We find no explanation in the
record that would resolve the conflict between this statement
and the Forest Service’s post-1994 statements concerning its
intention to reallocate by means of “Forest Plan Amendment
8.”

  [11] The district court correctly determined that part of the
ski area retains the Restricted Watershed MS 22 designation,
13072       OREGON NATURAL RESOURCES v. GOODMAN
but nevertheless found that “the Forest Service necessarily
intended” to depart from the Rogue River LRMP “when it
conceptually approved the expansion in 1991, and approved
the site-specific proposal in 2004.” ONRC asserts that the dis-
trict court erred in its holding because the NFMA clearly pro-
hibits a departure from the forest management plan without a
plan amendment. We concur. Because there is no amendment
to the Rogue River LRMP in the record permitting the con-
templated change to the Watershed, the Forest Service vio-
lated the NFMA by failing to ensure that the expansion will
comply with the Rogue River LRMP standards and guidelines
for Restricted Watershed MS 22 terrain.

  3.    New Developed Recreation Site

   ONRC also contends that the Forest Service violated the
Rogue River LRMP and the NFMA by authorizing develop-
ment facilities that will affect currently undeveloped riparian
habitat in the Middle Fork. ONRC argues that the Rogue
River LRMP explicitly prohibits “new developed recreation
sites” on Riparian Reserves. Emphasizing that the ski area
construction began in 1963, the Forest Service asserts that the
project is not a “new” recreation site but the expansion of an
existing site, and that the Riparian Reserve restriction does
not apply. We agree with the Forest Service.

   [12] In addition to being fully supported by the Riparian
Reserves language of the Rogue River LRMP, this conclusion
is also fully consistent with treatment of this issue in the
Restricted Watershed terrain portion of the Rogue River
LRMP. In the standards and guidelines for Restricted Water-
shed MS 22, the Rogue River LRMP provides that “[n]ew
developed recreation sites will not be constructed. Expansion
of existing recreation sites will be analyzed in project envi-
ronmental analysis.” While the second sentence does not
appear in the standard and guidelines for Riparian Reserve
MS 26, the two treatments are consistent and there is no rea-
son to treat them differently. We therefore hold that the term
            OREGON NATURAL RESOURCES v. GOODMAN             13073
“new” is intended to have a uniform meaning throughout the
Rogue River LRMP and that the prohibition therein of new
developed recreation sites in Riparian Reserves does not
apply to the MASA expansion.

D.   Remaining Claims

   [13] Lastly, we hold that the district court did not err in rul-
ing for the Forest Service on all of the remaining claims
raised by ONRC in its motion for summary judgment.

   We hold that the Forest Service did not violate the NEPA
requirement that the 2004 FEIS discuss or analyze potential
violations of all federal, state and local laws, which include
Oregon state wetland laws and regulations. The Forest Ser-
vice included in the FEIS a discussion of whether the pro-
posed expansion would violate federal and state laws, and
explicitly noted that state and local agencies would have regu-
latory responsibilities for many activities and actions in the
expansion project. Although the FEIS does not specifically
address Oregon’s unique regulatory program for wetlands, the
FEIS is clear that state approval is a condition of the project.
Thus, it would be “fly speck[ing]” to find a NEPA violation
on these grounds, and we decline to do so. See Ecology Ctr.,
430 F.3d at 1077.

   Second, we find that the Forest Service’s FEIS adequately
disclosed the shortcomings in the Water Erosion Prediction
Project (WEPP) models used to estimate sediment impacts on
the municipal watershed and, therefore, complied with NEPA.
The NEPA does not require the reviewing court to “decide
whether an [EIS] is based on the best scientific methodology
available,” Or. Envtl. Council v. Kunzman, 817 F.2d 484, 496
(9th Cir. 1987) (quoting Friends of Endangered Species v.
Jantzen, 760 F.2d 976, 986 (9th Cir. 1985)) (alteration in orig-
inal); rather the question is whether the FEIS adequately dis-
closed the model’s potential weakness. We agree with the
district court that it did. In Appendix H to the FEIS, the Forest
13074       OREGON NATURAL RESOURCES v. GOODMAN
Service outlined several limitations of the WEPP model: its
failure to account for the higher erosion rates that typically
occur during the first two years after disturbance; the fact that
its components are reasonably effective on the agricultural
rangelands for which the WEPP model was designed, but that
it has limitations when applied to forest lands; and the fact
that no watershed template is currently available. Thus,
because the NEPA requires adequate disclosure, not the best
scientific methodology available, we hold that the Forest Ser-
vice made adequate disclosures concerning the WEPP
model’s shortcomings.

   [14] Finally, the Forest Service relied upon another com-
puter model, the Equivalent Roadless Area (ERA) model, to
address cumulative watershed effects. ONRC asserts that the
Forest Service violated the NEPA by using the ERA model to
assess the cumulative impacts of the proposed project when
taken together with past projects in the affected area. The
ERA model simulates the current condition of the terrain in
the watershed which reflects the impact of past projects, and
the FEIS describes the ERA methodology and the results of
the analysis in detail. Because we do not question the method-
ology, but “defer[ ] instead to the agency’s expertise in devel-
oping the model,” an analysis that “consider[s] cumulative
watershed effects and provide[s] a significant amount of
quantified and detailed information” satisfies the NEPA.
Envtl. Prot. Info. Ctr., 451 F.3d at 1014 (citation omitted).
Accordingly, we find that the Forest Service did not violate
the NEPA by using the ERA model to analyze the cumulative
watershed impact of the MASA expansion.

E.   Injunctive Relief

   We have noted in other contexts that, “where the question
of injunctive relief raises intensely factual issues, the scope of
the injunction should be determined in the first instance by the
district court.” Nat’l Parks & Conservation Ass’n v. Babbitt,
241 F.3d 722, 738 (9th Cir. 2001) (internal quotation marks
             OREGON NATURAL RESOURCES v. GOODMAN                13075
and citation omitted). But where, as here, “there are no such
intensely factual issues and the scope of the injunction to
which [the plaintiff] is entitled is quite plain,” we may “de-
cide the injunction question on this appeal.” Id. at 739. “To
determine whether injunctive relief is appropriate, ‘even in
the context of environmental litigation,’ we apply ‘the tradi-
tional balance of harms analysis.’ ” Id. at 737 (quoting Forest
Conservation Council v. U.S. Forest Serv., 66 F.3d 1489,
1496 (9th Cir. 1995)). In this case, we conclude that ONRC
has shown the potential for irreparable harm to the Pacific
fisher should the project continue. The MASA expansion
would result in eliminating habitat that may be vital to the
preservation of the fisher population in the project area. Until
the Forest Service conducts a proper Biological Evaluation
establishing the size of the local fisher population and its rela-
tionship to its habitat, there remains a “sufficient possibility
of environmental harm” to justify injunctive relief. Id. at 738.3

   Similarly, until the Riparian Reserve and Restricted Water-
shed lands are properly classified and subjected to the addi-
tional scrutiny required by these classifications, the possibility
of environmental harm to the ecological health of the region’s
waterways remains. See id. at 738 n.18 (“[B]ecause NEPA
can do no more than require the agency to produce and con-
sider a proper EIS, the harm that NEPA intends to prevent is
imposed when a decision to which NEPA obligations attach
is made without the informed environmental consideration
that NEPA requires.”) (citing Sierra Club v. Marsh, 872 F.2d
497, 500 (1st Cir. 1989)).

   [15] MAA argues that these violations are insignificant and
are outweighed by the risk of financial harm should the proj-
ect be enjoined further. We disagree and find that in this case,
the risk of permanent ecological harm outweighs the tempo-
rary economic harm that MAA may suffer pending further
  3
    At oral argument, counsel for ONRC suggested that one year of addi-
tional study would likely be sufficient.
13076      OREGON NATURAL RESOURCES v. GOODMAN
study. We note in particular that this is not a case where an
injunction would halt ongoing economic activity but would
simply delay the expansion of an existing facility. See Lands
Council, 494 F.3d at 780 (noting that this court has “held time
and again that the public interest in preserving nature and
avoiding irreparable injury outweighs economic concerns”)
(citations omitted). We also conclude that in this case, the
public’s interest in preserving the environment favors injunc-
tive relief. See Earth Island II, 442 F.3d at 1177.

                      CONCLUSION

   We reverse the order of the district court granting summary
judgment in favor of the Forest Service. We remand the case
to the district court and instruct it to promptly enjoin the
MASA expansion project contemplated in the 2004 FEIS until
the Forest Service has corrected the NFMA and NEPA viola-
tions we find in this opinion.

  REVERSED AND REMANDED WITH INSTRUC-
TIONS.
