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Federal Register / Vol. 86, No. 161 / Tuesday, August 24, 2021 / Rules and Regulations
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Brooks 1997, pers. comm.; Service 2016, entire; Service 2017, entire; Trail 2017, pers. comm.. We have no new information that the timing, location, intensity, or duration of grazing has changed, with the exception of the Cascade-Siskiyou National Monument, where most grazing has been retired Colyer 2018, pers. comm.. The lack of specific information on the impacts of livestock grazing on the Franklins bumble bee limits our ability to connect the activity to any specific species response, and we do not anticipate grazing will increase in the future to a degree that may affect the viability of the species Bureau of Land Management 2016, pp. 96103.
Effects of Climate Change Specific impacts of climate change on pollinators are not well understood;
most of the existing information on climate change impacts to pollinators comes from studies on butterflies.
Studies specifically relating to bumble bees are scant, and we found no climate change information specific to the Franklins bumble bee. Changes in temperature and precipitation, and the increased frequency of storm events, can affect pollinator population sizes directly, by affecting survival and reproduction Intergovernmental Panel on Climate Change 2013, entire; Bale et al. 2002, p. 11; Roland and Matter 2016, p. 22. These climatic changes can also affect populations indirectly, by altering resource availability and species interactions Service 2018a, p. 36.
Bumble bee abundance for three species of Bombus in the Rocky Mountains increased when floral resources were available for more days, and the number of days when floral resources were available increased with greater summer precipitation and later snowmelt dates Ogilvie et al. 2017, p.
4. Several of the targeted Franklins bumble bee and western bumble bee survey reports between 2015 and 2017
include mention of widespread hot, dry climate affecting timing and abundance of floral resources during the surveys Bureau of Land Management 2015, p. 2;
Trail 2017, pers. comm.. Although the Olgilvie et al. study and the survey reports suggest potential indirect effects of climate change on Bombus, we have no information to indicate that the effects of climate change were connected to the decline of the Franklins bumble bee; numerous Bombus species persist in areas that are considered good quality habitat for the Franklins bumble bee Pool 2014, entire; Colyer 2016, entire. As a habitat generalist, Franklins bumble bee appears to forage on a variety of floral
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resources, and we have no information to suggest that they would not forage off of whatever floral resource was in bloom at the time they emerge from their nests. We have no information to suggest that any changes in the vegetation community to date led to the decline of the species.
In order to understand the potential future impact of climate change on Franklins bumble bee, we looked at climate change projection models.
Global climate projections are informative and, in some cases, the only or the best scientific information available for us to use. However, projected changes in climate and related impacts can vary substantially across and within different regions of the world Intergovernmental Panel on Climate Change 2007, pp. 812.
Therefore, we use downscaled projections when they are available and have been developed through appropriate scientific procedures because such projections provide higher-resolution information that is more relevant to spatial scales used for analyses of a given species see Glick et al. 2011, pp. 5861, for a discussion of downscaling.
Downscaled projections as of 2016
were available for our analysis of the Franklins bumble bee from the U.S.
Geological Surveys National Climate Change Viewer Alder, J. and S.
Hostetler. 2016, entire. The National Climate Change Viewer is based on the mean of 30 models, which can be used to predict changes in air temperature and precipitation for Jackson County, Oregon location of the last known occurrence record of Franklins bumble bee, for two greenhouse gas emission scenarios, RCP4.5 and RCP8.5. From the year 2020 to the year 2050, the model set shows an increase in the mean maximum air temperature of between 1.9 degrees Fahrenheit F 1 degree Celsius C RCP4.5 and 3.1 F 1.7 C
RCP8.5, and an increase in the mean annual minimum air temperature of between 1.0 F 0.3 C RCP4.5 and 2.7 F 1.5 C RCP8.5. For both scenarios, mean precipitation is predicted to decrease by approximately 0.4 inches 10 millimeters for both scenarios.
Projections for an increase in temperature and decrease in precipitation over the next 30 years may lead to alteration in the vegetation community in Franklins bumble bee habitat, including the varieties of floral resources that Franklins bumble bee relies on for nectar. However, we have no information to suggest that these changes will result in a decrease in the availability of nectar resources to the
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species. Some studies suggest that pollinators are responding to climate change with recent latitudinal and elevational range shifts such that there is spatial mismatch among plants and their pollinators; while this has been demonstrated in butterflies, it may be less of a factor for bumble bees Service 2018a, p. 36. As generalist foragers, bumble bees do not require synchrony with a particular plant species, although some bumble bee populations are active earlier in the season than in the past Bartomeus et al. 2011, p. 20646.
Projections for an increase in temperature and decrease in precipitation over the next 30 years may also affect the frequency or intensity of wildfires and storm events including flooding. These events could affect the availability of floral resources, the suitability of nest locations, and the survival of overwintering queens.
However, we do not have information projecting the timing, scope, or intensity of wildfires or storms; the stochastic nature of these events limits our ability to project the magnitude of impact on the future condition of Franklins bumble bee or its habitat, and hinders our ability to assess their impact on the viability of the species.
Summary Although habitat loss has had negative effects on bumble bees, we conclude it is unlikely to be a main driver of the decline of the Franklins bumble bee. Habitat appears generally intact and in good condition throughout the known, historical locations of the Franklins bumble bee and throughout all of the recent focused survey areas with the exceptions of the historical sites affected by the creation of Lake Applegate in the fall of 1980, and soil modification that occurred on a portion of the Gold Hill site in 2004. In our assessment, we found no information to suggest that destruction, degradation, or conversion of habitat occurred at a scope and magnitude that would cause it to be a primary factor in the decline of the Franklins bumble bee Service 2018a, pp. 3537. Furthermore, we have no information to suggest that habitat destruction or modification will increase in scope and magnitude to the point where it will be a primary stressor to the species in its range in the near future.
A number of diseases and parasites are known to occur in bumble bee populations. These include the protozoan parasite Crithidia bombi C.
bombi, the tracheal mite Locustacarus buchneri, the microsporidium parasitic fungus Nosema bombi N. bombi, as well as deformed wing virus. Pathogens
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