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Federal Register / Vol. 86, No. 161 / Tuesday, August 24, 2021 / Rules and Regulations
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sustain populations in the wild over time. We use this information to inform our regulatory decision.
Summary of Biological Status and Threats In this discussion, we review the biological condition of the species and its resources, and the threats that influence the species current and future condition, in order to assess the species overall viability and the risks to that viability.
To assess resiliency and redundancy, we evaluated the change in Franklins bumble bee occurrences populations over time. To assess representation as an indicator of adaptive capacity of the Franklins bumble bee, we evaluated the spatial extent of occurrences over time.
We evaluated the change in resiliency, representation, and redundancy from the past until the present; however, due to the lack of observations of the species since 2006, we did not project anticipated future states of these conditions.
Our analyses indicate that the resiliency, redundancy, and representation of the Franklins bumble bee have all declined since the late 1990s. Historically, the species has always been rare and has one of the narrowest distributions of any Bombus species in the world. Even so, the abundance and distribution of Franklins bumble bee has declined significantly Service 2018a, pp. 1014;
the species has not been observed since 2006, despite intensive survey efforts in select portions of its historical range.
Search efforts for the species have been varied in timing, scope, intensity, and methodology. During the more intensive surveys from 1998 until the last observation in 2006, the Franklins bumble bee was observed at 14
locations, including 8 locations where it had not been previously documented. In 1998, 98 bees were found among 11
locations. Searchers found fewer and fewer bees after that year even though they continued extensive searches in multiple locations with the highest likelihood of finding the species.
Twenty bees were located in 1999, nine individuals were observed in 2000, and one individual was observed in 2001.
Although 20 Franklins bumble bees were observed in 2002, only 3 were observed in 2003 all at a single locality, and a single worker bee was observed in 2006. Despite continued intensive search efforts in these areas through 2019, there have been no confirmed observations of the Franklins bumble bee since 2006. Data allow us to estimate 43 potential populations of the species since 1921, when the first
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description of the species was published Service 2018a, pp. 11. From 1998 to 2006, we identified 14 potential populations. Since 2006, no populations have been located.
The vulnerability resulting from the Franklins bumble bees haplodiploid genetic system, as well as the loss in the abundance and spatial extent of its populations, suggest the resiliency, representation, and redundancy of the Franklins bumble bee have all declined significantly since the late 1990s. The losses in both the number of populations and their spatial extent render the Franklins bumble bee vulnerable to extinction even without further external stressors e.g., pathogens and insecticide exposure acting upon the species.
As part of our status assessment of the Franklins bumble bee, we looked at potential stressors affecting the species viability Service 2018a, pp. 2340.
Potential stressors that we analyzed for the Franklins bumble bee generally fit into three groups that correspond with Factors A habitat loss and fragmentation, C pathogens, or E
pesticide use, competition with nonnative bees, and effects of small population size. No potential stressors of the Franklins bumble bee correspond with Factor B. There has never been any indication that the Franklins bumble bee was at risk of overutilization for commercial, recreational, scientific, or educational purposes, and we did not find any new information to suggest this has changed. Existing regulatory mechanisms Factor D are discussed below in the context of how they help to reduce or ameliorate stressors to the Franklins bumble bee.
The 2010 petition identified destruction, degradation, and conversion of habitat as a threat to the Franklins bumble bee. In our 90-day finding on the 2010 petition 76 FR
56381; September 13, 2011, we noted that the petitioners provided substantial information on threats to the Franklins bumble bee from the destruction, modification, or curtailment of habitat, primarily due to the potential impacts of natural or prescribed fire. Because the loss and degradation of habitat has been shown to reduce both diversity and abundance in other Bombus species Potts et al. 2010, pp. 348349, we looked at the potential stressors of natural or prescribed fire, agricultural intensification, urban development, livestock grazing, and the effects of climate change Service 2018a, pp. 23
40.
Although conversion of natural habitat appears to be the primary cause of bumble bee habitat loss throughout
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the world Goulson et al. 2015, p. 2;
Kosior et al. 2010, p. 81, many researchers believe it is unlikely to be a main driver of the recent, widespread North American bee declines Szabo et al. 2012, p. 236; Colla and Packer 2008, p. 1388; Cameron et al. 2011, p. 665.
Despite uncertainties regarding the Franklins bumble bees habitat needs, we know they need 1 floral resources for nectaring throughout the colony cycle, and 2 relatively protected areas for breeding and shelter. Furthermore, the available information regarding locations where the species has been found indicates that the Franklins bumble bee is a generalist forager and that the species specific needs and preferences for these habitat elements are relatively flexible, plentiful, and widely distributed. While we can say that Bombus species in general might prefer protected meadows with an abundance of wildflowers, the Franklins bumble bee has been found in a wide array of sheltered and exposed habitat types at elevations ranging from 540 ft 162 m to 7,800 ft 2,340 m Thorp 2017, pers. comm..
Natural or Prescribed Fire Fire caused by both natural and human-caused factors has been an important change on the landscape in the range of the Franklins bumble bee.
Because fire reduces natural succession of forests through the burning of encroaching woody plants, fire is a primary factor in the maintenance of grassland and meadow habitat that can support Bombus species Shultz and Crone 1998, p. 244; Huntzinger 2003, p.
2. With the increase in human development came fire suppression to limit damage to manmade structures.
Fire suppression allows woody encroachment to occur, and the diverse landscape created by fire open areas mixed within forested areas is slowly being replaced by increasing areas of denser forested habitat; the open areas that facilitated the growth of diverse understory plant communities are being reduced from their historical condition Ruchty 2011, p. 26. Conifer species now cover some of the area that was previously open meadow habitat in the range of the Franklins bumble bee Panzer 2002, p. 1297; Shultz and Crone 1998, p. 244. Although this loss of habitat by fire suppression may have limited the availability and diversity of floral resources, as well as nest and overwintering habitat for the Franklins bumble bee, healthy meadow habitat remains in areas where the Franklins bumble bee was previously found Godwin 2017, pers comm.; Colyer 2017, pers. comm., and it is unlikely
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