The Center for Biological Diversity, the Western Land Exchange Project, and the Sierra Club (collectively, “Appellants”) bring suit against Asarco LLC (“Asarco”), a mining company, and the Department of Interior and the Bureau of Land Management (collectively, “BLM”). Appellants contend that the BLM’s approval of a land exchange violates the National Environmental Policy Act (“NEPA”), 42 U.S.C. §§ 4321-70; the Federal Land Policy and Management Act (“FLPMA”), 43 U.S.C. §§ 1701-87; and the Mining Law of 1872, 30 U.S.C. §§ 21-54.
If the proposed exchange occurs, Asarco would take fee simple ownership of the land. In that event, Asareo’s use of the land would not be subject to the requirements of the Mining Law of 1872.
If the proposed exchange does not occur, the land will continue to be owned by the United States. In that event, Asarco would not be permitted to conduct mining operations on the land unless it complies with the Mining Law of 1872. Specifically, Asarco could not conduct a new mining operation on the land without first submitting a Mining Plan of Operations (“MPO”) to the BLM. The MPO would have to include detailed information about the operations, management, monitoring, and environmental impacts of the proposed mining activities. The BLM would then have to approve the MPO before the new mining could proceed.
As part of the process of approving the land exchange, the BLM prepared a Final Environmental Impact Statement (“FEIS”) pursuant to NEPA. In the FEIS, the BLM assumed that Asarco would carry out mining operations on the land in the same manner whether or not the land exchange occurred. Because of this assumption, the FEIS contains no comparative analysis of the environmental consequences for the different alternatives proposed. The BLM made the same assumption in its Record of Decision (“ROD”) approving the land exchange. The ROD, like the FEIS, contains no analysis of how the environmental consequences — and the implications for the public interest — would differ depending on whether the proposed land exchange occurs.
Because the BLM has conducted no comparative analysis, we hold that it has not “taken a ‘hard look’ at the environmental consequences of its proposed action” in violation of NEPA, Blue Mountains Biodiversity Project v. Blackwood, 161 F.3d 1208, 1211 (9th Cir.1998), and that its approval of the proposed land exchange was “arbitrary and capricious” in violation of FLPMA. Webb v. Lujan, 960 F.2d 89, 91 (9th Cir.1992). We reverse the decision of the district court approving the actions of the BLM.
I. Background
Asarco owns and operates the Ray Mine complex in Gila and Pinal Counties, Arizona. The complex includes a 265,000 ton-*1066per-day open pit copper mine, a copper smelter with an acid plant, solution extraction/electrowinning plants, mills, concentrators, leaching systems, and related support facilities. Ore from the mine is transported eighteen miles to the Hayden Smelter for processing. In 1996, the complex produced 430 million pounds of copper anodes, over 70 million pounds of copper cathodes, 1.3 million ounces of silver in concentrate, and 623,000 tons of sulfuric acid. The Ray Mine is the second most productive copper mine in Arizona and the third most productive copper mine in the United States.
In 1994, Asarco proposed a land exchange with the BLM in order to consolidate its holdings and to support and expand its mining operations at the complex. As amended in 1997, the proposed land exchange would convey to Asarco in fee simple thirty-one parcels of public land totaling 10,976 acres (the “selected lands”). In return, Asarco would convey to the BLM eighteen parcels of private land totaling roughly 7,300 acres (the “offered lands”). FLPMA authorizes the Secretary of Interior to approve land exchanges. 43 U.S.C. § 1716.
The United States owns and the BLM administers as full estates 8,196 acres of the selected lands. The remaining 2,780 acres of the selected lands are owned and administered as “split estates.” Asarco owns or is purchasing, in transactions not at issue in this appeal, the surface estate of these lands, while the United States owns and the BLM administers the mineral estate. Twenty-three of the thirty-one parcels of selected lands are located near the Ray Mine and the community of Ray, Arizona. Five of the parcels are located twelve to fifteen miles southeast of the Ray Mine, near the communities of Hayden and Winkleman, Arizona. The remaining three parcels are located about 50 miles west of the Ray Mine near the community of Casa Grande, Arizona.
The selected lands provide important wildlife and plant habitat, including high priority reintroduction habitat for desert bighorn sheep, 6,860 acres of endangered desert tortoise habitat, and potential habitat for threatened and endangered birds. Upland plant communities cover 99.2% of the selected lands and include riparian plant communities and three plant species designated for special status by the BLM. Some of the selected lands are immediately adjacent to the White Canyon Area of Critical Environmental Concern, and some are adjacent to or in close proximity to the White Canyon Wilderness. The selected lands include seventy-eight archaeological sites, of which forty are regarded as eligible for nomination to the National Register of Historic Places.
Asarco and the BLM are forthright in stating that they foresee the following five uses for the selected lands following the land exchange. These uses are described with specified acreage in the FEIS as follows:
(1) Existing mining: 272 acres (2%) already have had and would continue to have substantial surface disturbance due to Asarco’s mining operations.
(2) Production operations and support areas: 3,614 acres (33%) would be used to expand open pits, construct haul roads, and deposit solution-extraction rock. This would result in substantial disturbance to between 25% and 100% of the land surface.
(3) Transition: 875 acres (8%) would be used as “raveling areas” around overburden and leach rock deposition areas, access roads, storm water diversion ditches, and administrative facilities. This would result in some disturbance to between 5% and 25% of the land surface.
*1067(4) Intermittent use: 4,481 acres (41%) would not be subject to direct mining activity and would be used to consolidate Asarco’s ownership and to buffer neighboring landowners from mining operations.
(5) Long-range prospect: 1,733 acres (16%) could be used for mine development and support in the future resulting in an unknown degree of surface disturbance.
The selected lands are now encumbered by 751 mining claims or mill site claims under the Mining Law of 1872, of which 747 are held by Asarco. These claims are unpatented, and the BLM has not determined if they are valid. Every parcel of the selected lands except for Parcel CH-5 (comprising 480 acres) is encumbered by at least one such claim.
The offered lands comprise five parcels or groups of parcels: the Knisely Ranch Parcels (160 acres), the Gila River Parcel (320 acres), the Tomlin Parcels (320 acres), the McCracken Mountain Parcels (6,384 acres), and the Sacramento Valley Parcel (120 acres). Following the land exchange, no mining claims would exist or be permitted on the Knisely Ranch Parcels. The BLM would petition to withdraw the Gila River Parcel and Tomlin Parcels from mineral entry, which, if successful, would mean that only persons who had established a valid mining claim before withdrawal would be permitted to mine on those parcels. Clouser v. Espy, 42 F.3d 1522, 1524-25 (9th Cir.1994). The McCracken Mountain Parcels, which comprise 87% of the offered lands, and the Sacramento Valley Parcel would remain open to mineral entry. Of the 7,300 acres of offered lands, 1,126 acres exhibit moderate potential for locatable mineral resources, with the rest exhibiting low potential for locatable mineral resources.
The offered lands include riparian plant communities and important wildlife habitat, including habitat for some special status species, potential habitat for some threatened or endangered species, including peregrine falcons, and proposed critical habitat for the cactus ferruginous pygmy owl. The offered lands include segments of the Gila River Riparian Management Area, the Black Mountains (Burro) Herd Management Area, the Cerbat (Wild Horse) Herd Area, the Big Sandy (Burro) Herd Management Area, and the McCracken Desert Tortoise Habitat Area of Critical Environmental Concern.
Between 1995 and 1997, the BLM consulted with various federal, state, and local agencies, elected representatives, nongovernmental organizations, tribal governments, and private individuals concerning the land exchange. The BLM published a Draft Environmental Impact Statement (“DEIS”) in October 1998.
In January 1999, after having reviewed the DEIS, the federal Environmental Protection Agency (“EPA”) sent the BLM a three-page single-spaced letter accompanied by thirteen pages of single-spaced comments. The EPA’s letter stated, inter alia:
Over the past several decades, approximately one billion tons of material have been excavated at the Asarco Ray complex. The proposed action would enable Asarco to excavate and process approximately three billion more tons over the next 40 years. In several meetings, letters, and conference calls with BLM since scoping for this project began in 1994, EPA has recommended that the DEIS provide certain information that we believe would be useful and relevant in a NEPA analysis for a land exchange where the foreseeable future uses of mining are known. In our comment letter on the preliminary DEIS, we stated that the document did not appear to have evaluated all reasonable alternatives and strongly recommended that additional information regarding *1068the alternatives be included in the DEIS. In that letter and several others to the DEIS, we also recommended that the potential impacts of the land exchange and the foreseeable future mining be discussed in much greater detail in the DEIS and specifically outlined the needed information.
Although BLM has not received an acceptable mine plan of operations (MPO) from Asarco, it appears that Asarco has fairly specific plans for the selected parcels. We believe that additional detailed information regarding geology, geochemistry, hydrology, and biological resources is relevant and necessary for this analysis to constitute full disclosure under NEPA. It is also evident that all reasonable alternatives have not been evaluated and that impacts of foreseeable activities on the selected lands have not been sufficiently addressed in the DEIS. We are extremely dismayed that the BLM has ignored most of our recommendations in finalizing the DEIS and are particularly troubled that the DEIS was published at a time when our headquarters office was still discussing the issues with BLM headquarters and the two agencies had not yet come to a resolution.
We have rated this DEIS as EO-2— E nvir onmental Obj ections-Insufficient Information. We have strong objections to the proposed project because we believe there is potential for significant environmental degradation that could be corrected by project modification or other feasible alternatives.... We continue to contend that a substantial amount of information should be added to the EIS for BLM to meet its public disclosure obligation.
(Emphasis added).
Public hearings were held on the DEIS. The BLM received sixty-one comment letters or notifications of no comment from interested individuals and groups. After reviewing and responding to these comments, the BLM issued its Final Environmental Impact Statement (“FEIS”) in June 1999. The FEIS differs from the DEIS in only minor respects.
The FEIS analyzed the environmental, cultural, and socio-economic impacts of the proposed land exchange; the “Buck-eye Alternative,” under which the selected lands would decrease to 10,176 acres and the offered lands to 6,659 acres; the “Copper Butte Alternative,” under which the selected lands would decrease to 9,161 acres and the offered lands to 5,601 acres; and the “No Action Alternative,” under which no lands would be exchanged. The FEIS identified but elected not to study in depth seven other alternatives.
The FEIS stated that the “foreseeable uses of the selected lands are mining-related uses and are expected to occur under all alternatives.” (Emphasis added). As explained in the FEIS:
[A] land exchange is not required for mining-related activities to take place on the selected lands. Asarco currently holds the vast majority of the mining claims on the public lands selected for exchange, and through these mining claims, Asarco has the right to pursue development on the selected lands for mining or mining-related uses....
That is, as stated in the FEIS “foreseeable uses of the selected lands are assumed to be the same for all alternatives.” (Emphasis added).
The BLM’s stated assumption that mining was the foreseeable use for the selected lands and that the manner and intensity of mining would be “the same for all alternatives” — that is, whether or not there was a land exchange — played a critical role in the FEIS. The FEIS contains an analysis of the environmental consequences of mining for upland plant communities, riparian *1069plant communities, state and BLM special status plants, wildlife habitats, wildlife (including state and BLM special status wildlife as well as wildlife deemed threatened and endangered under federal law), and other resources. However, the FEIS contained only a single analysis, because the BLM assumed that the environmental consequences of mining would be the same under every alternative. Because the BLM assumed that the environmental consequences would be the same under every alternative, the FEIS contains no comparative analysis of those alternatives.
In April 2000, the BLM issued a Record of Decision (“ROD”) in which it did two things. First, the BLM amended two existing Resource Management Plans (“RMPs”) to change the designation of the selected lands under FLPMA. It amended the 1988 “Phoenix RMP” to change the designation of 9,906 acres in the White Canyon Resource Conservation Area from “retention” to “disposal.” And it amended the 1993 “Safford District RMP” to change the designation of 433 acres in the Long-Term Management Area from “retention” to “disposal.” These changes in the Phoenix and Safford District RMPs were prerequisites to the conveyance of the selected lands from public ownership. As a consequence of these changes, the BLM would no longer be required to manage the selected lands as multiple-use lands under FLPMA.
Second, the BLM approved the proposed land exchange. Section 206 of FLPMA forbids land exchanges unless the “public interest will be well served.” 43 U.S.C. § 1716(a). This section directs the Secretary of Interior to “give full consideration” to better land management and “needs for lands for the economy, ... food, fiber, minerals, and fish and wildlife” when determining the public interest. Id. In part, the ROD justified the exchange by denying that any harm to the public would result from conveying the selected lands to private ownership. The ROD concluded that the public interest would not be harmed by the conveyance by assuming, as the FEIS had assumed, that mining would be conducted in the same manner whether or not the exchange occurred. The ROD stated that “the BLM considers the continuation of mining as the foreseeable use of most of the selected federal lands whether the exchange occurs or not.”
The EPA, the federal Bureau of Indian Affairs, and the Sierra Club objected to the ROD. The BLM summarized their objection as follows: “A Mine Plan of Operation is necessary to complete analysis of the land exchange impacts. BLM’s assumption is wrong that the foreseeable use reflects mining that would take place whether or not land exchange occurs.” (Emphasis added). The ROD did not answer the objection, but instead referred the reader to the FEIS. The ROD stated, “This issue has been addressed in the FEIS General Response section 7.4.5 and 7.4.6.” In those sections of the FEIS, the BLM responded to the first sentence of the objection, stating that MPOs are not required for mining that is anticipated after the selected lands become privately owned. However, the BLM did not respond to the second sentence (italicized above), which objected that the BLM’s “assumption” that the same mining would occur was “wrong.”
In July 2001, Appellants filed an administrative appeal and a request to stay the land exchange with the Interior Board of Land Appeals (“IB LA”). When IB LA failed to act on the Appellants’ request within forty-five days as mandated by 43 C.F.R. § 4.21(b)(4), Appellants filed suit in federal district court. IBLA then stayed the land exchange pending its disposition of the appeal, and the district court sus*1070pended its proceedings pending a decision from IBLA.
In August 2004, IBLA denied the Appellants’ appeal. Ctr. for Biological Diversity, et al., 162 IBLA 268 (2004). One Administrative Judge wrote separately, concurring only in the result. For her, the difficult issue was whether the BLM had complied with NEPA. She wrote:
I am perturbed by BLM’s assertion that foreseeable consequences of this exchange are not possible to predict or are speculative. It appears that the record contains considerable information indicating where within the selected lands mineral resources are located and where they are not. It is this information that forms the basis for the classification of foreseeable uses (“existing,” “production,” “transition,” “intermittent use,” and “long-range prospect”) identified for the selected lands in the FEIS. Further, BLM changed its land use designations for the vast majority of the selected lands in the Phoenix and Safford Resource Management Plans from “resource conservation area” and “long term management area” to “suitable for disposal” in the context of implementing this exchange decision.... Combining these two points of information — the Icnowable classifications within the context of mining of the selected lands with the change in land designation — made foreseeable impacts more easily presentable in a manner not easily found in this EIS and less speculative than BLM suggests.
Id. at 291 (Hemmer, Admin.J., concurring) (emphasis added) (internal citations omitted).
On June 6, 2007, the district court granted summary judgment, rejecting Appellants’ challenge to the proposed land exchange. Appellants timely appealed to this court.
II. Standard of Review
This court reviews the district court’s grant of. summary judgment de novo. See, e.g., United States v. Tacoma, 332 F.3d 574, 578 (9th Cir.2003). The Administrative Procedure Act authorizes this court to set aside agency actions, findings, or conclusions that are “unsupported by substantial evidence” in the record. 5 U.S.C. § 706(2)(E). Under NEPA, “we must ensure that the agency has taken a ‘hard look’ at the environmental consequences of its proposed action.... [W]e must defer to an agency’s decision that is ‘fully informed and well-considered.’ However, we need not forgive a ‘clear error of judgment.’ ” Blue Mountains Biodiversity Project v. Blackwood, 161 F.3d 1208, 1211 (9th Cir.1998) (internal citations omitted). We review the BLM’s interpretation of FLPMA under the deferential “arbitrary and capricious” standard. See Webb v. Lujan, 960 F.2d 89, 91 (9th Cir. 1992).
III. Discussion
For the reasons that follow, we hold that substantial evidence in the record does not support the BLM’s assumption that mining would occur on the selected lands in the same manner regardless of the land exchange. Therefore, we hold that the BLM violated NEPA by failing to take a “hard look” at the environmental consequences of the exchange in the FEIS. We hold further that the conclusion in the ROD that the proposed land exchange is in the “public interest” within the meaning of FLPMA was arbitrary and capricious because it was based on an erroneous assumption. We do not reach the question whether the Mining Law of 1872 would be violated if the land exchange were to be completed in its current form. We discuss NEPA, FLPMA, and the Mining Law in turn.
*1071A. NEPA
In NEPA, Congress recognized the “profound impact” of human activities, including “resource exploitation,” on the environment and declared a national policy “to create and maintain conditions under which man and nature can exist in productive harmony.” 42 U.S.C. § 4331(a). To further this policy, NEPA “establishes ‘action-forcing’ procedures that require agencies to take a ‘hard look’ at environmental consequences.” Metcalf v. Daley, 214 F.3d 1135, 1141 (9th Cir.2000) (quoting Robertson v. Methoio Valley Citizens Council, 490 U.S. 332, 348, 109 S.Ct. 1835, 104 L.Ed.2d 351 (1989)). Chief among these procedures is the preparation of an environmental impact statement (“EIS”).
NEPA requires preparation of an EIS for “major Federal actions significantly affecting the quality of the human environment.” 42 U.S.C. § 4332(2)(C). Every EIS must “provide [a] full and fair discussion of significant environmental impacts” of the proposed agency action. 40 C.F.R. § 1502.1. An EIS selves two purposes:
First, [i]t ensures that the agency, in reaching its decision, will have available, and will carefully consider, detailed information concerning significant environmental impacts. Second, it guarantees that the relevant information will be made available to the larger audience that may also play a role in both the decisionmaking process and the implementation of that decision.
Dep’t of Transp. v. Pub. Citizen, 541 U.S. 752, 768, 124 S.Ct. 2204, 159 L.Ed.2d 60 (2004) (internal quotation marks and citations omitted).
In addition to the proposed agency action, every EIS must “[rjigorously explore and objectively evaluate all reasonable alternatives” to that action. 40 C.F.R. § 1502.14(a). The analysis of alternatives to the proposed action is “ ‘the heart of the environmental impact statement.’ ” Or. Natural Desert Ass’n v. Bureau of Land Mgmt., 531 F.3d 1114, 1121 (9th Cir.2008) (quoting 40 C.F.R. § 1502.14). “The existence of reasonable but unexamined alternatives renders an EIS inadequate.” Friends of Southeast’s Future v. Morrison, 153 F.3d 1059, 1065 (9th Cir.1998).
The FEIS prepared by the BLM examined the environmental impacts of the proposed land exchange and three alternatives: the Buckeye Alternative, the Copper Butte Alternative, and the No Action Alternative. Under the No Action Alternative, the exchange would not proceed, and the selected lands would remain under public ownership. A no action alternative in an EIS allows policymakers and the public to compare the environmental consequences of the status quo to the consequences of the proposed action. The no action alternative is meant to “provide a baseline against which the action alternative[ ]” — in this case, the land exchange — ■ is evaluated. Id. A no action alternative must be considered in every EIS. See 40 C.F.R. § 1502.14(d).
For the reasons that follow, we conclude that the FEIS improperly assumed that the environmental consequences of the land exchange alternative and the No Action Alternative would be the same, and that this assumption fatally undermined the analysis in the FEIS.
Under the Mining Law of 1872, Asarco has a right to engage in mining on the selected lands even if the exchange does not proceed. Asarco has this right based on its 747 unpatented mining and mill site claims. See, e.g., 30 U.S.C. § 612(a) (holders of unpatented mining claims can engage in “prospecting, mining or processing operations and uses reasonably incident thereto”); 43 C.F.R. §§ 3809.5, 3809.10(a) (claimants can engage in “casual use” mining on unpatented claims without even no*1072tifying the BLM); United States v. Shumway, 199 F.3d 1093, 1105 (9th Cir.1999) (“The owner of a mining or mill site claim does not need a patent, or a vested right to issuance of a patent, to possess and use the property.”); Independence Mining Co. v. Babbitt, 105 F.3d 502, 506 (9th Cir.1997) (an unpatented claim “entitles the claimant to ‘the right to extract all minerals from the claim without paying royalties to the United States’ ”) (citation omitted).
The BLM based its assumption that mining would occur in the same manner with or without the land exchange on the fact that Asarco already holds mining claims on the selected lands. However, if the proposed land exchange does not occur, the selected lands would remain in public hands. In that event, Asarco’s ability to conduct mining operations on its claims would be subject to the Mining Law of 1872. In contrast, if the proposed land exchange occurs, Asarco would own the selected lands in fee simple. In that event, Asarco’s use of the land would not be subject to the requirements of the Mining Law. A description of the operation of the Mining Law shows that the BLM’s assumption that the environmental consequences of these two alternatives would be the same is unwarranted.
Without the land exchange, proceeding under the Mining Law, Asarco would have to submit one or more Mining Plan of Operations (“MPOs”) to the BLM before engaging in mining operations on its claims if those operations are greater than a “casual use” that would disturb more than five acres of land. See 43 G.F.R. §§ 3809.11, 3809.21. “Casual use means activities ordinarily resulting in no or negligible disturbance of the public lands or resources,” such as collection of mineral specimens using hand tools. Id. § 3809.5. It is clear from the FEIS that Asarco intends to engage in mining operations on the selected lands that would be greater than casual use, and that one or more MPOs would be required.
Each MPO would have to provide a significant amount of information on Asarco’s mining plans, including “maps ... showing the location of exploration activities, drill sites, mining activities, processing facilities, waste rock and tailing disposal areas, support facilities, structures, buildings, and access routes”; “[preliminary or conceptual designs, cross sections, and operating plans for mining areas, processing facilities, and waste rock and tailing disposal facilities”; “[wjater management plans”; “[r]ock characterization and handling plans”; “[q]uality assurance plans”; “[sjpill contingency plans”; “[p]lans for all access roads, water supply pipelines, and power or utility services”; reclamation plans that address “[d]rill-hole plugging,” “[rjegrading and reshaping,” “[m]ine reclamation,” “[rjiparian mitigation,” “[wjildlife habitat rehabilitation,” “[t]opsoil handling,” “[isolation and control of acid-forming, toxic, or deleterious materials,” “[rjemoval or stabilization of buildings, structures and support facilities,” and “[pjost-closure management”; a detailed monitoring plan to ensure compliance with environmental laws and regulations; a “[reclamation cost estimate”; and “[Operational and baseline environmental information,” such as information on “geology, paleontological resources, cave resources, hydrology, soils, vegetation, wildlife, air quality, cultural resources, and socioeconomic conditions in and around the project area,” as the BLM may request. See id. § 3809.401.
For every MPO Asarco submits, the BLM may, depending on the details of the MPO and the public land involved, need to gather additional information before deciding whether to approve it. For example, the BLM may require Asarco to “collect adequate baseline data” against which to compare environmental data collected dur*1073ing or after mining takes place. Id. § 3809.411(a)(3)(i). The selected lands include dozens of archaeological sites, many of which, according to the FEIS, would be destroyed or severely disturbed if the land exchange proceeded. Consequently, the BLM may have to complete consultation required under the National Historical Preservation Act. See id. § 3809.411(a)(3)(iii). The BLM may have to complete consultation under the Endangered Species Act and/or the MagnusonStevens Fishery Conservation and Management Act. See id. The BLM may have to consult with Native American tribes. See id. § 3809.411(a)(3)(iv). It may have to consult with the State of Arizona to ensure that Asarco — which in the past has violated the federal Clean Water Act at the Ray Mine Complex-complies with State water quality requirements. See id. § 3809.411(a)(3)(ix). Further, an MPO must satisfy the performance standards described in 43 C.F.R. § 3809.420. These include standards regarding technology and practices, sequencing of operations, land use, mitigation, concurrent reclamation, availability of access routes, disposal of waste, protection of cultural and paleontological resources, fire prevention, and public safety. See 43 C.F.R. § 3809.420.
In connection with any approval of an MPO submitted by Asarco, the BLM would also have to comply with NEPA. See id. § 3809.411(a)(3)(h). NEPA requires the BLM to prepare an EIS before approving an MPO if that approval would constitute a “major Federal action[] significantly affecting the quality of the human environment.” 42 U.S.C. § 4332(2)(C). Based on the uses that Asareo and the BLM foresee for the selected lands, as detailed in the FEIS, it is certain that BLM approval of an MPO for the selected lands would constitute a “major federal action.” Each EIS would have to provide detailed information on the environmental impacts of Asarco’s planned mining as outlined in the MPO. Because the MPO submitted by Asarco would form the basis for any environmental review, an EIS prepared in connection with an MPO would provide a much more detailed analysis of the environmental consequences of the proposed mining and all reasonable alternatives than the FEIS that is now before us. This is not an empty requirement. Although “NEPA itself does not mandate particular results, but simply prescribes the necessary process” of preparing an EIS, that process is “almost certain to affect the agency’s substantive decision.” Robertson, 490 U.S. at 350, 109 S.Ct. 1835.
In addition, an MPO cannot be approved unless it complies with FLPMA. Under FLPMA, the Secretary of Interior is required to “take any action necessary to prevent unnecessary or undue degradation of the [public] lands.” 43 U.S.C. § 1732(b). BLM regulations define “unnecessary or undue degradation” to mean “conditions, activities, or practices” that fail to comply with the “performance standards in § 3809.420,” fail to comply with “other Federal and state laws related to environmental protection and protection of cultural resources,” are “not ‘reasonably incident’ to prospecting, mining, or processing operations” as defined in 43 C.F.R. § 3715.0-5, or “[f]ail to attain a stated level of protection or reclamation required by specific laws” in special status areas. 43 C.F.R. § 3809.5.
To summarize, if the selected lands remain in public hands, Asarco will be required to obtain the approval of the BLM for one or more MPOs before it can conduct additional mining operations on those lands. It is highly likely that the process of obtaining BLM approval of one or more MPOs will substantially affect the manner in which mining operations will occur on the selected lands. By contrast, if the *1074selected lands are conveyed to Asarco in fee simple, Asarco will be able to conduct its mining operations without being constrained in any way by the MPO process.
In its 1999 letter to the BLM, the EPA objected strenuously to the draft EIS. The EPA noted that “it appears that Asarco has fairly specific plans for the selected parcels,” and the EPA “continue[d] to contend that a substantial amount of information should be added to the EIS for the BLM to meet its public disclosure obligation.” In her 2004 separate concurrence in the IBLA’s decision, Administrative Judge Hammer noted that she was “perturbed by BLM’s assertion that foreseeable consequences of this exchange are not possible to predict or are speculative.” She wrote that the information available to the BLM “made foreseeable impacts more easily presentable in a manner not easily found in this EIS and less speculative than BLM suggests.” The FEIS itself contains detailed information about the mining activities that Asarco intends to conduct on the selected lands, as well as the acreage to be devoted to such activities.
It is thus plain from the record that both Asarco and the BLM have a fairly detailed knowledge of what Asarco intends to do if the land exchange is approved. This knowledge would permit the BLM to prepare a FEIS analyzing the likely contents of the one or more MPOs that Asarco would be required to submit in order to carry out its intentions on the selected lands if they were to remain in public hands, as well as the likely response by the BLM to such MPOs.
It is black letter law that NEPA requires a comparative analysis of the environmental consequences of the alternatives before the agency. In the case before us, that analysis would compare the environmental consequences of the no-aetion alternative, in which Asarco would own mining claims on government-owned land, and the land exchange alternative, in which Asarco would own the land in fee simple. Under the first alternative, Asarco would have to prepare MPOs in accordance with the Mining Law. Under the second alternative, Asarco would not be restricted in any way by the Mining Law of 1872. In these circumstances, NEPA requires a meaningful analysis of the different environmental consequences that would result from public ownership (with an MPO requirement) and private ownership (without an MPO requirement). Without such an analysis, the BLM has not conducted the “hard look” that NEPA requires. Rather, the BLM has averted its eyes from what is in plain view before it.
To summarize, NEPA requires a meaningful comparison of the alternative courses of action available to the BLM. To satisfy NEPA, the BLM must provide a meaningful analysis of the likely environmental consequences of the proposed exchange by comparing the likely environmental consequences of mining on the selected lands under a regime of approved MPOs with the likely environmental consequences of mining on the lands without the constraints imposed by the MPO process. The BLM has not done this. Indeed, it has not even attempted to do this. Rather, in describing the no action alternative in the FEIS, and in assuming that mining on the selected lands will take place in the same manner whether or not the exchange takes place, the BLM has improperly assumed, without analysis, that the MPO process would have no effect whatsoever on the manner and intensity of mining on the selected lands. In so doing, it has impermissibly “assumed the existence of the very plan being proposed.” Friends of Yosemite Valley v. Kempthorne, 520 F.3d 1024, 1026 (9th Cir. 2008).
*1075The BLM’s assumption that mining would take place in the same manner whether or not the exchange occurs is not supported by substantial evidence in the record. Indeed, it flies in the face of the evidence in the record. We therefore conclude that the BLM violated NEPA by failing to take a “hard look” at the environmental consequences of the land exchange.
B. FLPMA
In FLPMA, Congress declared that it is the policy of the United States to manage the public lands “in a manner that will protect the quality of scientific, scenic, historical, ecological, environmental, air and atmospheric, water resource, and archeological values.” 43 U.S.C. § 1701(a)(8). Congress also declared it a national policy to manage the public lands “in a manner which recognizes the Nation’s need for domestic sources of minerals, food, timber, and fiber from the public lands.” Id. § 1701(a)(12). The BLM and the Secretary of the Interior are responsible for administering FLPMA and satisfying this multiple use mandate.
FLPMA forbids land exchanges unless the “public interest will be well served by making that exchange.” Id. § 1716(a). FLPMA directs the Secretary of the Interior, in considering the public interest, to “give full consideration to better Federal land management and the needs of State and local people, including needs for lands for the economy, community expansion, recreation areas, food, fiber, minerals, and fish and wildlife.” Id. The Secretary must also “find[ ] that the values and the objectives which Federal lands or interests to be conveyed may serve if retained in Federal ownership are not more than the values of the non-Federal lands or interests and the public objectives they could serve if acquired.” Id.
In approving the land exchange, the ROD emphasized what the BLM saw as the advantages of acquiring the offered land. Those advantages include: (1) facilitating better federal land management by acquiring private lands within special areas of designation that exhibit a “checker board” land ownership pattern; (2) improving wildlife and Area of Critical Environmental Concern habitats by adding parcels to federal protection and management; (3) supporting resource objectives for improving riparian zones by acquiring parcels along the Big Sandy and Gila Rivers; (4) continuing to support mining activities by providing lands that will enable Asarco to plan expansions, comply with environmental permits, buffer operations from surrounding lands, and continue operating on parcels with approved mine plans of operations; and (5) improving management of mineral rights.
The ROD listed no disadvantages of conveying the selected lands into Asarco’s private ownership. The ROD stated, “An additional rationale for approving the land exchange is that the BLM considers the continuation of mining as the foreseeable use of most of the selected federal lands whether the exchange occurs or not.” In other words, the ROD, like the FEIS, assumed that mining would occur on the selected lands in the same manner whether or not the exchange took place. For the reasons discussed above, this assumption is unreasonable. The manner in which Asarco engages in mining on the selected lands may differ substantially depending on whether the land exchange occurs, and the environmental consequences will differ accordingly.
Because the ROD unreasonably assumed that mining would occur in the same manner, its analysis of the public interest under FLPMA is fatally flawed. Without an accurate picture of the environmental consequences of the land exchange, the BLM cannot determine if the “public interest will be well served by making the *1076exchange,” and the Secretary cannot determine if the “values and the objectives” which the selected lands “may serve if retained in Federal ownership are not more than the values” of the offered lands. We therefore hold that the conclusion in the ROD that the proposed land exchange is in the “public interest” within the meaning of FLPMA was arbitrary and capricious.
C. Resource Management Plans
In addition to approving the land exchange, the ROD approved changes to two Resource Management Plans (“RMPs”). First, it amended the Phoenix RMP by changing the designation of 9,906 acres of selected lands in the White Canyon Resource Conservation Area from “retention” to “disposal.” Second, it amended the Safford District RMP by changing the designation of 433 acres of selected lands in the Long-Term Management Area from “retention” to “disposal.” These changes were necessary in order to allow the conveyance of most of the selected lands into private hands.
Amending a resource management plan ordinarily constitutes “major federal action” requiring NEPA analysis. See Klamath Siskiyou Wildlands Ctr. v. Boody, 468 F.3d 549, 560-62 (9th Cir.2006). The BLM accordingly treated the plan amendments as major federal actions and analyzed them in the FEIS. As part of the no action alternative, the FEIS assumed that neither the land exchange nor the proposed amendments to the RMPs would take place.
For the same reasons that the analysis in the FEIS of the land exchange is inadequate under NEPA, so too is the analysis of the proposed RMP amendments. By assuming that mining would occur in the same manner on the selected lands regardless of whether the exchange occurred, the BLM assumed either that the RMPs would be amended even if the exchange did not occur, or that even if the RMPs were not amended the existing RMPs would not affect Asarco’s mining plans. There is nothing in the record supporting the first assumption that the RMPs would be amended absent the exchange, especially given that the BLM acknowledges that the amendments were prerequisites to the land exchange. And the second assumption — that the unamended RMPs would have no effect on mining — suffers from the same flaws discussed above. Just as the BLM must consider the constraints imposed by the MPO requirement for the no action alternative to the land exchange, so too must it consider the constraints the RMPs would impose if the amendments did not occur. We note that 94% of the selected lands are currently subject to RMPs.
The Appellants did not directly challenge the RMP amendments in their appeal to us. However, we note the incongruity of holding that the analysis in the FEIS of the no action alternative violates NEPA with respect to the land exchange but not with respect to the RMP amendments if the same erroneous assumption infects them both. We leave it to the district court to address this issue, as appropriate, on remand.
D. Mining Law of 1872
We do not reach the question whether the Mining Law of 1872 would be violated if the land exchange were to be effectuated on the current record. That is, we do not reach the question whether it would violate the Mining Law to effectuate a substantial land exchange that would permit a mining company entirely to avoid the restrictions that would result from the MPOs that would be required if the land were to remain in the public domain. That question may or may not be presented at a later time, if and when the BLM has complied with NEPA and FLPMA.
*1077Conclusion
We conclude that substantial evidence in the record does not support the BLM’s assumption that mining would occur in the same manner regardless of the land exchange. We therefore hold that in failing to provide a comparative analysis of the likely environmental consequences of the proposed land exchange, on the one hand, and the no action alternative, on the other, the BLM failed to take a “hard look” at the environmental consequences of the exchange in violation of NEPA. We hold further that the conclusion in the ROD that the proposed land exchange is in the “public interest” within the meaning of FLPMA was arbitrary and capricious because it was based on the BLM’s erroneous assumption. We do not reach the question whether the Mining Law of 1872 would be violated if the land exchange were to be effectuated on the current record.
We therefore REVERSE the decision of the district court approving the action of the BLM.