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Federal Register / Vol. 86, No. 185 / Tuesday, September 28, 2021 / Proposed Rules coarse resolution imparted by the vegetation mapping. Essentially, this process allows the model to be more accurate and applicable at a finer scale.
The critical habitat area was mapped using ArcMap version 10.6.1
Environmental Systems Research Institute, Inc. 2018, a Geographic Information Systems GIS computer application. We identified two critical habitat units in the White Mountains known to be occupied by Penasco least chipmunks as of 2019. We identified a third critical habitat unit between these two occupied units that has the physical and biological features required by the Penasco least chipmunk but has not yet been surveyed for occupancy.
We have determined that a designation limited to the two occupied units would be inadequate to ensure the conservation of the subspecies because there is only one remaining population, which has low resiliency and no redundancy, making it vulnerable to catastrophic or stochastic events and further compounding the risks of small population sizes. The risk of subspecies extinction from a disease outbreak, large wildfire, or extreme drought is high. A
low-resiliency single population provides no redundancy for the species, and a single catastrophic event could cause species extinction.
Areas Outside the Geographic Area Occupied at the Time of Listing Because we have determined known occupied areas alone are not adequate for the conservation of the species, we have evaluated whether any unoccupied areas are essential for the conservation of the species. We are proposing as critical habitat one unit situated between the two known occupied units that is currently considered unoccupied because of a lack of survey data. We have determined that it is essential for the conservation of the species as it provides important connectivity between the two occupied units and could support population expansion into this area, if not populated already.
Limited functional habitat exists within the White Mountains, and connectivity between known locations of Penasco least chipmunk is essential to the conservation of the subspecies because it provides more of the physical or biological features upon which the subspecies depends for feeding, sheltering and reproducing. This unit provides a link between the two known occupied units. The unit has all of the physical or biological features necessary for the conservation of the Penasco least chipmunk; its in the White Mountains, at elevations of 2,5003,597 meters 8,20011,800 feet, with rock outcrop,
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and the vegetation is characterized by meadow/grassland community within openings of spruce-fir forests.
Small, isolated populations of animals with restricted movement and low genetic diversity are more likely to become extirpated than larger populations with greater movement between sub-populations within them and greater genetic diversity. Due to the small population sizes found within the two occupied units, either or both could become extirpated from local catastrophic events or the deleterious effects of genetic bottlenecking resulting from inbreeding that reduces the viability of a population, if they had no connectivity. The unoccupied unit in between these two known occupied units has never been surveyed for Penasco least chipmunk, due to its remoteness and difficulty to access. It does, however, maintain all the physical or biological features of the occupied areas. We analyzed this using remote GIS vegetation and landscape feature data from the U.S. Forest Service and the U.S. Department of Agriculture National Agricultural Imagery Program.
It is possible the Penasco least chipmunk is present in the unoccupied unit; however, with no confirmed records, we are treating it as unoccupied for purposes of this designation.
Physical or biological features essential to the conservation of Penasco least chipmunk are areas within the White Mountains, between elevations of 2,5003,597 meters 8,20011,800 feet, that contain rock outcrops, and vegetation associated with meadow/
grassland communities within openings of spruce-fir forests. This unoccupied unit provides all of the physical or biological features to allow for breeding, feeding, sheltering and dispersal of Penasco least chipmunk. The unoccupied unit is within the White Mountains with varying elevations between 2,5003,597 meters 8,200
11,800 feet, and rock outcrops, and approximately 44 percent of this unit is classified as grass-forb mix or Gambel oak. We find that this unit currently contains the resources and conditions necessary to support multiple life processes i.e., breeding, feeding, sheltering and dispersal of the Penasco least chipmunk.
General Information on the Maps of the Proposed Critical Habitat Designation The proposed critical habitat designation is defined by the map or maps, as modified by any accompanying regulatory text, presented at the end of this document under Proposed Regulation Promulgation. We include more detailed information on the
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boundaries of the proposed critical habitat designation in the discussion of individual units, below. We will make the coordinates or plot points or both on which each map is based available to the public on https
www.regulations.gov under Docket No.
FWSR2ES20200042.
When determining proposed critical habitat boundaries, we made every effort to avoid including developed areas such as lands covered by pavement, buildings, and other structures because such lands lack physical or biological features necessary for the Penasco least chipmunk. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed lands. Any such lands inadvertently left inside critical habitat boundaries shown on the maps of this proposed rule have been excluded by text in the proposed rule and are not proposed for designation as critical habitat.
Therefore, if the critical habitat is finalized as proposed, a Federal action involving these lands would not trigger section 7 consultation under the Act with respect to critical habitat and the requirement of no adverse modification unless the specific action would affect the physical or biological features in the adjacent critical habitat.
We propose to designate as critical habitat lands that we have determined are occupied at the time of listing i.e., currently known to be occupied and that contain one or more of the physical or biological features essential to support life-history processes of the species. We have determined that the known occupied areas are inadequate to ensure the conservation of the species.
Therefore, we have also identified, and propose for designation as critical habitat, unoccupied areas that are essential for the conservation of the species. For those unoccupied areas, we have determined that it is reasonably certain that the unoccupied areas will contribute to the conservation of the species and contain one or more of the physical or biological features that are essential to the conservation of the species. We have also determined that the unoccupied areas fall within the regulatory definition of habitat at 50
CFR 424.02.
Proposed Critical Habitat Designation We are proposing to designate approximately 2,660 hectares 6,574
acres in three units in New Mexico as critical habitat for the Penasco least chipmunk. The critical habitat areas we describe below constitute our current best assessment of areas that meet the
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