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Federal Register / Vol. 86, No. 166 / Tuesday, August 31, 2021 / Rules and Regulations
however, we welcome any new information on the likelihood of mining impacts to inform subsequent Service actions.
20 Comment: A commenter notes that Bartrams stonecrop rock habitat should minimize wildfire, erosion, sedimentation, and burial, and that the 12-month finding for Hexalectris colemanii concluded that wildfire was not a risk, yet it occurs in the same habitat as Bartrams stonecrop.
Response: The crevices in the rock habitat where Bartrams stonecrop occurs provide shade, shelter, and soil moisture retention, and they provide the plant some protection from burning due to a lack of surrounding vegetation serving as fuel for fire in the rocky terrain. However, overstory tree and shrub species that provide shade to Bartrams stonecrop plants may be impacted by fire. Due to the location of plants in crevices or shallow soil pockets in steep canyons, adherence to substrate or soil is tenuous, and plants can be easily dislodged due to post-fire flooding, foot traffic, eroding soil, or falling rocks.
Unlike Bartrams stonecrop, Hexalectris colemanii Colemans coralroot is an almost exclusively subterranean species and is likely capable of resprouting following fire. In addition, the threats of nonnative plants e.g., Eragrostis lehmanniana Lehmanns lovegrass and Melinis repens rose natal were not considered to be threats to the Colemans coralroot 78 FR 76795; December 19, 2013, but are considered to be a threat to Bartrams stonecrop. These nonnative plants increase fire risk and alter the fire regime frequency and severity within Bartrams stonecrop habitat.
We are aware of 11 wildfires that occurred in known Bartrams stonecrop sites from 20072017, killing some Bartrams stonecrop individuals and removing shade in some sites. Wildfires have burned in all nine sky island mountain ranges of southern Arizona with known Bartrams stonecrop occurrences within the last decade.
Wildfire could potentially cause extirpation of small Bartrams stonecrop populations throughout the range of the species and have negative impacts on larger populations. Bartrams stonecrop seeds are very tiny, reside at or near the soil surface Shohet 1999, p. 48, and show no characteristics that would promote survival in a wildfire.
21 Comment: Three commenters stated that there is no evidence that erosion, sedimentation, or burial are significant threats to Bartrams stonecrop.

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Response: Erosion, sedimentation, and burial of Bartrams stonecrop individuals may occur as a result of mining, livestock pressure, recreation trails and roads, flooding events, cross border human activity, and postwildfire runoff. Bartrams stonecrop is found in crevices or shallow soil pockets in steep canyons where adherence to substrate or soil is necessarily tenuous. Individual plants can be easily dislodged from these positions due to flooding, foot traffic, eroding soil, or falling rocks.
Individuals dislodged by erosion and covered by rock fall have been observed in the Rhyolite Canyon subpopulation Service 2020a, p. 76. Similarly, more than a half dozen individuals dislodged from trailside infrastructure were lost to erosion in the Madera population Shohet 1999, p. 60. The effects of erosion, sedimentation, and burial and the loss of Bartrams stonecrop individuals are exacerbated in small populations.
22 Comment: Some commenters stated that fire may not be so important for this species and that an altered fire regime poses an uncertain threat to Bartrams stonecrop.
Response: The Madrean evergreen woodlands of the sky islands where Bartrams stonecrop occurs have evolved with frequent low-severity fire with an interval of 10 to 30 years between relatively widespread fires in the pine-dominant forests Swetnam et al. 2010, p. 4. Due to a variety of human activities in the landscape e.g., excessive livestock grazing, fuelwood cutting, nonnative introduction and expansion, and fire suppression starting around the turn of the last century through the mid-1900s, these woodlands now have high fuel loads, and high-severity fires are becoming increasingly more common Swetnam et al. 2010, p. 11; FireScape 2016, entire.
There is no evidence that such large, stand-replacing fires occurred historically; for example, fire-scar studies have revealed that only lowintensity surface fire regimes occurred within the range of Bartrams stonecrop for the past three to five centuries Swetnam et al. 2010, p. 15.
Crevices provide shade, shelter, and soil moisture retention, and offer Bartrams stonecrop plants protection from burning due to a lack of surrounding vegetation for fuel in the rocky terrain. Regardless, Bartrams stonecrop individuals have been burned. We are aware of 11 wildfires that occurred in known Bartrams stonecrop sites from 20072017, killing some Bartrams stonecrop individuals and removing shade in some sites
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Ferguson 2014, pp. 910, 15, 2829;
Ferguson 2016a, p. 13; Ferguson 2016b, entire; Ferguson 2017c, p. 32; Ferguson 2017h, p. 2. Wildfires have burned in all nine sky island mountain ranges of southern Arizona with known Bartrams stonecrop occurrences within the last decade. Wildfire could potentially cause extirpation of small Bartrams stonecrop populations throughout the range of the species and have negative impacts on larger populations. Bartrams stonecrop seeds are very tiny, reside at or near the soil surface Shohet 1999, p. 48, and show no characteristics that would promote survival in a wildfire.
Indirect threats to the species from fire include increased runoff of floodwaters, post-fire flooding that may scour habitat, deposition of debris and sediment originating in the burned area that could cover individuals, erosion of habitat, changes in vegetation community composition and structure, increased presence of nonnative plants, alterations in the hydrologic and nutrient cycles, and loss of overstory canopy shade essential for maintaining Bartrams stonecrop microhabitat.
23 Comment: A commenter expressed that Bartrams stonecrop should be listed as endangered and critical habitat should be designated.
Response: When making a listing decision for a species under the Act, the Service must determine if the current status of the species indicates it is in danger of extinction throughout all or a significant portion of its range an endangered species or likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range a threatened species. In determining whether a species meets either definition, we must evaluate all identified threats by considering the expected response by the species, and the effects of the threatsin light of those actions and conditions that will ameliorate the threatson an individual, population, and species level. We evaluate each threat and its expected effects on the species, and then analyze the cumulative effect of all of the threats on the species as a whole.
We also consider the cumulative effect of the threats in light of those actions and conditions that will have positive effects on the speciessuch as any existing regulatory mechanisms or conservation efforts. The Secretary determines whether the species meets the Acts definition of an endangered species or a threatened species only after conducting this cumulative analysis and describing the expected effect on the species now and in the foreseeable future.

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