                  FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

THE LANDS COUNCIL; OREGON               
NATURAL RESOURCES COUNCIL;
HELLS CANYON PRESERVATION
COUNCIL, an Oregon nonprofit
corporation; SIERRA CLUB, a
California corporation,
               Plaintiffs-Appellants,
                 v.
KEVIN MARTIN, Forest Supervisor               No. 06-35781
of the Umatilla National Forest,                D.C. No.
U.S. Forest Service; UNITED
STATES FOREST SERVICE,                     CV-06-00229-LRS
                                             ORDER AND
             Defendants-Appellees,            AMENDED
                and                            OPINION
AMERICAN FOREST RESOURCE
COUNCIL, an Oregon corporation;
BOISE BUILDING SOLUTIONS
MANUFACTURING L.L.C., a
Washington limited liability
company; DODGE LOGGING, INC., an
Oregon corporation,
 Defendants-Intervenors-Appellees.
                                        
        Appeal from the United States District Court
          for the Eastern District of Washington
         Lonny R. Suko, District Judge, Presiding

                   Argued and Submitted
           February 5, 2007—Seattle, Washington

                  Filed February 12, 2007
                  Amended March 2, 2007

                             2371
2372             LANDS COUNCIL v. MARTIN
       Before: Susan P. Graber, Richard A. Paez, and
               Carlos T. Bea, Circuit Judges.

                 Opinion by Judge Graber
2374               LANDS COUNCIL v. MARTIN


                          COUNSEL

Ralph O. Bloemers, Cascade Resources Advocacy Group,
Portland, Oregon; Karen Lindholdt, University Legal Assis-
tance, Spokane, Washington, for the plaintiffs-appellants.

David C. Shilton, U.S. Department of Justice, Environment
and Natural Resources Division, Washington, D.C., for the
defendants-appellees.

Scott W. Horngren, Haglund Kelley Horngren Jones & Wil-
der, LLP, Portland, Oregon, for the defendants-intervenors-
appellees.


                           ORDER

  Defendants-Appellees’ letter dated February 15, 2007,
requesting that the court strike or correct portions of the opin-
ion is construed as a petition for panel rehearing and is
ordered filed. The mandate issued February 12, 2007, is
                   LANDS COUNCIL v. MARTIN                  2375
recalled to allow the court to rule on the petition for panel
rehearing.

  The Opinion filed on February 12, 2007, is amended as fol-
lows:

   On slip opinion page 1951, lines 17-18, change “Indeed,
the Forest Service’s own expert testified” to “For example,
Intervenors’ expert, on whom the district court relied, testi-
fied”.

  On slip opinion page 1952, line 9, change “given by the
Forest Service’s own expert,” to “given by Intervenors’
expert,”.

 With these amendments, the petition for panel rehearing is
DENIED. The mandate shall reissue forthwith.


                          OPINION

GRABER, Circuit Judge:

   Plaintiffs The Lands Council, Oregon Natural Resources
Council, Hells Canyon Preservation Council, and Sierra Club,
which are environmental organizations, appeal the district
court’s denial of a preliminary injunction to halt the imple-
mentation of several United States Forest Service post-fire
logging sales in the Umatilla National Forest. American For-
est Resource Council, Boise Building Solutions Manufactur-
ing, L.L.C., and Dodge Logging, Inc., which are a forestry
advocacy organization and logging companies, join Defen-
dants (the Forest Service and the Forest Supervisor of the
Umatilla National Forest) as intervenors. We hold that the dis-
trict court did not abuse its discretion in denying a preliminary
injunction on Plaintiffs’ claims under the National Environ-
mental Policy Act (“NEPA”), 42 U.S.C. §§ 4321-4370, but
2376                  LANDS COUNCIL v. MARTIN
that the district court did abuse its discretion, by applying an
erroneous legal standard, in denying a preliminary injunction
on Plaintiffs’ claims under the National Forest Management
Act (“NFMA”), 16 U.S.C. §§ 1600-1614.

         FACTUAL AND PROCEDURAL HISTORY

   In August 2005, a forest fire named the “School Fire”
burned approximately 51,000 acres in southeastern Washing-
ton, including 28,000 acres of the Umatilla National Forest.
Soon thereafter, the Forest Service began preparations for the
School Fire Salvage Recovery Project to harvest dead and
dying trees located within the burned areas of National Forest
lands.1 After two rounds of public comments, the Forest Ser-
vice released the Final Environmental Impact Statement
(“EIS” or “School Fire EIS”) on July 10, 2006, and issued a
Record of Decision on August 14, 2006.

   The School Fire EIS considered three alternatives: Alterna-
tive A contemplated no action; Alternative B permitted sal-
vage logging on 9,423 acres; and Alternative C permitted
salvage logging on 4,188 acres. The Forest Service chose
Alternative B, which includes logging on portions of two
uninventoried roadless areas, known informally as West
Tucannon and Upper Cummins Creek, each of which contains
between 1,000 and 5,000 acres.

   Because trees that are damaged or destroyed by fire depre-
ciate in value quickly, the Forest Service Chief issued an
Emergency Situation Determination pursuant to 36 C.F.R.
§ 215.10. That Determination authorized immediate logging
in three designated areas, premised on the prediction that “a
delay would result in a potential loss of value of $1,547,000
to the Federal Government.” The three sales—the Milly, Oli,
  1
   The project also includes construction of temporary roads and harvest-
ing of “danger trees.” Danger trees are trees that present a risk to public
safety, such as trees that are likely to fall on a road or building.
                      LANDS COUNCIL v. MARTIN                      2377
and Sun Salvage Timber Sales—are located in the most
severely burned areas of the forest. Together they comprise
3,674 acres, or slightly more than one-third of the total acre-
age scheduled for salvage logging under the EIS.

   On August 15, 2006, one day after the issuance of the
Record of Decision, Plaintiffs filed suit, alleging violations of
NEPA and NFMA. The following day, Plaintiffs filed a
motion for a temporary restraining order and preliminary
injunction concerning the Milly, Oli, and Sun Sales. After
briefing and oral argument, the district court denied Plaintiffs’
motion. They immediately appealed to this court, arguing that
the district court abused its discretion in denying a prelimi-
nary injunction.2

                   STANDARDS OF REVIEW

   A preliminary injunction is appropriate when a plaintiff
demonstrates “either: (1) a likelihood of success on the merits
and the possibility of irreparable injury; or (2) that serious
questions going to the merits were raised and the balance of
hardships tips sharply in [the plaintiff’s] favor.” Clear Chan-
nel Outdoor Inc. v. City of Los Angeles, 340 F.3d 810, 813
(9th Cir. 2003) (internal quotation marks omitted). These two
options represent extremes on a single continuum: “the less
certain the district court is of the likelihood of success on the
merits, the more plaintiffs must convince the district court that
the public interest and balance of hardships tip in their favor.”
Sw. Voter Registration Educ. Project v. Shelley, 344 F.3d 914,
918 (9th Cir. 2003) (en banc) (per curiam). Alternatively, we
have stated the general test as requiring a plaintiff to establish
  2
   Plaintiffs also had filed an emergency motion before this court under
Ninth Circuit Rule 27-3, seeking an injunction pending appeal. A divided
panel denied that motion in an unpublished order on September 18, 2006.
Although logging in the sales areas has now commenced, the parties agree
that logging will not be completed until the summer of 2007. This case is
therefore not moot.
2378                LANDS COUNCIL v. MARTIN
“(1) a strong likelihood of success on the merits, (2) the possi-
bility of irreparable injury to plaintiff if preliminary relief is
not granted, (3) a balance of hardships favoring the plaintiff,
and (4) advancement of the public interest (in certain cases).”
Johnson v. Cal. State Bd. of Accountancy, 72 F.3d 1427, 1430
(9th Cir. 1995) (internal quotation marks omitted).

   We review for abuse of discretion a district court’s decision
to grant or deny a preliminary injunction. Sw. Voter, 344 F.3d
at 918. This review is “limited and deferential,” and “[w]e do
not review the underlying merits of the case.” Id. (internal
quotation marks omitted). But the district court “necessarily
abuses its discretion when it bases its decision on an errone-
ous legal standard or on clearly erroneous findings of fact.”
Playmakers LLC v. ESPN, Inc., 376 F.3d 894, 896 (9th Cir.
2004) (internal quotation marks omitted).

                         DISCUSSION

A.     NEPA Claims

   Plaintiffs contend that the district court abused its discre-
tion by holding that the Forest Service adequately analyzed
and disclosed the effects of logging in the West Tucannon and
Upper Cummins Creek roadless areas. According to Plain-
tiffs, NEPA requires the Forest Service to analyze the effects
of significant logging on the roadless character of large road-
less areas, but the Forest Service failed to do so with respect
to the West Tucannon and Upper Cummins Creek roadless
areas, each of which encompasses more than 1,000 acres.
Although Plaintiffs may ultimately succeed on the merits, we
hold that the district court did not abuse its discretion in deny-
ing Plaintiffs’ motion for injunctive relief. We therefore
affirm the district court’s denial of a preliminary injunction on
this ground.

  Plaintiffs acknowledge, as they must, that both the West
Tucannon and Upper Cummins Creek roadless areas are unin-
                   LANDS COUNCIL v. MARTIN                  2379
ventoried and that each area contains less than 5,000 acres.
Plaintiffs also concede that the EIS prepared by the Forest
Service extensively analyzes the effects of logging generally,
includes maps disclosing the locations of the proposed log-
ging, and mentions that logging will occur in roadless areas.
Plaintiffs point out, however, that the EIS does not specifi-
cally name the West Tucannon and Upper Cummins Creek
roadless areas, does not describe the precise extent of logging
in roadless areas, and does not analyze the effect of logging
on the roadless character of these areas.

   [1] Roadless areas have been the subject of federal legisla-
tion at least since the passage of the Wilderness Act of 1964
(“Wilderness Act”), 16 U.S.C. §§ 1131-1136. In the 1970s,
two massive inventorying projects—“Roadless Area Review
and Evaluation” (“RARE I” and “RARE II”)—were
undertaken to catalogue roadless areas for possible inclusion
as wilderness areas under the Wilderness Act. Designation as
an “inventoried” roadless area can be a first step to designa-
tion as a wilderness area. See generally Nat’l Audubon Soc’y
v. U.S. Forest Serv., 46 F.3d 1437, 1439-40 (9th Cir. 1994)
(describing the history of inventoried roadless areas).
Although no additional large-scale inventorying projects have
been undertaken since RARE I and RARE II, roadless areas
that meet certain criteria continue to be designated as wilder-
ness areas. One relevant criterion for designation of a wilder-
ness area is the size of the pristine area: consideration is
appropriate if the area “has at least five thousand acres of land
or is of sufficient size as to make practicable its preservation
and use in an unimpaired condition.” 16 U.S.C. § 1131(c).

   [2] Consistent with that historical background, we have
held that NEPA may require some consideration of the effects
of logging on the roadless character of roadless areas in cases
involving inventoried roadless areas, Nat’l Audubon, 46 F.3d
at 1448, and uninventoried roadless areas that contain more
than 5,000 acres, Smith v. U.S. Forest Serv., 33 F.3d 1072,
1079 (9th Cir. 1994). We also have recognized that “the deci-
2380               LANDS COUNCIL v. MARTIN
sion to harvest timber on a previously undeveloped tract of
land is an irreversible and irretrievable decision which could
have serious environmental consequences.” Nat’l Audubon,
46 F.3d at 1448 (internal quotation marks omitted); see also
Smith, 33 F.3d at 1079 (stating that “the decision to harvest
timber in a 5,000 acre roadless area is environmentally signif-
icant”). In Smith, we held that NEPA requires the Forest Ser-
vice, “at the very least, to acknowledge the existence of the
5,000 acre roadless area.” 33 F.3d at 1079. Plaintiffs ask us
to extend these holdings to uninventoried roadless areas smal-
ler than 5,000 acres.

   [3] It is true that significant logging of a roadless area
“could have serious environmental consequences,” Nat’l
Audubon, 46 F.3d at 1448, even if the roadless area is neither
inventoried nor greater than 5,000 acres. The Wilderness Act
does not require an absolute minimum of 5,000 acres; it also
allows for designation where the area “is of sufficient size as
to make practicable its preservation and use in an unimpaired
condition.” 16 U.S.C. § 1131(c). The district court must care-
fully assess the qualities of the roadless areas in question and
the extent of analysis in the EIS to determine whether the
requirements of NEPA have been satisfied. On appeal from
the denial of a preliminary injunction, however, we do not
find a clear legal error by the district court.

   Furthermore, in contrast to this case, where the Forest Ser-
vice has already prepared an EIS, in Smith and National
Audubon the Forest Service had not prepared an EIS and was
relying on environmental assessments. We held that logging
in a roadless area—even an inventoried roadless area or a
roadless area greater than 5,000 acres—does not categorically
require an EIS. See Smith, 33 F.3d at 1079 (stating that our
remand in Nat’l Audubon was an implicit rejection of a per
se rule, and remanding for determination by the district court);
                       LANDS COUNCIL v. MARTIN                         2381
Nat’l Audubon, 46 F.3d at 1448 (remanding to the district
court).3

   [4] In conclusion, Plaintiffs have failed to establish an
abuse of discretion requiring reversal of the district court’s
denial of a preliminary injunction relating to Plaintiffs’ NEPA
claims.4

B.    NFMA Claim

   [5] Plaintiffs’ NFMA claim requires us to decide whether
the term “live trees” in the applicable Forest Plan includes all
trees that are not dead. We hold that it does and, therefore,
reverse the district court’s denial of a preliminary injunction
on this ground.

   Amendment 2 of the applicable Forest Plan includes a
series of provisions called the “Eastside Screens,”5 which are
intended to protect old-growth forests. The relevant provision
of the Eastside Screens states that no old-growth “live trees”
of sufficient size may be harvested:

      2) Outside of LOS [late and old structural stages],
      many types of timber sale activities are allowed. The
  3
     The opinion in Smith cited National Audubon Society v. United States
Forest Service, 4 F.3d 832 (9th Cir. 1993). Several months after Smith was
published, the opinion in National Audubon was amended to correct an
unintended typographical error.
   4
     Plaintiffs make several other arguments alleging violations of NEPA
on the merits, but they fail to establish an abuse of discretion by the dis-
trict court. Plaintiffs’ arguments on the merits are not properly before us
on review of a denial of a preliminary injunction. Sw. Voter, 344 F.3d at
918.
   5
     The “Eastside Screens” were originally set forth in the Forest Service’s
“Environmental Assessment for the Continuation of Interim Management
Direction Establishing Riparian, Ecosystem, and Wildlife Standards for
Timber Sales,” Appendix B, June 1995. They have since been appended
to several forest plans, including the Forest Plan that is relevant here.
2382                  LANDS COUNCIL v. MARTIN
      intent is still to maintain and/or enhance LOS com-
      ponents in stands subject to timber harvest as much
      as possible, by adhering to the following standards:

         a) Maintain all remnant late and old seral and/or
      structural live trees ≥ 21” dbh [diameter at breast
      height] that currently exist within stands proposed
      for harvest activities.

Eastside Screens (emphasis added).6

   [6] “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 Forest Service does not
dispute that it is required to comply with the Eastside Screens.
Instead, the Forest Service argues that the Eastside Screens do
not prohibit logging of mortally injured, “dying” trees.7

   The School Fire EIS chose the Scott Mortality Guidelines
as the method of marking trees for harvest. The Scott Mortal-
ity Guidelines are a scientific method of predicting whether
an injured tree is likely to survive beyond a given amount of
time, in this case, one year. Using the Scott Mortality Guide-
lines to select trees for harvest results in the marking of both
dead trees and dying trees, that is, trees that are likely to die
in the relatively near future but that have not yet died. Relying
on the deposition of the Forest Service’s own expert, the dis-
trict court found that some trees that have not yet died have
been marked for harvest in the sales areas. The parties do not
challenge that finding. Accordingly, we must determine
whether the Eastside Screens prohibit logging of dying trees.
  6
    The parties agree that this provision does not apply to the harvesting
of danger trees, which are defined in footnote 1, above.
  7
    The Forest Service also argues that the number of trees marked for har-
vest that could be considered “live” is insignificant. This argument is
beside the point: The Eastside Screens categorically prohibit the harvest-
ing of “live trees.”
                       LANDS COUNCIL v. MARTIN                         2383
  [7] We apply the common meaning of the term “live trees”
because neither the NFMA nor the applicable Forest Plan
defines the term. See Hells Canyon Alliance v. U.S. Forest
Serv., 227 F.3d 1170, 1177 (9th Cir. 2000) (applying the
“common meaning” of terms not defined in the statute). The
common understanding of the term “live” is, quite simply,
“not dead.” See, e.g., Merriam Webster’s Collegiate Dictio-
nary 29, 681 (10th ed. 1993) (defining “live” as “to be alive”
and “alive” as “not dead”). Accordingly, the common mean-
ing of the term “all . . . live trees” is all trees that have not
yet died.

   [8] A contextual clue in the Eastside Screens suggests that
this common meaning was intended. The provision protects
from harvest “all [old-growth] live trees [of a specified mini-
mum size] that currently exist.” Eastside Screens (emphasis
added). The phrase “that currently exist” suggests that even
trees that are expected to die within a year, but that are not
dead, are still “live” because they “currently exist.”8 Applying
this definition, “live trees” will be harvested, which is
expressly prohibited by the Eastside Screens.

  The Forest Service tries to escape this simple formulation
by arguing that the term “live trees” is a technical term under-
  8
    The Forest Service argues that the phrase “currently exist” was
intended instead to make clear that it is permissible to log trees that are
not yet, but would otherwise become, sufficiently large to be covered by
this provision, that is, greater than or equal to 21″ diameter at breast
height. But the phrase “that currently exist” modifies “trees”; for the For-
est Service’s meaning, the provision would say, more properly, “all trees
that currently are ≥ 21” dbh.” Moreover, the Forest Service’s goal is
achieved even without the phrase “that currently exist”: “Maintain all . . .
live trees ≥ 21″ dbh . . . within stands proposed for harvest activities.”
Eastside Screens. Under the Forest Service’s reading, the phrase “that cur-
rently exist” would be superfluous, so we reject that interpretation. See
TRW Inc. v. Andrews, 534 U.S. 19, 31 (2001) (“It is a cardinal principle
of statutory construction that a statute ought, upon the whole, to be so con-
strued that, if it can be prevented, no clause, sentence, or word shall be
superfluous, void, or insignificant.” (internal quotation marks omitted)).
2384                LANDS COUNCIL v. MARTIN
stood by foresters to exclude dying trees and that we must
defer to its technical expertise. We need not decide whether,
in theory, we must employ a technical definition in a Forest
Plan because there is no evidence in this record that the Forest
Service adopted a technical meaning. Not only are the NFMA
and the Forest Plan silent on the definition of “live trees,” but
neither the Forest Service nor Intervenors have cited any
authoritative definition of the term “live trees.” The Forest
Service introduced evidence of a practice of harvesting dying
trees, but that does not establish a technical definition of the
term “live trees.” Foresters very well may consider dying
trees suitable for logging, but on this record we cannot con-
clude that they consider dying trees not “live.” For example,
Intervenors’ expert, on whom the district court relied, testified
that some “live trees” had been designated for removal; in so
testifying, he was applying the common meaning of “live
trees” to include trees that were not dead but that, in his opin-
ion, had a low likelihood of long-term survival. The Forest
Service is free, of course, to amend the Eastside Screens to
allow logging of old-growth dying trees, either by adding a
definition of the term “live trees” or by changing the require-
ment to maintain all live trees of a certain size. Unless and
until it does so, there is no basis to adopt its proposed defini-
tion.

   [9] In summary, the district court made a clear error of law,
and Plaintiffs have established a very strong likelihood of suc-
cess on the merits of their NFMA claim. Additionally, the
resulting injury—logging of old-growth trees—is a permanent
environmental injury. See Amoco Prod. Co. v. Vill. of Gam-
bell, 480 U.S. 531, 545 (1987) (“Environmental injury, by its
nature, can seldom be adequately remedied by money dam-
ages and is often permanent or at least of long duration, i.e.,
irreparable. If such injury is sufficiently likely, therefore, the
balance of harms will usually favor the issuance of an injunc-
tion to protect the environment.”). We therefore reverse the
district court’s denial of a preliminary injunction on the
NFMA claim and remand with instructions to grant immedi-
                    LANDS COUNCIL v. MARTIN                   2385
ately a preliminary injunction to prohibit the logging of any
“live tree” 21″ diameter at breast height that currently exists
in the sales areas—i.e., any tree of the requisite size that is not
yet dead. In accord with the “conservative definition” of a
“live tree” given by Intervenors’ expert, no tree of the requi-
site size with green needles shall be harvested.

  AFFIRMED IN PART, REVERSED IN PART, AND
REMANDED WITH INSTRUCTIONS. Costs on appeal are
awarded to Plaintiffs. The mandate shall issue forthwith.
