Full opinion text
MATHESON, Circuit Judge. TABLE OF CONTENTS I. BACKGROUND 1049 A. Relevant Statutes and Regulations. 1049 1. National Forest Management Act .. 1049 a. The 1982 Rule. 1049 b. The 2005 Rule and the 2005 Modification of the 1982 Rule.. 1050 2. National Environmental Protection Act. 1050 a. The “reasonable range” of alternatives requirement and the “no action” alternative requirement. 1051 b. The “hard look” requirement. 1051 B. Factual and Procedural History. 1052 1. The 1997 Forest Plan: Promulgation, Challenge, and Forest Service Response. 1052 a. Promulgation and Biodiversity’s challenge. 1052 b. Forest Service response: the Chiefs 1999 Decision. 1052 i. NFMA Shortcomings. 1053 1) Insufficient northern goshawk protections. 1053 2) Insufficient snag density. 1053 3) Insufficient objectives for Emphasis Species. 1053 4) Insufficient protections for sensitive plant and animal species. LTD o 1054 ii. NEPA Shortcoming . lO o i — I c. Re-evaluation of the 1997 Forest Plan and the Chiefs interim management instructions. l — l o or ^ 2. Settlement Agreement. 1 — L o cn or 3. Implementation of the Chiefs 1999 Decision and 2000 Settlement Agreement. 1055 a. Phase I Amendment. 1055 b. Phase II Amendment. 1056 4. Biodiversity’s Challenges to the Phase II Amendment 1057 a. Administrative challenges. 1057 b. Wyoming litigation. 1058 c. Colorado litigation. 1058 d. Appeals consolidated. 1058 II. DISCUSSION — WYOMING APPEAL .1058 A. Standing.1059 B. Standard of Review.1059 C. NFMA Issues.1060 1. Regulations Applicable to the Phase II Amendment.1061 2. Biodiversity’s NFMA Challenges to the Phase II Amendment.1061 a. Species viability mandate.1061 i. Viable species mandate under the applicable regulations-1062 1) Interpretation of regulations.1062 a) Whether the regulations have a plain meaning or are ambiguous.1063 b) WTiether the Forest Service’s interpretation is reasonable.1065 i) The Forest Service’s interpretation.1065 ii) Biodiversity’s position.1066 iii) Conclusion.1068 2) Whether the Phase II Amendment fails to meet the species viability mandate under the Forest Service’s interpretation in violation of the APA.1069 ii. Viable species mandate-habitat and protections.1070 1) Northern goshawk.1071 2) Snag-dependent species.1072 3) Sensitive plants.1074 b. Protect RNAs and Botanical Areas.1074 i. Protecting RNAs.1074 ii. Protecting Botanical Areas .1075 c. Suitability and capability assessments.1078 i. When to conduct a suitability or capability analysis .1078 ii. MIS suitability and capability analyses.1080 1) MIS suitability analysis.1080 2) MIS capability analysis.1081 iii. Grazing suitability and capability analyses.1081 1) Grazing suitability analysis.1081 2) Grazing capability analysis.1082 D. NEPA Issues.1083 1. Reasonable Range of Alternatives.1083 2. Hard Look at Sedimentation Policies.1085 3. Hard Look at Historical Grazing Practices.1087 III. DISCUSSION — COLORADO APPEAL.1087 A. Factual and Procedural Background.1088 1. The Settlement Agreement.1088 2. Administrative Challenges to the Phase II Amendment.1088 3. Wyoming Litigation.1089 4. The Motion to Enforce the Settlement Agreement in Colorado and Dismissal Based on Laches.1089 B. Standard of Review and Legal Background.1090 1. Standard of Review.1090 2. Legal Background. 1090 C. Analysis.1092 1. Failure to Consider Laches Is Disfavored.1092 2. Unreasonable Delay.1093 3. Undue Prejudice.1095 IV. CONCLUSION.1096 This appeal consolidates two cases about United States Forest Service (the “Forest Service”) actions in the Black Hills National Forest (“BHNF”), which straddles the Wyoming and South Dakota border. The Appellants, led by Biodiversity Conservation Alliance, are non-profit entities (collectively, “Biodiversity”) interested in species and habitat protection in the BHNF. The Appellees are the Forest Service and several of its officials tasked with managing the BHNF. Intervenors-Appellees are state and county governments and private groups concerned with how management of the BHNF affects nearby private land, state and county citizens, and visitors. Biodiversity sued the Forest Service regarding the BHNF in two separate proceedings. First, in the United States Federal District Court for the District of Wyoming, Biodiversity claimed the Forest Service had failed to comply with various federal statutes and regulations. The court denied Biodiversity’s petition for review. Second, in the United States Federal District Court for the District of Colorado, Biodiversity moved for relief, arguing the Forest Service had violated a settlement agreement. The court dismissed that motion. Biodiversity appeals. Exercising jurisdiction under 28 U.S.C. § 1291, we affirm both the Wyoming and Colorado federal district courts. I. BACKGROUND We describe relevant statutes and regulations, summarize the factual and procedural history of the two cases, and then turn to our analysis. A. Relevant Statutes and Regulations Two sources of statutory and regulatory law govern this case: (1) the National Forest Management Act of 1976 (“NFMA”); (2) the National Environmental Protection Act of 1969 (“NEPA”); and both acts’ implementing regulations. We provide a short overview here and more details during our analysis. 1. National Forest Management Act The Forest Service — a United States Department of Agriculture (“USDA”) agency — manages the national forest system. NFMA requires the Forest Service to manage forests using a two-step process. See 16 U.S.C. §§ 1600-1614. First, the Forest Service must develop a Land and Resource Management Plan (“forest plan”) for each national forest unit. Second, it must implement the forest plan through site-specific projects. 16 U.S.C. § 1604(a) & (i); see also Silverton Snowmobile Club v. USFS, 433 F.3d 772, 785 (10th Cir.2006). Forest plans must “provide for diversity of plant and animal communities based on the suitability and capability of the specific land area-” 16 U.S.C. § 1604(g)(3)(B); see also Utah Envtl. Cong. v. Russell, 518 F.3d 817, 821 (10th Cir.2008). Implementing regulations provide standards and guidelines to create a forest plan and approve any accompanying site-specific projects. See 16 U.S.C. § 1604(g); Utah Envtl. Cong. v. Bosworth, 443 F.3d 732, 737 (10th Cir.2006). When we review a challenge to a forest plan or a site-specific project, we must determine whether the plan or the project meets NFMA and NFMA’s implementing regulations. See Utah Envtl. Cong. v. Troyer, 479 F.3d 1269, 1272 (10th Cir.2007). The NFMA regulations have been amended numerous times. We focus on the 1982 amendment (the “1982 Rule”) and the 2005 amendment (the “2005 Rule”). See 47 Fed.Reg. 43,026 (Sept. 30, 1982) (codified at 36 C.F.R. §§ 219.1-219.29 (1982)); 70 Fed.Reg. 1023 (Jan. 5, 2005) (codified at 36 C.F.R. §§ 219.1-219.16 (2005)). Although more recent rules have superseded both of those rules, the 1982 and 2005 versions are pertinent to this case. a. The 1982 Rule The 1982 Rule required the Forest Service to promote the diversity of species by maintaining “viable populations of existing native and desired” plants and animals. 36 C.F.R. § 219.19 (1982). This “viability mandate” required that each species’ population and habitat be abundant and well-distributed enough to safeguard its continued existence. See id. The 1982 Rule allowed the Forest Service to comply with the viability mandate by monitoring a selected group of “Management Indicator Species” (“MIS”). Id. § 219.19(a)(1). MIS are “[p]lant or animal species ... that are used to monitor the effects of planned management activities on populations of wildlife and fish, including those that are socially or economically important.” Phase II Amendment Glossary, App. at 2338. Thus, the MIS served as proxies for other species’ health in the forest. See 36 C.F.R. § 219.19(a)(1) (1982) (“These species shall be selected because their population changes are believed to indicate the effects of management activities.”); Forest Guardians v. USFS, 641 F.3d 423, 427 (10th Cir.2011) (per curiam) (comparing the MIS to canaries used in coal mines to detect dangerous levels of poisonous gas). In addition to ensuring sufficient habitat for the MIS, the 1982 Rule required the Forest Service to “gather quantitative data on actual MIS populations .... ” See Utah Envtl. Cong. v. Bosworth, 372 F.3d 1219, 1227 (10th Cir.2004). Under the 1982 Rule, the Forest Service measured its success at maintaining “viable populations” of plants and animals in the forest — thereby meeting the NFMA mandate to “provide for diversity” — by monitoring the actual populations of the MIS in the forest. One of the issues in this case is how to interpret and apply § 219.19’s viability mandate. b. The 2005 Rule and the 2005 Modification of the 1982 Rule The Forest Service promulgated several rules that superseded the 1982 Rule. One was the 2005 Rule. See 36 C.F.R. §§ 219.1-219.16 (2005); see also 70 Fed. Reg. 1023 (Jan. 5, 2005) (promulgating the 2005 Rule). But the 1982 Rule survived under certain circumstances. The 2005 Rule permitted the Forest Service to continue using the 1982 Rule for forest plans, such as the BHNF’s, that were already following the 1982 Rule, but with one narrow modification (the “2005 Modification”): “[T]he [Forest Service] may comply with any obligations relating to [MIS] by considering data and analysis relating to habitat unless the plan specifically requires population monitoring or population surveys for the species.” 36 C.F.R. § 219.14(f) (2005). One of the issues in this case is what effect the 2005 Modification had on § 219.19’s viability mandate. 2. National Environmental Protection Act In addition to NFMA, the Forest Service must also comply with NEPA, see 42 U.S.C. §§ 4321-4347. NEPA established a national policy to “promote the understanding of the ecological systems and natural resources important to the United States,” and thereby “reduce or eliminate environmental damage.” Dep’t of Transp. v. Pub. Citizen, 541 U.S. 752, 756, 124 S.Ct. 2204, 159 L.Ed.2d 60 (2004) (quotations omitted). NEPA does not mandate particular results or create substantive limits — rather, it “imposes only procedural requirements on federal agencies with a particular focus on requiring agencies to undertake analyses of the environmental impact of their proposals and actions.” Id. at 756-57, 124 S.Ct. 2204. Broadly speaking, before taking a “major Federal action significantly affecting the quality of the human environment,” 42 U.S.C. § 4332(2)(C), NEPA requires agencies to prepare an environmental impact statement (“EIS”), which determines how much a proposed agency action will affect the environment, 40 C.F.R. § 1502.1-1502.25. Not all agency actions are subject to this requirement—-various regulations “guide federal agencies in determining what actions” must be accompanied by an EIS. Dep’t of Transp., 541 U.S. at 757, 124 S.Ct. 2204; see also 40 C.F.R. §§ 1500.1 to 1508.08. For example, an agency may instead, in certain circumstances, prepare an environmental assessment (“EA”), 40 C.F.R. § 1508.9, which determines whether a proposed action would require a full EIS, 40 C.F.R. § 1501.4(a) & (b), or a categorical exclusion (“CE”), which states the proposed action falls within a category of actions that do not have a significant effect on the environment, 40 C.F.R. § 1508.4. See Utah Envtl. Cong. v. Russell, 518 F.3d at 821. Because a forest plan governs the majority of the Forest Service’s actions in managing a forest, “[t]he creation of a forest plan” and “[a]ny significant amendments” require “the preparation of an EIS.” Silverton Snowmobile Club, 433 F.3d at 785 (quotations omitted). In this appeal we consider an EIS issued as part of a forest plan revision called the “Phase II Amendment.” Especially relevant are two requirements for preparing an EIS: (a) the “no action” alternative and (b) the “hard look.” a. The “reasonable range” of alternatives requirement and the “no action” alternative requirement Under NEPA, an EIS must contain a detailed statement regarding “alternatives to the proposed action.” 42 U.S.C. § 4332(2)(C)(iii). The agency must “[rigorously explore and objectively evaluate all reasonable alternatives” for the proposed action in response to a “specifped] underlying purpose and need.” 40 C.F.R. §§ 1502.13, 1502.14(a). The range of “reasonable alternatives” must at least include the alternative of taking “no action,” 40 C.F.R. § 1502.14(d), which we have described as “the option of taking no new planning action,” New Mexico ex rel. Richardson v. Bureau of Land Mgmt., 565 F.3d 683, 690 (10th Cir.2009). b. The “hard look” requirement An EIS must consider “any adverse environmental effects.” 42 U.S.C. § 4332(2)(C)(iii). This review cannot be superficial—agencies must “take a ‘hard look’ at the environmental consequences of proposed actions utilizing public comment and the best available scientific information.” Colorado Envtl. Coal. v. Dombeck, 185 F.3d 1162, 1171 (10th Cir.1999); see also Robertson v. Methow Valley Citizens Council, 490 U.S. 332, 350, 109 S.Ct. 1835, 104 L.Ed.2d 351 (1989). The “hard look” standard ensures the “agency did a careful job at fact gathering and otherwise supporting its position.” New Mexico ex rel. Richardson, 565 F.3d at 704 (quotations omitted). B. Factual and Procedural History The BHNF covers roughly 1.2 million acres of land straddling the Wyoming and South Dakota border. 2005 Final EIS, App. at 1154-55. Often referred to as “an island in the prairie,” the BHNF features an isolated mountain range surrounded by mid-western prairies. 2005 Final EIS, App. at 1164; see also 1997 Final EIS, App. at 270. The BHNF includes many plants and animals from four ecological zones: the Rocky Mountains, the northern coniferous forests, the eastern hardwood forests, and the mid-western prairies. 1997 Final EIS, App. at 277; 2005 Final EIS, App. at 1164. As a result, the ecological diversity in the area exceeds many other mountain ranges. See 1997 Final EIS, App. at 277. Biodiversity challenges certain Forest Service actions concerning the BHNF. We provide an overview of the facts and procedural background here, and then add details during our analysis. 1. The 1997 Forest Plan: Promulgation, Challenge, and Forest Service Response a. Promulgation and Biodiversity’s challenge After NFMA took effect in 1976, the Forest Service created a forest plan to manage the BHNF and used it for roughly a decade. 1997 Final EIS, App. at 257. In 1992, the Forest Service decided to revise the forest plan. 1997 Final EIS, App. at 260. After years of drafting, surveying, and public notice and comment-making, the Forest Service issued its 1997 Record of Decision, Final EIS, and Revised Forest Plan (collectively, “1997 Forest Plan”). The 1982 Rule governed the preparation of the 1997 Forest Plan. See, e.g., 1997 Record of Decision, App. at 292-93, 298-99, 305. Biodiversity challenged the 1997 Forest Plan in an administrative proceeding, arguing it did not comply with NFMA and NEPA. b. Forest Service response: the Chiefs 1999 Decision In 1999, the Chief of the Forest Service (“Chief’) decided Biodiversity’s administrative appeal (“Chiefs 1999 Decision”). The Chief examined “27 key issues” and determined that, although most of the 1997 Forest Plan complied with NFMA and NEPA, parts of the Plan fell short. Chiefs 1999 Decision, App. at 2462. He identified four “primary deficiencies of concern”: (1) “[v]iability determinations for some species,” (2) “[s]tandards and guidelines to maintain viability of some species,” (3) “[mjanagement indicator species (MIS) requirements,” and (4) “[m]oni-toring direction for some sensitive species.” Id. Within the general framework of those four primary deficiencies, the Chief then discussed more specific shortcomings, including four under NFMA and one under NEPA. i. NFMA Shortcomings 1)Insufficient northern goshawk protections The Chief found the 1997 Forest Plan lacked sufficient objectives to protect northern goshawk populations. Without adequate objectives, such as designating specific areas where goshawks can live after the fledgling stage, the 1997 Forest Plan did not meet NFMA’s viability mandate because the viability of the northern goshawk could not be assessed. Id. at 2507-08. 2) Insufficient snag density The Chief said the 1997 Forest Plan failed to meet NFMA’s requirement to ensure the viability of species because it did not provide enough “snag” habitat. Id. at 2503-05. A “snag” refers to a dead but still-standing tree or portion of a tree. Many species depend on snags for food and shelter. See 2005 Revised Forest Plan Glossary, App. at 2306 (defining “Cavity Nesting Species”), 2363 (defining “Snag”). 3)Insufficient objectives for Emphasis Species The Chief found the 1997 Forest Plan failed to state adequate objectives for certain Emphasis Species. The Forest Service uses the term “Emphasis Species” as an umbrella term encompassing various categories of species that receive particular management attention, including MIS, “Threatened and Endangered Species,” “Sensitive Species,” and “Species of Local Concern.” 2005 Final EIS, App. at 1282. The Chief determined the 1997 Forest Plan did not meet NFMA’s viability mandate because it lacked MIS data, did not adequately explain why it selected certain species for inclusion as MIS, and omitted monitoring objectives. Without the foregoing, the Forest Service could not properly monitor MIS populations. Chiefs 1999 Decision, App. at 2510-12. The Chief also found that without adequate Sensitive Species objectives, the 1997 Forest Plan did not meet NFMA’s viability mandate to ensure Sensitive Species would not decline beyond unrecoverable levels. Id. at 2505-07, 2510-12. 4) Insufficient protections for sensitive plant and animal species Finally, the Chief found the 1997 Forest Plan inadequately protected sensitive “riparian and aquatic species and their habitats in areas with ongoing livestock grazing.” Id. at 2463. The Chief was particularly concerned about the viability of two sensitive snail species and adequately protecting Research Natural Areas (“RNAs”) and Botanical Areas. See id. at 2466-67, 2512-16. The Chief said the Forest Service needed to re-evaluate whether “adequate measures are in place” to protect such species and areas from the deleterious effects of livestock grazing. Id. at 2466. He noted, however, “[w]here existing measures are determined to be adequate, no further actions are required relative to ongoing grazing activities.” Id. For sensitive plants, the Chief said the 1997 Forest Plan did not adequately evaluate the viability of sensitive plant species, properly disclose the indirect and cumulative effects of livestock on sensitive plants, or create adequate methods to mitigate sensitive plant damage from forest management activities such as livestock grazing, noxious weed control, and sedimentation prevention. Id. at 2512-2516. ii. NEPA Shortcoming The Chief found the 1997 Forest Plan did not comply with NEPA’s requirement to take a “hard look” because it made assumptions about ecological impacts and did not properly collect measurements, such as species monitoring and grazing impacts. Id. at 2508-10, 2537. c. Re-evaluation of the 1997 Forest Plan and the Chiefs interim management instructions The Chief affirmed the 1997 Forest Plan only in part and issued instructions to reevaluate and remedy the deficiencies he identified. Id. at 2462, 2521. The Chiefs interim management instructions for the re-evaluation of the 1997 Forest Plan directed the Forest Service to: (1) designate new acreage and protections for northern goshawk habitat, id. at 2464-65, 2523-24; (2) create a minimum density of snags in various areas of the BHNF, id. at 2465-66, 2525-26; (3) conduct further analysis and data collection on all MIS in the BHNF, id. at 2466, 2527; (4) further survey Sensitive Species’ populations and habitats, id. at 2464, 2522-23; and (5) create and implement measures to protect sensitive plants and animals in areas where there was ongoing livestock grazing, id. at 2528. 2. Settlement Agreement When the Chief issued his 1999 Decision, the Forest Service had already spent two years implementing the 1997 Forest Plan in various site-specific projects, some of which Biodiversity administratively challenged — such as a timber sale project in the Beaver Park area of the BHNF. After the Forest Service denied Biodiversity’s Beaver Park administrative challenge, Biodiversity challenged the project’s validity in the Colorado federal district court. Biodiversity argued the Forest Service could not allow the Beaver Park timber sale to proceed because the sale had been authorized under the flawed 1997 Forest Plan. In 2000, Biodiversity and the Forest Service agreed to settle the Beaver Park timber sale litigation. The district court included the settlement agreement (the “Settlement Agreement”) in its dismissal order. Settlement Agreement, App. at 415, 444-47. The Settlement Agreement required the Forest Service to remedy the deficiencies in the 1997 Forest Plan in two phases. During Phase I, the Forest Service would amend the 1997 Forest Plan to incorporate the Chiefs interim management instructions, pending more thorough analysis and re-evaluation of the Plan. Id. at 435-36. During Phase II, the Forest Service would engage in a public notice and comment-making process to amend the 1997 Forest Plan “to ensure compliance with requirements of NFMA, its implementing regulations and agency policy, and all inadequacies identified in the Chiefs [1999 Decision] .... Phase II shall address all of the issues identified in ... this settlement agreement, including northern goshawk, Management Indicator Species, and Research Natural Areas.” Id. at 436. The Phase II Amendment would replace the Phase I Amendment. The Colorado federal district court retained jurisdiction to enforce the Settlement Agreement. Id. at 442. The Settlement Agreement stated it “shall expire ... upon promulgation of the Phase II forest plan amendment, and upon the completion of any additional analysis required by this agreement....” Id. at 443. 3. Implementation of the Chiefs 1999 Decision and 2000 Settlement Agreement a. Phase I Amendment The Forest Service promulgated the Phase I Amendment in May 2001. It incorporated the interim management instructions identified in the Chiefs 1999 Decision and added protections for snags and Sensitive Species. Phase I Amendment Decision Notice and FONSI, App. at 346-48. Biodiversity does not challenge the Phase I Amendment. b. Phase II Amendment During the next four years — 2001 to 2005 — the Forest Service conducted a more thorough analysis of the BHNF to prepare the Phase II Amendment. Also, between 2000 and 2005, several large forest fires burned over 150,000 acres of the BHNF, and between 1997 and 2005, a mountain pine beetle infestation spread from 5,200 to over 100,000 affected acres. 2005 Record of Decision, App. at 1122. As a result, the scope of “the Phase II Amendment was expanded from the original purpose of species viability and RNAs to include fire and insect issues.” Id. at 1122. The Forest Service summarized its Phase II analysis in a Final EIS under NEPA. Id. at 1132. The scope of the Phase II Amendment was to: (1) “[c]ompl[y] with the Chiefs October 1999 [Administrative] Appeal Decision” and correct various deficiencies in the 1997 Forest Plan by ensuring the viability of species, following MIS requirements, and creating monitoring objectives for Sensitive Species; (2) “fulfill[ ] components of the 2000 Settlement Agreement to complete an analysis of candidate RNAs ... and evaluate the viability of MIS and northern goshawk”; and (3) “modify[ ] management direction for fire hazard and insect risk to address both species viability and diversity and effects on resources, human safety, and property.Id. at 1156. The Forest Service considered six alternatives to meet those purposes: (1) re-implement the 1997 Forest Plan, id. at 1133; (2) take “no action” and simply “continue to implement the direction included in the Phase I Amendment,” id.; (3) provide for diversity by emphasizing ideal habitat, id.; (4) focus on creating a dense, mature forest id.; (5) allow timber harvest to equal annual timber growth, id. at 1134; or (6) emphasize “fire and insect hazard reduction,” target “conditions and conservation strategies for species viability,” and establish objectives for ideal habitat (similar to Alternative 3), id. See also id. at 1201-06. The Forest Service examined the pros and cons of each alternative, analyzing how each would affect the various forest ecosystems, id. at 1208-1281; the Emphasis Species, Threatened and Endangered Species, Sensitive Species, and MIS, id. at 1282-1504; Botanical Areas and RNAs, id. at 1520-40; fire hazards and the insect infestations, id. at 1541-75; and livestock grazing, id. at 1591-96. The Forest Service ultimately chose Alternative 6 — which became the Phase II Amendment — as the “environmentally preferred alternative.” Id. at 1136; see also id. at 1122. The Forest Service noted that Alternative 6 would “reduce the incidence of high intensity wildfires and ... reduce the likelihood that endemic insect populations will grow to epidemic levels.” Id. at 1123. This alternative would not eliminate the risks of fire and insect infestation, but it would “minimize negative watershed and wildlife impacts and ... reduce fire suppression costs.” Id. The Forest Service acknowledged Alternative 6 would adversely affect some forest species and explained that “[w]e cannot separate species viability from the effects of fire and insects in the” forest plan. Id. The Forest Service was willing to “accept[ ] small short-term negative effects on fish, wildlife, and plant populations caused by vegetation treatments that reduce forest density” because it believed “these treatments protect and provide habitat needed for long-term viability by reducing susceptibility to damaging fires and insect epidemics.” Id. at 1128. In October 2005, the Forest Service adopted and issued Alternative 6 as the Phase II Amendment, consisting of a 2005 Record of Decision, a 2005 Final EIS, and a 2005 Revised Forest Plan. 4. Biodiversity’s Challenges to the Phase II Amendment a. Administrative challenges In 2006, Biodiversity challenged the Phase II Amendment, arguing it fails to comply with NFMA, the 1982 Rule, NEPA, the Chiefs 1999 Decision, and the Settlement Agreement. In November 2006, the Chief upheld the Phase II Amendment (“Chiefs 2006 Decision”). Chiefs 2006 Decision, App. at 2698. In separate administrative cases, Biodiversity also challenged nine site-specific projects that the Forest Service had implemented under the Phase II Amendment. Biodiversity argued the projects violate NFMA, the 1982 Rule, NEPA, the Chiefs 1999 Decision, and the Settlement Agreement. The Chief denied all nine challenges, including the first site-specific challenge to the Dean Project in August 2006. Dean Timber Sale Decision, App. at 3883, 3886. In January 2011, the Chief denied the last site-specific challenge to the Mystic Range Project. Mystic Allotment Decision, App. at 4629-30. b. Wyoming litigation In October 2011, Biodiversity petitioned for review of agency action in the Wyoming federal district court under the Administrative Procedure Act, 5 U.S.C. § 706(2)(A) & (D). Pet. for Review, App. at 25, 31. Biodiversity argued the Forest Service’s actions promulgating the Phase II Amendment and implementing the accompanying nine site-specific projects were arbitrary, capricious, an abuse of discretion, and otherwise not in accordance with NFMA, the 1982 Rule, NEPA, the Chiefs 1999 Decision, and the 2000 Settlement Agreement. Biodiversity’s petition mentioned the nine site-specific projects but did not craft individualized arguments against them. See Pet. for Review, App. at 26-27, 30-31. In November 2012, the district court upheld the Forest Service’s actions. It denied a motion for reconsideration in April 2013. Biodiversity timely appealed (Case No. 13-8053). c. Colorado litigation In the meantime, the Beaver Park litigation that Biodiversity filed in 1999 in the Colorado federal district court lay dormant. After its defeat in Wyoming, Biodiversity attempted in May 2013 to reopen the Colorado case by moving to enforce the Settlement Agreement and compel the Forest Service to prepare a Phase II Amendment that would comply with NFMA, the 1982 Rule, the Chiefs 1999 Decision, and the Settlement Agreement. Relying on laches, the district court denied the motion, reasoning that Biodiversity had waited too long to enforce its rights under the Settlement Agreement. Biodiversity timely appealed (Case No. 13-1352). d.Appeals consolidated Biodiversity moved to consolidate the two appeals. The Forest Service did not object. We granted the motion because the cases “involve a common nucleus of facts and similarity of legal issues.... ” Order at 2, Biodiversity v. USFS, Nos. 13-1352 & 13-8053, (10th Cir. Sep. 3, 2013), ECF No. 10104703. II. DISCUSSION — WYOMING APPEAL Because NFMA and NEPA do not provide a private right of action, we review Biodiversity’s challenges to the Phase II Amendment and the nine site-specific projects as final agency actions under the Administrative Procedure Act (“APA”). Utah Envtl. Cong. v. Bosworth, 443 F.3d 732, 739 (10th Cir.2006). We first address Biodiversity’s standing and our standard of review. We then address Biodiversity’s arguments challenging the Forest Service’s actions under NFMA and NEPA. A. Standing We agree with the district court that the uncontested declarations submitted by individual members of each of the Biodiversity plaintiffs were sufficient to establish Article III standing. They stated aesthetic and recreational injuries caused by the Forest Service’s Phase II Amendment and redressable through this lawsuit. See Friends of the Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 528 U.S. 167, 180, 120 S.Ct. 693, 145 L.Ed.2d 610 (2000) (“[T]o satisfy Article Ill’s standing requirements, a plaintiff must show (1) it has suffered an ‘injury in fact’ that is (a) concrete and particularized and (b) actual or imminent, not conjectural or hypothetical; (2) the injury is fairly traceable to the challenged action of the defendant; and (3) it is likely, as opposed to merely speculative, that the injury will be redressed by a favorable decision.”) (citing Lujan v. Defenders of Wildlife, 504 U.S. 555, 560-61, 112 S.Ct. 2130, 119 L.Ed.2d 351 (1992)). B. Standard of Review The standard of review for Biodiversity’s NFMA and NEPA claims is the same because we consider them both under the APA. We review de novo a district court’s decision in an APA case. Utah Envtl. Cong. v. Bosworth, 443 F.3d at 739. Under the APA, any “person suffering legal wrong because of agency action, or adversely affected or aggrieved by agency action within the meaning of a relevant statute, is entitled to judicial review thereof.” 5 U.S.C. § 702. The reviewing court shall set aside the agency action under § 706(2) if it is: (A) arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law; (B) contrary to constitutional right, power, privilege, or immunity; (C) in excess of statutory jurisdiction, authority, or limitations, or short of statutory right; (D) without observance of procedure required by law; (E) unsupported by substantial evidence ...; or (F) unwarranted by the facts to the extent [they] are subject to trial de novo by the reviewing court. Id. § 706(2); see also Citizens to Preserve Overton Park, Inc. v. Volpe, 401 U.S. 402, 414, 91 S.Ct. 814, 28 L.Ed.2d 136 (1971). In this appeal, Biodiversity relies on § 706(2)(A), arguing the agency’s action was arbitrary and capricious. See Aplt. Br. at 19. Under § 706(2)(A), an agency’s action is “arbitrary and capricious ‘if the agency ... entirely failed to consider an important aspect of the problem, offered an explanation for its decision that runs counter to the evidence before the agency, or is so implausible that it could not be ascribed to a difference in view or the product of agency expertise.’ ” Utah Envtl. Cong. v. Bosworth, 443 F.3d at 739 (quoting Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43, 103 S.Ct. 2856, 77 L.Ed.2d 443 (1983)). Likewise, an agency’s decision is arbitrary and capricious if the agency failed to base its decision on “consideration of the relevant factors,” or if “there has been a clear error of judgment” on the agency’s part. Id. “When courts consider such challenges, an agency’s decision is entitled to a presumption of regularity, and the challenger bears the burden of persuasion.” San Juan Citizens Alliance v. Stiles, 654 F.3d 1038, 1045 (10th Cir.2011) (citations omitted). Our deferential review “is especially strong where the challenged decisions involve technical or scientific matters within the agency’s area of expertise.” Utah Envtl. Cong. v. Russell, 518 F.3d 817, 824 (10th Cir.2008) (citing Marsh v. Or. Natural Res. Council, 490 U.S. 360, 378, 109 S.Ct. 1851, 104 L.Ed.2d 377 (1989)); see also San Juan Citizens, 654 F.3d at 1045 (“[W]hen specialists express conflicting views, an agency must have discretion to rely on the reasonable opinion of its own qualified experts, even if, as an original matter, a court might find contrary views more persuasive.” (quotations omitted)). Sometimes, as here, a plaintiff will also challenge the agency’s interpretation of the applicable regulations. We must determine which interpretation to judge the agency’s action against. In making this determination, we give “substantial deference” to the agency’s interpretation of its own regulations. Utah Envtl. Cong. v. Troyer, 479 F.3d 1269, 1281 (10th Cir.2007) (“We may reject the agency’s interpretation only when it is unreasonable, plainly erroneous, or inconsistent with the regulation’s plain meaning.” (quotations omitted)). Although deferential, our inquiry must “be searching and careful.” Ecology Ctr., Inc. v. USFS, 451 F.3d 1183, 1188 (10th Cir.2006) (quotations omitted). We will not, for example, accept appellate counsel’s post-hoc rationalizations for agency action — we must uphold the agency’s action “if at all, on the basis articulated by the agency itself.” Colo. Wild, Heartwood v. USFS, 435 F.3d 1204, 1213 (10th Cir.2006) (quoting Motor Vehicle Mfrs., 463 U.S. at 50, 103 S.Ct. 2856). C. NFMA Issues To address Biodiversity’s claim that the Phase II Amendment violates NFMA, we first determine (1) which regulations apply to the Phase II Amendment. We then analyze (2) whether the Phase II Amendment fails to: (a) comply with the viability mandate of the 1982 Rule; (b) adequately protect RNAs and Botanical Areas; or (c) conduct a proper suitability and capability analysis for MIS and livestock grazing. 1. Regulations Applicable to the Phase II Amendment NFMA regulations govern preparation of forest plans. 16 U.S.C. § 1604(a) & (g); Silverton Snowmobile Club v. USFS, 438 F.3d 772, 785 (10th Cir.2006). Forest plans and their amendments typically must comply with the regulation in place at the time the plan or amendment is final. Ecology Ctr., 451 F.3d at 1191. Because the Forest Service issued the Phase II Amendment after the 2005 Rule was in place, it would normally need to comply with that rule. But a transition provision in the 2005 Rule allowed the Forest Service to amend the 1997 Forest Plan based on the superseded 1982 Rule. See 36 C.F.R. § 219.14(b) & (e) (2005); see also Forest Guardians v. USFS, 495 F.3d 1162, 1168 (10th Cir.2007) (“Forest plans may require particular standards to be followed regardless of later changes in the regulations.” (quotations omitted)). The Phase II Amendment repeatedly states it is based on the 1982 Rule and the 2005 Modification codified in § 219.14(f). See, e.g., 2005 Record of Decision, App. at 1141 (“The Phase II Amendment is done under the provisions of the former 1982 NFMA planning rule as modified by 36 CFR 219.14(f).”); see also id. at 1122 (same); 2005 Final EIS, App. at 1150, 1441 (same); 2005 Revised Forest Plan, App. at 2039, 2102 (same). The Forest Chief recognized this in his 2006 decision denying Biodiversity’s challenge to the Phase II Amendment. See Chiefs 2006 Decision, App. at 2698-99 & n.l. So does Biodiversity. Aplt. Br. at 29; 33, 35; Aplt. Reply Br. at 1-5. Although the Forest Service describes the rules applicable to the Phase II Amendment differently in its brief, see Aplee. Br. at 22-24, 29, we do not see how the agency can vary from what is clearly stated in the Phase II Amendment itself. We therefore evaluate the Phase II Amendment using the 1982 Rule as modified by the 2005 Modification. The parties debate how these rules should be interpreted and applied, in particular what the regulations require the Forest Service to do to ensure species viability. 2. Biodiversity’s NFMA Challenges to the Phase II Amendment a. Species viability mandate Biodiversity argues the Phase II Amendment fails to comply with the 1982 Rule’s “viability mandate” in § 219.19. The 1982 Rule required the Forest Service to “maintain viable populations” of plants and animals in the BHNF. 36 C.F.R. § 219.19 (1982). Section 219.19 provided, in relevant part: “to insure that viable populations will be maintained, habitat must be provided to support, at least, a minimum number of reproductive individuals and that habitat must be well distributed so that those individuals can interact with others in the planning area.” 36 C.F.R. § 219.19 (1982). Section 219.19 also specifically required the Forest Service to collect population data on MIS. See id. § 219.19(a), (a)(1), (a)(2), and (a)(6). We have recognized § 219.19 used MIS to “measure the impact of habitat changes on the Forest’s diversity.” Utah Envtl. Cong. v. Bosworth, 372 F.3d 1219, 1226 (10th Cir.2004) (quotations omitted). MIS therefore served under § 219.19 as “a bellwether for other species.... ” Forest Guardians v. USFS, 641 F.3d 423, 427 (10th Cir.2011) (per curiam) (quotations omitted). Section 219.14(f) of the 2005 Rule — the 2005 Modification — allowed the Forest Service to “comply with any obligations relating to [MIS] by considering data and analysis relating to habitat....” 36 C.F.R. § 219.14(f) (2005). Biodiversity claims the Forest Service violated § 219.19’s “viability mandate” in failing to: (i) conduct adequate viability analyses to ensure the viability of species; and (ii) provide sufficient habitat and protections in the Phase II Amendment to ensure the viability of northern goshawk, snag-dependent species, and sensitive plants. i. Viable species mandate under the applicable regulations Biodiversity claims the Phase II Amendment fails to comply with § 219.19’s viability mandate and the 2005 Modification because the Forest Service did not collect or consider enough population data or create adequate population objectives to ensure the viability of species. As stated above, under the APA, Biodiversity must show the Forest Service acted arbitrarily and capriciously under the applicable regulations. 1) Interpretation of regulations Biodiversity and the Forest Service disagree about how to interpret the applicable regulations regarding species viability. We must assess this interpretation issue before we proceed to consider the merits of Biodiversity’s APA challenge. Using familiar rules of construction, see Jicarilla Apache Tribe v. Andrus, 687 F.2d 1324, 1332 (10th Cir.1982) (“Regulations are generally subject to the same rules of construction as statutes.”), we first “determine whether the language at issue has a plain and unambiguous meaning with regard to the particular dispute in the case,” Robinson v. Shell Oil Co., 519 U.S. 337, 340, 117 S.Ct. 843, 136 L.Ed.2d 808 (1997). If the meaning is plain, it controls. Id. If the meaning is ambiguous, we defer “to an agency’s interpretation of its own ambiguous regulation, even when that interpretation is advanced in a legal brief,” Christopher v. SmithKline Beecham Corp., — U.S. -, 132 S.Ct. 2156, 2166, 183 L.Ed.2d 153 (2012) (citing Auer v. Robbins, 519 U.S. 452, 117 S.Ct. 905, 137 L.Ed.2d 79 (1997)), unless the agency’s interpretation is “plainly erroneous or inconsistent with the regulation,” id. (quotations omitted); see also Utah Envtl. Cong. v. Troyer, 479 F.3d 1269, 1281 (10th Cir.2007) (stating we reject Auer deference when the agency’s interpretation is “unreasonable”). In other words, we “accord Auer deference to the [agency’s] interpretation” when we determine it “is a reasonable interpretation of its own regulation.” Decker v. Nw. Envtl. Def. Ctr., — U.S. -, 133 S.Ct. 1326, 1331, 1337, 185 L.Ed.2d 447 (2013). “[A]n agency’s interpretation need not be the only possible reading of a regulation — or even the best one — to prevail.” Id. at 1337. Biodiversity contends § 219.19’s “plain language” defines viable species in terms of “minimum number of individuals.” Aplt. Br. at 30-31 (emphasis in original). But beyond that, Biodiversity fails to explain whether its interpretation of the species viability mandate to collect or consider population data or create population objectives is based on the plain meaning of § 219.19 or a reasonable reading of the regulation’s ambiguous terms, nor does Biodiversity address whether § 219.14(f) has a plain meaning. The Forest Service likewise does not clearly specify whether its interpretation is based on the regulations’ plain meaning. If we find the regulations’ language is not plain and the Forest Service’s interpretation of the ambiguous regulations is reasonable, we must defer to that interpretation. To determine which interpretation of the regulations applies to Biodiversity's APA challenge, we a) address whether the plain meaning of the regulations requires the Forest Service to collect or consider population data or create population objectives to comply with the viability mandate. We conclude the regulations are ambiguous on this score. We then b) examine whether the Forest Service’s interpretation is reasonable. We conclude that it is and therefore entitled to Auer deference. Biodiversity’s interpretation does not convince us otherwise. a) Whether the regulations have a plain meaning or are ambiguous The parties have framed the issue as whether § 219.19 of the 1982 Rule and § 219.14(f) of the 2005 Rule imposed a duty on the Forest Service to collect or consider population data or create population objectives to ensure the viability of species. We must determine (1) whether § 219.19’s viability mandate plainly states that population data must be collected or considered or that population objectives must be created, and for which species, and (2) whether § 219.14(f) unambiguously states how it affects the MIS obligations created by § 219.19. First, as to § 219.19, we find it does not clearly state whether and to what extent the viability mandate requires more than providing and managing habitat to ensure species viability. It states, in relevant part: Fish and wildlife habitat shall be managed to maintain viable populations of existing native and desired non-native vertebrate species in the planning area. For planning purposes, a viable population shall be regarded as one which has the estimated numbers and distribution of reproductive individuals to insure its continued existence is well distributed in the planning area. In order to insure that viable populations will be maintained, habitat must be provided to support, at least, a minimum number of reproductive individuals and that habitat must be well distributed so that those individuals can interact with others in the planning area. 36 C.F.R. § 219.19 (1982). The 1982 Rule mandates that “habitat shall be managed to maintain viable populations of existing native and desired” plants and animals. Id. It defines “viable population” as “one which has the estimated numbers and distribution of reproductive individuals to insure its continued existence is well distributed in the planning area.” Id. And it requires “habitat must be provided to support, at least, a minimum number of reproductive individuals and that habitat must be well distributed” to ensure a viable population. Id. Although § 219.19 states the Forest Service must provide and manage habitat to ensure viable species, the text does not clearly state whether and to what extent collecting or considering population data was necessary. The regulation speaks of the habitat responsibility using terms such as “estimated numbers,” “distribution of reproductive individuals,” and “minimum number.” Id. Although that language may reasonably be read as having imposed a population data requirement, these references do not plainly direct the Forest Service to collect or consider population data or create population objectives. For example, § 219.19’s requirement that “habitat shall be managed to maintain viable populations,” does not prescribe how to achieve “viable populations” — whether through habitat management, population data, or both. And even if we were to read § 219.19 to include a population data requirement, the regulation says nothing about what and how much data must be collected, how such data must be analyzed, and which species must be included. We conclude § 219.19 is ambiguous as to whether and to what extent the Forest Service must collect and consider population data or create population objectives to ensure the viability of species. Second, the effect of § 219.14(f) of the 2005 Modification also is not plain. Regarding MIS, § 219.19 of the 1982 Rule states, in relevant part: (a) Each alternative shall establish objectives for the maintenance and improvement of habitat for management indicator species selected under paragraph (g)(1) of this section, to the degree consistent with overall multiple use objectives of the alternative. To meet this goal, management planning for the fish and wildlife resource shall meet the requirements set forth in paragraphs (a)(1) through (a)(7) of this section. (a)(1) In order to estimate the effects of each alternative on fish and wildlife populations, certain vertebrate and/or invertebrate species present in the area shall be identified and selected as management indicator species and the reasons for their selection will be stated. These species shall be selected because their population changes are believed to indicate the effects of management activities .... (a)(2) Planning alternatives shall be stated and evaluated in terms of both amount and quality of habitat and of animal population trends of the management indicator species. [* * *] (a)(6) Population trends of the management indicator species will be monitored and relationships to habitat changes determined.... 36 C.F.R. § 219.19 (1982). Thus, § 219.19 requires the Forest Service to select MIS, “monitor[ ]” the MIS “[population trends,” and “evaluate[]” the population data “to estimate the effects” of forest management on the other species in the forest. 36 C.F.R. § 219.19(a), (a)(1), (a)(2), & (a)(6) (1982). Accordingly, we have held that for MIS, § 219.19 of the 1982 Rule requires the Forest Service to “monitor” population data. See Utah Envtl. Cong. v. Bosworth, 372 F.3d 1219, 1226 (10th Cir.2004) (“Plainly the regulations require that the Forest Service monitor population trends of the MIS in order to evaluate the effects of forest management activities on the MIS and the viability of desired fish and wildlife populations in the forest more generally.”). The 2005 Modification, however, created new options for the Forest Service as to MIS. It states: Management indicator species. For units with plans developed, amended, or revised using the provisions of the planning rule in effect prior to November 9, 2000 [i.e., the 1982 Rule], the Responsible Official may comply with any obligations relating to [MIS] by considering data and analysis relating to habitat unless the plan specifically requires population monitoring or population surveys for the species. Site-specific monitoring or surveying of a proposed project or activity area is not required, but may be conducted at the discretion of the Responsible Official. 36 C.F.R. § 219.14(f) (2005); see also 70 Fed.Reg. 1023, 1052 (Jan. 5, 2005) (promulgating the 2005 Rule and explaining “ § 219.14(f) provides that MIS obligations may be met by considering data and analysis relating to habitat”). The 2005 Modification authorizes the Forest Service to “comply with any obligations” relating to MIS by “considering data and analysis relating to habitat.” 36 C.F.R. § 219.14(f) (2005). The phrase “any obligations” connotes a broad scope, including possibly every MIS obligation imposed by § 219.19. But even the word “any” may not be plain depending on the regulatory context. See Christopher v. SmithKline Beecham Corp., — U.S. -, 132 S.Ct. 2156, 2170, 183 L.Ed.2d 153 (2012) (“We have recognized that the modifier ‘any’ can mean different things depending upon the setting....” (quotations omitted)). And as noted above, § 219.19 is ambiguous as to what “obligations” it creates for MIS beyond monitoring. In the NFMA and 1982 Rule context, “any obligations relating to [MIS]” could refer only to MIS monitoring obligations contained in § 219.19(a), (a)(1), (a)(2), & (a)(6), or could include additional obligations arising from the species viability mandate. Section 219.14(f) is not clear as to whether it completely obviates all possible MIS obligations imposed in § 219.19 — including obligations due to the general species viability mandate — or only MIS monitoring obligations. Accordingly, as to whether and what extent § 219.19 required the Forest Service to collect and consider population data or create population objectives to meet the species viability mandate, and the extent to which § 219.14(f) supplanted the Forest Service’s MIS responsibilities in § 219.19, we conclude the regulations do not convey a plain meaning and therefore are ambiguous. b) Whether the Forest Service’s interpretation is reasonable Because the regulations’ meaning is not plain as to a population data requirement, we defer to the Forest Service’s interpretation if it is reasonable or unless it is plainly erroneous or inconsistent with the regulation. See Auer, 519 U.S. at 461, 117 S.Ct. 905. We first i) examine the Forest Service’s interpretation and conclude it is reasonable. We then ii) consider Biodiversity’s position, concluding that although Biodiversity advances a competing interpretation, it has not convinced us the Forest Service’s interpretation should not be entitled to Auer deference. We accordingly iii) defer to the Forest Service’s interpretation of the regulations concerning a population data requirement. i) The Forest Service’s interpretation The Forest Service’s interpretation of § 219.19’s viability mandate and the 2005 Modification distinguishes MIS and non-MIS. Regarding MIS, the Forest Service acknowledges that before the 2005 Rule, § 219.19 of the 1982 Rule required it to “monitor the population trends” of MIS. Aplee. Br. at 24 (quotations omitted). But the Forest Service contends that § 219.14(f) of the 2005 Rule — the 2005 Modification — made compliance “ “with any obligations relating to management indicator species’ ” in the 1982 Rule optional so long as it “ ‘considered] data and analysis relating to habitat...Aplee. Br. at 23 (quoting 36 C.F.R. § 219.14(f) (2005)). The Forest Service contends its reliance on the 2005 Modification obviates “any” requirement in the 1982 Rule to use MIS population data to ensure species viability in the Phase II Amendment. See id. at 25. Regarding non-MIS, the Forest Service indicates in its brief that the 2005 Modification relieved it of whatever population data gathering obligations arose under the 1982 Rule. See Aplee. Br. at 29 (“Because the Forest Service properly relied on the 2005 [R]ule in developing the Phase II [Amendment], Biodiversity’s argument concerning the need for population data under the 1982 Rule fails.”). The Forest Service clarified its position at oral argument: It’s one thing to look at application of the '82 Rules as interpreted by this court with reference to monitoring to MIS and to talk about population data because they are selected species. But more broadly, as the district court noted there is no decision by this court or any other court that says for non-MIS species you’ve got to maintain population data.... The Forest Service has never believed it had that obligation [to collect non-MIS data].... That obligation doesn’t exist. Oral Arg. at 15:29-15:53, 16:27-16:30, 16:47-16:50. In response to the court’s question, “beyond MIS, is the Forest Service obligated to count any species?,” id. at 18:28-18:34, counsel for the Forest Service replied, “I would say there is no general obligation to do so,” id. at 18:37-18:45. The Forest Chief took this position in his 2006 Decision denying Biodiversity’s administrative appeal. See Chiefs 2006 Decision, App. at 2708-10 (rejecting Biodiversity’s argument that the 1982 Rule obligated the Forest Service to collect and consider population data, or estimate the minimum number of individuals to maintain a viable population, in part, because “[t]here is no policy or regulatory requirement for the [BH]NF to propose or establish minimum viable population numbers for any of the species that occur within the planning area”). At least two circuits agree with the Forest Service regarding the non-MIS. See Sierra Club v. Martin, 168 F.3d 1, 7 (11th Cir.1999) (rejecting an argument which interpreted § 219.19 to require collecting data on all species because it would make nonsensical the regulation’s requirement to collect data on MIS); Inland Empire Pub. Lands Council v. USFS, 88 F.3d 754, 758, 761-62 & n. 8 (9th Cir.1996) (concluding the Forest Service’ habitat analysis of seven non-MIS Sensitive Species did not violate § 219.19’s viability mandate). In sum, the Forest Service interprets the regulations narrowly to mean that § 219.19 of the 1982 Rule obligated the Forest Service to ensure the viability of species but imposed no duty to use population data other than the MIS monitoring obligations, and the 2005 Modification relieved the Forest Service of “any” MIS monitoring obligation. ii) Biodiversity’s position Biodiversity attempts to challenge the Forest Service’s interpretation of the regulations by positing its own competing interpretation. We are bound to defer to the Forest Service’s interpretation, however, unless it is “unreasonable, plainly erroneous, or inconsistent with the regulation’s plain meaning.” Troyer, 479 F.3d at 1281 (quotations omitted). Indeed, “[a]n agency’s interpretation need not be the only possible reading of a regulation — or even the best one — to prevail.” Decker, 133 S.Ct. at 1337. Accordingly, Biodiversity cannot succeed in challenging the Forest Service’s interpretation merely by proposing another interpretation, no matter how reasonable. It must instead convince us that the Forest Service’s interpretation is unreasonable or plainly erroneous — which Biodiversity does not even attempt to do. In any case, Biodiversity has not advanced a persuasive alternative interpretation to the Forest Service’s. Biodiversity observes the 1982 Rule required the Forest Service to “ensure viable populations of all native species under § 219.19,” Aplt. Br. at 25, and “define[d] viability in terms of a minimum number of individuals,” id. at 31 (emphasis in original). “As such, numerical data is relevant and applicable to viability determinations.... ” Id. at 31. Biodiversity further contends the 2005 Modification— § 219.14(f) — addressed “MIS monitoring compliance, not viability determinations.... ” Aplt. Br. at 33. Biodiversity stresses the difference between MIS monitoring and maintaining viable species and argues the Forest Service conflates the two. See Aplt. Reply Br. at 2-3. Although the 2005 Modification “eliminated the 1982 [RJule’s requirement to monitor MIS population trends, it did not eliminate the definition of a viable population,” id. at 6, nor did it “eliminate the relevance, importance and applicability of population figures and estimates for species viability determinations and maintenance,” id. at 7. Biodiversity therefore generally argues the Forest Service must do more than habitat analysis to ensure species viability. But beyond that, Biodiversity’s interpretation of the regulations is difficult to decipher. Biodiversity’s various arguments can be read to suggest a population data requirement applied to: (1) all species; (2) some species beyond Emphasis Species; (3) species “requiring special attention;” (4) all Emphasis Species; (5) some Emphasis Species; (6) some or all Sensitive Species; (7) perhaps Species of Local Concern; (8) and MIS to the extent § 219.19 imposed population data duties beyond MIS monitoring. Compounding this problem is Biodiversity’s failure to specify what population data must be collected, how it must be analyzed, and whether it must be collected at all when the Forest Service’s habitat analysis for a particular species may be adequate to ensure species viability. We will not attempt to bring cohesion to Biodiversity’s interpretation(s). Perry v. Woodward, 199 F.3d 1126, 1141 n. 13 (10th Cir.1999) (declining to address an alternative argument because defendants “have not adequately developed the argument,” and “[t]his court ... will not craft a party’s arguments for him”). iii) Conclusion Having reviewed the parties’ interpretations of the regulations, we conclude the Forest Service’s interpretation is narrow but not unreasonable. It allows the agency flexibility to use population data, as it has done, in meeting the species viability requirement, and finds support in Ninth and Eleventh Circuit precedent. Biodiversity has not persuaded us otherwise, presenting its interpretation in various permutations, leaving us to guess what it is and without any basis to conclude the Forest Service’s interpretation is plainly erroneous, inconsistent with the regulations, or otherwise unreasonable. For the foregoing reasons, we must defer in these circumstances to the Forest Service’s interpretation of § 219.19 of the 1982 Rule and § 219.14(f) of the 2005 Rule and proceed to our analysis of Biodiversity’s challenge to the Phase II Amendment’s compliance with the species viability mandate. 2) Whether the Phase II Amendment fails to meet the species viability mandate under the Forest Service’s interpretation in violation of the APA In light of the preceding analysis, to succeed on its APA claim Biodiversity must show the Forest Service failed to comply with its own interpretation of § 219.19’s viability mandate and the 2005 Modification in violation of the APA. Biodiversity fails to do so. Biodiversity contends the Phase II Amendment fails to ensure “species viability as required by § 219.19.” Aplt. Br. at 30. Referring to nine MIS and eight non-MIS Emphasis Species as examples, it argues the Forest Service did not properly use population data for those species. Aplt. Br. at 30-35; Aplt. Reply Br. at 11-17. As to non-MIS, § 219.19 imposed no obligation to use population data under the Forest Service’s interpretation. As to MIS, the Forest Service conducted habitat viability analyses. Biodiversity faults the Forest Service for failing to use population data for MIS. But under the Forest Service’s interpretation of the 2005 Modification, the Phase II Amendment may comply with “any” MIS monitoring obligations imposed under § 219.19 by using habitat data and analysis in lieu of population data. See 36 C.F.R. § 219.14(f) (2005). Biodiversity fails to show how the Phase II Amendment is deficient under the Forest Service’s interpretation of § 219.19’s viability mandate and the 2005 Modification