The BLM currently authorizes 4,114 AUMs per year on 440,982 public acres, according to the Allotment Master Report at RAS.
The Buffalo Hills HMA coincides roughly with the Buffalo Hills pasture, as noted in Table 5 of the Final EA for resource enforcement actions in the Smoke Creek Complex.
The Western Watersheds map shows the arrangement. The EA was posted with other project documents in ePlanning.
The allotment is in the Improve category and the active AUMs have declined slightly from the amount authorized when the EA was published. Refer to Table 6.
Forage availability works out to a paltry 9.3 AUMs per year per thousand acres, enough to support 0.8 wild horses per thousand acres.
The HMA intersects 27.6% of the allotment according to Table 5, so the forage assigned to livestock inside the HMA should be around 1,135 AUMs per year, assuming the resource is evenly distributed across the parcel.
If it was shifted back to the horses, the AML could be increased by 94, for a total of 408.
Unfortunately, the current population exceeds that value.
Western Horse Watchers Association 
IMPORTANT INFO if you are interested in amending Resource Management Plans (RMPs) to include WILD EQUIDS AS NATIVE AMERICAN HISTORIC CULTURAL RESOURCE. THIS IS A MAJOR AND FATAL FLAW IN RMPs. https://www.endangeredspecieslawandpolicy.com/ceq-finalizes-first-phase-of-nepa-revisions.
Crafting a purpose and need statement. The 2020 Regulations clarified that an agency reviewing an application for a permit or other authorization must consider the purpose and need of the applicant when undertaking NEPA review (40 C.F.R. § 1502.13), and added conforming language to a new definition of “reasonable alternatives,” which indicated “reasonable alternatives” are those that are “technically and economically feasible, meet the purpose and need of the proposed action and, where applicable, meet the goals of the applicant” (40 C.F.R. § 1508.1(z)). The Phase I Regulations remove specific references to the purpose and need of an applicant in both 40 C.F.R. § 1502.13 and 40 C.F.R. § 1508.1(z), and revert both to NEPA regulatory language that was adopted by CEQ in 1978.
Agency NEPA procedures. The 2020 Regulations mandated that CEQ’s NEPA rules were the maximum requirements an agency could include in its agency-specific NEPA procedures (40 C.F.R. § 1507.3). The Phase I Regulations take the approach adopted in 1978, which indicate agency-specific NEPA procedures may go beyond those required under CEQ regulations.
Definition of “effects” or “impacts.” CEQ regulations adopted in 1978 defined “effects” of an action to include direct and indirect effects, and also required consideration of cumulative impacts. The 2020 Regulations removed the distinction between direct and indirect effects and required consideration only of those changes to the human environment that are reasonably foreseeable and have a reasonably close causal relationship to the proposed action or alternatives. The 2020 Regulations also removed references to cumulative impacts. Changes to the definition of “effects” and “cumulative impacts” were among the more controversial changes made by the 2020 Regulations. Pursuant to the Phase I Regulations, CEQ has reinstated the distinction between direct, indirect, and cumulative effects as they existed prior to the 2020 Regulations. However, in response to comments received during the public comment period, CEQ has clarified that “effects” and “impacts” include only those changes to the human environment from the proposed action or alternatives that are reasonably foreseeable.
Finally, the Phase I Regulations made final the previously issued interim final rule granting an extension for agencies to update their agency-specific NEPA implementation regulations. Pursuant to the Phase I Regulations, agencies have until September 14, 2023 to finalize agency-specific rules.