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Federal Register / Vol. 86, No. 43 / Monday, March 8, 2021 / Rules and Regulations right-of-way, or by conservation easements on private lands. In Washington, one of two sites that support Bradshaws lomatium is owned by the WDNR, and the State is actively working toward the conservation of the very large adjacent site that supports the majority of known individuals of the species. As the threat posed to Bradshaws lomatium from habitat loss is no longer considered significant, we additionally no longer consider State or Federal protections to be inadequate to address this threat.
The present threat to Bradshaws lomatium from modification of habitat due to invasion of prairies by nonnative, invasive plants and by woody species has been reduced in many populations due to active habitat management using herbicides, mowing, and prescribed fire, but ongoing habitat management is required to maintain these improvements. As noted above, across the range of Bradshaws lomatium, 75
percent of the known sites receive active management that benefits the species, and 58 percent of total sites have a management plan in place with goals for the conservation of Bradshaws lomatium, or for maintenance of the wet prairie habitat upon which it depends Service 2018, pp. 3639, Appendix A.
Based on the high proportion of sites protected or managed, the history of positive management observed to date, and ongoing efforts to further restore and protect wet prairie habitats, we have confidence that management of Bradshaws lomatium sites will continue to provide adequate protection to the species in the long term. This confidence is affirmed by the MOU
committing to long-term conservation of Bradshaws lomatium on Federal lands regardless of its listing status. We found no evidence that negative impacts due to parasitic organisms constitute a threat to the viability of Bradshaws lomatium.
Predation by voles appears to vary year to year, and can substantially reduce aboveground biomass and reproduction in years when vole abundance is high.
However, the effect on populations is estimated to be minimal over time as long as there is sufficient time for Bradshaws lomatium to regenerate taproot reserves between vole outbreaks Drew 2000, pp. 5455, and no consistent long-term declines attributable to vole predation have been reported Service 2018, p. 20.
Concerns over the possibility of inbreeding depression expressed at the time of listing are now reduced due to a subsequent study indicating that overall genetic diversity in Bradshaws lomatium is relatively high for a rare species Gitzendanner and Soltis 2001,
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pp. 352353, and is greater than that found in other rare Lomatium species Gitzendanner and Soltis 2000, p. 787, although the most disjunct population in southwestern Washington showed relatively lower genetic diversity than less geographically isolated populations Gitzendanner and Soltis 2001, p. 353.
The threat of inbreeding depression is further considered reduced since we now understand Bradshaws lomatium to be primarily an outcrossing species which promotes increased genetic diversity, rather than an obligate selfpollinating species as was believed at the time of listing Service 2018, pp. 7, 20.
The potential threat posed to Bradshaws lomatium from the effects of climate change is difficult to predict.
The primary threat to the species from the effects of climate change is likely reduced moisture availability due to warmer temperatures and alterations to precipitation patterns resulting in increased evapotranspiration Bachelet et al. 2011, p. 414; Steel et al. 2011, pp.
43; Kaye et al. 2013, p. 18. The vulnerability of Bradshaws lomatium to the effects of climate change, assessed over a range of potential future emissions scenarios, has been ranked as anywhere from low to moderate Steel et al. 2011, pp. 25, 89 to highly vulnerable Kaye et al. 2013, p. 20. Possible effects of climate change on Bradshaws lomatium include increased reproduction after increased early precipitation, temporal shifts in life cycle completion to earlier in spring earlier germination and seed set, increased mortality, and decreased recruitment USFWS 2018, p. 43. We assessed the potential impacts of climate change on Bradshaws lomatium projected out over a period up to 50
years in the future. Published assessments provide only qualitative appraisals of the potential response of Bradshaws lomatium to the effects of climate change; therefore, we characterized a worst case future scenario in terms we could use in our analysis of future condition. In consultation with species experts and conservation partners, we defined the worst case scenario as one where increased mortality and decreased recruitment culminate in a 50 percent reduction of all populations. We considered this to be a conservative approach, in that the actual effects on populations size are likely to be more moderate. Even in the face of such a severe population reduction, the species is anticipated to remain viable as indicated by appreciable levels of resiliency, redundancy, and
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representation. We estimated that populations currently in low condition or with very low abundance may be extirpated due to the combined effects of climate change impacts and stochastic events; this translated to an estimated loss of up to five small populations, with other populations reduced in size. However, even with a presumed 50 percent reduction in abundance, at least 14 to 16 populations of Bradshaws lomatium in moderate or high condition are expected to remain on the landscape with ongoing management. We do not anticipate any significant effect on representation, that is, the ability of the species to adapt to changing environmental conditions over time Service 2018, pp. 4246.
Cumulative Impacts When multiple stressors co-occur, one may exacerbate the effects of the other, leading to effects not accounted for when each stressor is analyzed individually. The full impact of these synergistic effects may be observed within a short period of time or may take many years before they are noticeable. For example, high levels of predation on Bradshaws lomatium during vole outbreaks can cause large temporary population declines but are not generally considered a significant threat to long-term viability;
populations that are relatively large and well-distributed should be able to withstand such naturally occurring events. However, the relative impact of predation by voles may be intensified when outbreaks occur in conjunction with other factors that may lessen the resiliency of Bradshaws lomatium populations, such as prolonged woody species encroachment; extensive nonnative, invasive plant infestations;
or possible hydrological alterations resulting from the effects of climate change.
Although the types, magnitude, or extent of potential cumulative impacts are difficult to predict, we are not aware of any combination of factors that is likely to co-occur with significant negative consequences for the species.
We anticipate that any negative consequence of co-occurring threats will be successfully addressed through the same active management actions that have contributed to the ongoing recovery of Bradshaws lomatium and that are expected to continue into the future. The best scientific and commercial data available indicate that Bradshaws lomatium is composed of multiple populations, primarily in moderate to high condition, which are sufficiently resilient, well distributed, protected, and managed such that they
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