Areas of Critical Environmental Concern: what they are, where they are, and why they matter

An Area of Critical Environmental Concern, ACEC for short, is public land BLM has singled out as needing special care. The name is the government's own, written into the Federal Land Policy and Management Act of 1976, the law that tells the Bureau of Land Management how to run the public land it manages. The law defines the term in one sentence:

(a) The term "areas of critical environmental concern" means areas within the public lands where special management attention is required (when such areas are developed or used or where no development is required) to protect and prevent irreparable damage to important historic, cultural, or scenic values, fish and wildlife resources or other natural systems or processes, or to protect life and safety from natural hazards.43 U.S.C. 1702 (FLPMA section 103), United States Code, 2024 edition, GPO govinfo, read Oct 18, 2026

So an ACEC is public land where BLM has found something that needs special attention: a historic or cultural site, a view, fish or wildlife, a natural system or process, or a natural hazard to people. The same law tells BLM to give these places priority when it develops or revises a land use plan:

(3) give priority to the designation and protection of areas of critical environmental concern;43 U.S.C. 1712 (FLPMA section 202), United States Code, 2024 edition, GPO govinfo, read Oct 18, 2026

Relevance, importance, and special management

Before BLM can designate an area, three things have to hold: two tests written in its planning rules, and the law's own condition that "special management attention is required." The first test is relevance: is the value really there?

(1) Relevance. There shall be present a significant historic, cultural, or scenic value; a fish or wildlife resource or other natural system or process; or natural hazard.43 CFR 1610.7-2, eCFR, title 43 text of Oct 8, 2026, read Oct 18, 2026

The second is importance: does it have substantial significance, usually more than local?

(2) Importance. The above-described value, resource, system, process, or hazard shall have substantial significance and values. This generally requires qualities of more than local significance and special worth, consequence, meaning, distinctiveness, or cause for concern. A natural hazard can be important if it is a significant threat to human life or property.43 CFR 1610.7-2, eCFR, title 43 text of Oct 8, 2026, read Oct 18, 2026

The rule's text quoted here is the one in force today. BLM's 2024 Public Lands Rule, "Conservation and Landscape Health" (89 FR 40308), had rewritten it. A final rule published May 12, 2026, "Rescission of Conservation and Landscape Health Rule" (91 FR 25787), rescinded the 2024 rule and put this text back, effective June 11, 2026.

BLM's 1988 manual spelled out what counts. Relevance can be met by a cultural site, a wildlife habitat, a rare plant community, a rare geological feature, or a natural hazard. Importance can be met by qualities that are more than locally significant, or fragile, rare, irreplaceable, or vulnerable to change. A natural hazard can meet the relevance test too: the manual names avalanche, dangerous flooding, landslides, unstable soils, seismic activity and dangerous cliffs.

BLM Manual 1613 (1988), the two passages, word for word

The manual quoted here is BLM's 1988 release. BLM replaced it on August 7, 2024, and rescinded that replacement on May 29, 2026 with none in its place: "Both regulatory and policy procedures for ACECs are under review for revision." We found no BLM statement that the 1988 text governs again. We quote it for how BLM long read the rule's two tests.

A. Relevance. An area meets the "relevance" criterion if it contains one or more of the following: 1. A significant historic, cultural, or scenic value (including but not limited to rare or sensitive archeological resources and religious or cultural resources important to Native Americans). 2. A fish and wildlife resource (including but not limited to habitat for endangered, sensitive or threatened species, or habitat essential for maintaining species diversity). 3. A natural process or system (including but not limited to endangered, sensitive, or threatened plant species; rare, endemic, or relic plants or plant communities which are terrestrial, aquatic, or riparian; or rare geological features). 4. Natural hazards (including but not limited to areas of avalanche, dangerous flooding, landslides, unstable soils, seismic activity, or dangerous cliffs). A hazard caused by human action may meet the relevance criteria if it is determined through the resource management planning process that it has become part of a natural process.BLM Manual 1613, Areas of Critical Environmental Concern, Rel. 1-1541, 9/29/88, section .11 (PDF page 7), read Oct 18, 2026

B. Importance. The value, resource, system, process, or hazard described above must have substantial significance and values in order to satisfy the "importance" criteria. This generally means that the value, resource, system, process, or hazard is characterized by one or more of the following: 1. Has more than locally significant qualities which give it special worth, consequence, meaning, distinctiveness, or cause for concern, especially compared to any similar resource. 2. Has qualities or circumstances that make it fragile, sensitive, rare, irreplaceable, exemplary, unique, endangered, threatened, or vulnerable to adverse change. 3. Has been recognized as warranting protection in order to satisfy national priority concerns or to carry out the mandates of FLPMA. 4. Has qualities which warrant highlighting in order to satisfy public or management concerns about safety and public welfare. 5. Poses a significant threat to human life and safety or to property.BLM Manual 1613, Areas of Critical Environmental Concern, Rel. 1-1541, 9/29/88, section .11 (PDF page 7), read Oct 18, 2026

On BLM's map today, the values it found most often are a natural system in 731 areas, a wildlife resource in 537 and a cultural value in 419. BLM's map fills in no importance finding for 237 areas, every area in the Idaho and Montana/Dakotas offices among them. BLM's rules ask for the finding before any designation. Where the map leaves it blank, we haven't read the plan to say. More were designated in 2016 than in any other year: 230. The oldest on the list date from 1980, and the newest from 2025.

How the rules got here

Congress named ACECs in 1976, in FLPMA. BLM's rule for designating them, 43 CFR 1610.7-2, dates from May 5, 1983, and its manual from September 29, 1988. The 2024 Public Lands Rule, published May 9, 2024, rewrote them, and BLM issued a new manual on August 7, 2024. BLM rescinded that rule on May 12, 2026, putting the old ACEC rule back, effective June 11, 2026, and rescinded the 2024 manual on May 29, 2026 without issuing another. A new proposed rule, RIN 1004-AF53, cleared White House review on October 8, 2026. Read the full history of the ACEC rules.

1,120 areas covering 25.0 million acres, all in the West, managed by 11 of BLM's state offices: Alaska and ten in the lower 48. An office's ground can cross a state line. The Oregon/Washington office manages BLM's ground in Washington, where 15 of the areas are, in the Spokane District plans. Counted from BLM's lines, these lie wholly outside their office's state: 15 of the Oregon/Washington office's in Washington, 5 of the California office's in Nevada, 2 of the Montana/Dakotas office's in South Dakota and 1 of the Arizona office's in California. This site shows designated areas only. Nominations under consideration in open plans aren't on it.

California has the most lines, 238, and the most acres, 7.9 million. Alaska is next by acres, 7.5 million, in 40 areas. A line can be a few acres or most of a county: the largest is Western Arctic Caribou Insect Relief ACEC in Alaska, and the smallest, Heritage Sites in Utah, is under three acres. The whole list, by BLM state office:

Each line marks something BLM found worth special care. On BLM's map, 731 areas hold a natural system, 537 hold a wildlife resource and 419 hold a cultural value. And the lines aren't empty: our count places at least 11,178 active mining claims inside 163 of them. Every line comes from a land use plan in which BLM designated that ground for special management.

Designation doesn't by itself close the land or turn it into a park. It happens inside a land use plan, and the plan says what the care will be: BLM's rules call it special management attention, and the plan can limit what's permitted inside the line. BLM's map has two yes-or-no fields about each area's special management, "protect" and "prevent". BLM defines both as guarding against irreparable damage to the area's values, and what the management actually is lives in the plan. Of the 755 areas in the six state offices that fill the fields (Alaska, Arizona, California, New Mexico, Oregon/Washington and Utah), 515 are marked "protect" and 563 "prevent." Colorado, Idaho, Montana/Dakotas, Nevada and Wyoming leave both at "no" for every area.

The public gets a say before a line is final. When BLM approves a draft plan that proposes ACECs, its rules require a notice in the Federal Register listing each proposed area and any limits on use that would come with it, with 60 days to comment:

(b) The State Director, upon approval of a draft resource management plan, plan revision, or plan amendment involving ACECs, shall publish a notice in the Federal Register listing each ACEC proposed and specifying the resource use limitations, if any, which would occur if it were formally designated. The notice shall provide a 60-day period for public comment on the proposed ACEC designation. The approval of a resource management plan, plan revision, or plan amendment constitutes formal designation of any ACEC involved. The approved plan shall include the general management practices and uses, including mitigating measures, identified to protect designated ACEC.43 CFR 1610.7-2, eCFR, title 43 text of Oct 8, 2026, read Oct 18, 2026

That 60-day window came back on June 11, 2026, when BLM's rescission of the 2024 Public Lands Rule took effect, and it's one of the things commenters asked BLM not to bring back. They called these comment periods "a hindrance to streamlining the designation and de-designation process."

A designation can also come off. BLM has a second list of areas that used to be designated or were replaced, and none of them is counted here. The Carrizo Plain in California is one: BLM's list of past areas carries a Carrizo Plain ACEC of 253,389 acres designated in 2010, and no designated ACEC lies inside the monument today.

Designation doesn't empty the land. Our records hold the public authorizations on federal land: mining claims, oil and gas leases, geothermal leases, rights of way and grazing allotments, each from the agency system that issues it. For each of the 1,120 areas we counted the claims, leases and rights of way whose mapped point falls inside BLM's own boundary, tested against the real shape, and the grazing allotments whose boundary touches it. A claim's point comes from the land description BLM records for it, often to the quarter section, not from the stakes on the ground.

On Oct 20, 2026 that found at least 11,740 active mining claims and leases inside 237 areas, and at least 6,353 more claims filed and pending. Claim counts are a floor: 58,102 of BLM's 563,300 open claims couldn't be placed on the ground. There are 4,646 rights of way inside 533 areas, counted apart, because a right of way is a grant for something built, not a claim or a lease. A grazing allotment covers part of 789 areas. The other 175 have nothing placed inside.

Mining claims are most of the extraction: at least 11,178 active in 163 areas, and four areas in the California desert hold 3,631 of them: Fremont-Kramer (1,487), Pinto Mountains (983), Ivanpah (703) and Picacho (458).

Who holds them

BLM's map of claims and leases says where each one is and what kind it is, but not who holds it. BLM records the holder in a different system, its case records at mlrs.blm.gov, one case at a time. So for every authorization inside a line we read that page and take the holder as BLM lists it, with the page and the day. BLM withholds some private individuals' names under the Privacy Act, and we show those as withheld by BLM. Its records name other private individuals, and we don't print those names either: where BLM's record names a person rather than a business or an agency, we show "A private individual, name withheld by this site" instead. By Oct 20, 2026, 8:18am PT, BLM named a holder for 20,270 of the 22,739 claims, leases and rights of way inside the lines and withheld 1,832 names. Of the names it gives, we don't print 103, because they're private individuals'. Inside Fremont-Kramer, the California desert line with the most active claims, the holder with the most is RED RIVER CREEK MINING GROUP LLC, with 818 of its 1,487 active claims.

The rule is RIN 1004-AF53, "Planning and Designation of Areas of Critical Environmental Concern." It first appeared on the government's rulemaking agenda, the Unified Agenda, on July 3, 2026. The Bureau sent it to the White House review office, OIRA, on July 13, 2026. OIRA finished on October 8, 2026, 87 days later, "Consistent with Change," which means the draft was changed during the review. It's a proposed rule, and it wasn't in the Federal Register at our last check, Oct 18, 2026, 12:36pm PT, so its text isn't public yet.

1. Jul 13, 2026Sent to the White House for review
2. Oct 8, 2026The White House finished its review: "Consistent with Change"
3. not yetPublished in the Federal Register
   Not in the Federal Register at our last check, Oct 18, 2026, 12:36pm PT.
4. not yetComment window closes
   The Register sets the deadline the day it publishes. We read it from there.

What the record says so far

Its text isn't public, so the record says little about it yet. It's a proposed rule that would change how BLM drafts every land use plan, and how it designates ACECs. Its label, under Executive Order 14192, is Deregulatory, and the White House review office sent it back "Consistent with Change" after seven meetings with outside groups, plus one group OIRA lists as a no-show. Its abstract, word for word:

The purpose of this rulemaking is to establish in regulations an updated process for the approval of the development, revision, amendment, and maintenance of land use plans, as provided for by the Federal Land Policy and Management Act of 1976, for public lands administered by the Bureau of Land Management (BLM). Additionally, this rulemaking will provide clarification of the process the BLM uses for designating Areas of Critical Environmental Concern.Unified Agenda entry for RIN 1004-AF53, Publication ID 2026, reginfo.gov (OMB OIRA), read Oct 18, 2026

And the label the government gave it under Executive Order 14192:

EO 14192 Designation: DeregulatoryUnified Agenda entry for RIN 1004-AF53, Publication ID 2026, reginfo.gov (OMB OIRA), read Oct 18, 2026

Who met with the White House about it

While OIRA held the rule, 8 outside groups asked for meetings, which OIRA logs: seven meetings, plus one group OIRA lists as a no-show. Read about the rule and its meetings.

Everything here comes from a public record we can point to.

The areas are BLM's own, from its map of designated ACECs. We read BLM's list and save every read. The last one finished Oct 20, 2026, 8:25am PT and found 1,120 areas. What's inside is our own count, made Oct 20, 2026, 8:30am PT. Who holds a claim is read from BLM's case records, one serial at a time. The rule is read from reginfo.gov, and the law from govinfo.gov, eCFR and BLM's own manual, each quote copied word for word, with its address.

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