Biological Evaluation for Western Bumble Bee Bombus Occidentalis (Greene, 1858)

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Biological Evaluation for Western Bumble Bee Bombus occidentalis (Greene, 1858)

Photo of Bombus occidentalis about to land on Camas Camassia quamash, July 30, 2013 at Butterfly Valley Botanical Area, Plumas National Forest Service by Gary Zamzow, used by permission.

Written by: J. Furnish, May 2012; Updated September, 2013 Reviewed by: Stephanie Coppeto, Wildlife Biologist, LTBMU, April 2013 Adapted for: Lassen 15 Restoration Project by John Clark, Wildlife Biologist Modoc National Forest, November 2015, Revised October 2016

Distribution of the western bumble bee Bombus occidentalis in the PSW Region and North America Bombus occidentalis currently occurs on many national forests throughout California (Figure 1) and in all states adjacent to California (Figure 2). Historically, the species was broadly distributed across western North America along the Pacific Coast and westward from Alaska to the Colorado Rocky Mountains (Thorp and Shepard 2005, Koch et al. 2012). Historically, B. occidentalis was one of the most broadly distributed bumble bee species in North America (Cameron et al. 2011). Currently, the western bumble bee is experiencing severe declines in distribution and abundance due to a variety of factors including diseases and loss of genetic diversity (Tommasi et al. 2004, Cameron et al. 2011, Koch et al. 2012).

Figure 1. Map of PSW national forests with historic (prior to 2000) vs. recent (post) collections of the western bumble bee Bombus occidentalis.

There are 116 collection records for the western bumble bee Bombus occidentalis on nine national forests of the PSW Region (Hatfield 2012): Eldorado (2), Klamath (15), Lake Tahoe Basin Management Unit (7), Lassen (29), Modoc (3), Plumas (22), Shasta-Trinity (25), Six Rivers (5) and Tahoe (6). There are only 25 collection records from national forest lands since 2000: 21 are on the Lassen, three are on the Plumas, and one is on the Lake Tahoe Basin

Management Unit (Figure 1).

Figure 2. Distribution of the western bumble bee Bombus occidentalis in the United States. At left, individual collection sites are shown as yellow dots and green indicates the known range (reproduced from Koch et al. 2012). At right, collection sites for Bombus occidentalis and other bumble bee species. The orange portion of the circle indicates the proportion of the collection comprised of B. occidentalis. The figure was modified from Cameron et al. (2011).

Bumble bees introduced from Europe for commercial pollination apparently carried a microsporidian parasite, Nosema bombi, which has been introduced into native bumble bee populations. Highest incidences of declining B. occidentalis populations are associated with highest infection rates with the Nosema parasite, and the incidence of Nosema infection is significantly higher in the vicinity of greenhouses that use imported bumble bees for pollination of commercial crops (Cameron et al. 2011).

Although the general distribution trend is steeply downward, especially in the west coast states, some isolated populations in Oregon and the Rocky Mountains appear stable (Rao et al. 2011, Koch et al. 2012). The overall status of populations in the west is largely dependent on geographic region: populations west of the Cascade and Sierra Nevada mountains are experiencing dire circumstances with steeply declining numbers, while those to the east of this dividing line are more secure with relatively unchanged population sizes. The reasons for these differences are not known.

Habitat & Life History Management Considerations Within Suitable Habitat Areas

Bumble bees are threatened by many kinds of habitat alterations that may fragment or reduce the availability of flowers that produce the nectar and pollen they require, and decrease the number of abandoned rodent burrows that provide nest and hibernation sites for queens. An example of a habitat where Bombus occidentalis was recently observed in July 2013 is the Darlingtonia Bog at Butterfly Valley Botanical Area on the Plumas National Forest (see Figure 3).

Major threats that alter landscapes and habitat required by bumble bees include agricultural and urban development. Exposure to organophosphate, carbamate, pyrethroid and particularly neonicotinoid insecticides has recently been identified as a major contributor to the decline of many pollinating bees, including honey bees and bumble bees (Henry et al. 2012, Hopwood et al. 2012, Krupke et al. 2012). In the absence of fire, native conifers encroach upon meadows, which also decreases foraging and nesting habitat available for bumble bees. 3

Figure 3. Photos of Darlingtonia bog habitat at Butterfly Valley Botanical Area, Plumas National Forest, where Bombus occidentalis was observed in July 2013.

According to studies done in England (Goulson et al. 2008), grazing during the autumn and winter months may provide excellent bumble bee habitat and prevent the accumulation of coarse grasses. Heavy grazing and high forage utilization should be avoided since flowering plants providing necessary nectar and pollen may become unavailable, particularly during the spring and summer when queens, workers and males are all present and active.

The following account of bumble bee life history is summarized from Heinrich (1979) and illustrated in Figure 4: Queens overwinter in the ground in abandoned rodent (i.e. mouse, chipmunk or vole) nests at depths from 6-18 inches and typically emerge about mid-March. The queen then lays fertilized eggs and nurtures a new generation. She first creates a thimble-sized and shaped wax honey pot, which she provisions with nectar-moistened pollen for 8-10 individual first-generation workers when they hatch. The larvae will receive all of the proteins, fats, vitamins and minerals necessary for growth and normal development from pollen. Eventually all the larvae will spin a silk cocoon and pupate in the honey pot. The workers that emerge will begin foraging and provisioning new honey pots as they are created to accommodate additional recruits to the colony. Individuals emerging from fertilized eggs will become workers that reach peak abundance during July and August. Foraging individuals are largely absent by the end of September. Those that emerge from unfertilized eggs become males, which do not forage and only serve the function of reproducing with newly emerged queens. During the season, a range of 50 to hundreds of individuals may be produced depending on the quantity and quality of flowers available. When the colony no longer produces workers, the old queen will eventually die and newly emerged queens will mate with males and then disperse to found new colonies. During this extended flight that may last for up to two weeks she may make several stops to examine the ground for a suitable burrow. Mikkola (1984) reported that bumble bees may forage up to a distance of 80 km in Finland.

Figure 4. Life cycle of a typical bumble bee colony: 1. A queen emerges from hibernation in spring and finds a nest site, such as an abandoned rodent burrow. 2. She creates wax pots to hold nectar and pollen, on which she lays and incubates her eggs. 3. When her daughters emerge as adults, they take over foraging and other duties. 4. In autumn, the colony produces new queens and male bumble bees, which

leave to find mates. Newly mated queens hibernate and the rest of the bumble bees die. Figure reproduced from Mader et al. (2011).

Unlike all other bees, bumble bees are large enough to be capable of thermoregulation, which allow them to maintain their foraging activities for longer periods of the day, but also to occupy regions with more extreme latitudes and temperatures compared to other bees (Heinrich 1979). Bumble bees may continue to forage when temperatures are below freezing even in inclement weather (Heinrich (1979).

Queens end the year by locating a sheltering burrow, where they may spend the winter months under cover. Where nesting habitat is scarce, bumble bee species having queens that emerge early (mid-March) in the season like B. vosnesenskii which co-occurs with the later emerging B. occidentalis, may be able to monopolize available nest sites and reduce the chances of success for bumble bee species emerging later. Western bumble bees have a short proboscis or tongue length relative to other co-occurring bumble bee species, which restricts nectar gathering to flowers with short corolla lengths and limits the variety of flower species it is able to exploit. Western bumble bees have been observed taking nectar from a variety of flowering plants, including Aster spp., Brassica spp., Centaurea spp., Cimicifuga arizonica, Corydalis caseana, Chrysothamnus spp., Cirsium spp., Cosmos spp., Dahlia spp., Delphinium nuttallianum, Erica carnea, Erythronium grandiflorum, Foeniculum spp., Gaultheria shallon, Geranium spp., Gladiolus spp., Grindelia spp., Haplopappus spp., Hedysarum alpinum, Hypochoeris spp., Ipomopsis aggregata, Lathyrus spp., Linaria vulgaris, Lotus spp., Lupinus monticola, Mentha spp., Medicago spp., Melilotus spp., Mertensia ciliata, Monardella spp., Nama spp., Origanum spp., Orthocarpus spp., Pedicularis capitata, P. kanei, and P. langsdorfii, P. groenlandica, Penstemon procerus, Phacelia spp., Prunus spp., Raphanus spp., Rhododendron spp., Salix spp., Salvia spp., Solidago spp., Symphoricarpos spp., Tanacetum spp., Taraxacum spp., Trifolium dasyphyllum, Trichostema spp., Trifolium spp. and Zea spp. (Evans et al. 2008).

Effects of the Alternatives

Key Indicators for Effects Analysis Include:  continuous access to flowering plants from spring through autumn  potential nesting habitat, including rodent burrows  pesticide use during the project

Current Condition of the Habitat Factors in the Analysis Area:

Western bumble bee (Bombus occidentalis) was only recently added to the Modoc National Forest list of Sensitive species on June 30, 2013. Casual sightings of bumble bees on the Warner Mountain Ranger District have taken place, but identification of species and detailed observations have not yet been undertaken by district personnel. For the purpose of this analysis, presence of the western bumble bee is assumed, but unconfirmed, on the project area.

Of the 25,276 acres on the project area, 100 percent of the project area is composed of wildland habitats for which western bumble bees are adapted.

No commercial crops, which employ domesticated pollinators, are grown adjacent to the project area, thus limiting the potential for disease transfer to bumble bees as outlined by Furst et al. (2014).

Also, no herbicide or insecticide use is proposed as part of this project. The Modoc National Forest does not use insecticides in routine forest and rangeland management.

General Discussion of the Range of Actions Proposed for this Project The management actions proposed for this project include thinning of conifers, prescribed burning, road construction and reconstruction, fuel break establishment and maintenance, planting, and weir repair (see Proposed Action in the Lassen 15 Restoration Project Environmental Assessment).

Vegetation Management General discussion The plant and animal communities present on the project area evolved with wildfire. Therefore, disturbances to vegetation, particularly the understory vegetation, were relatively frequent natural occurrences. Wild fire typically removes much of the existing understory vegetation during the year it occurs, followed by years of no fire during which vegetation can regrow and recover.

Alternative 1 - (Proposed Action)

Direct and Indirect Effects: There are many potential beneficial impacts to western bumble bee habitat by implementation of alternative 1. Opening forest canopies through application of thinning and prescribed burning is expected to benefit flowering plants by allowing more sunlight to reach the forest floor, reducing competition from trees for water and nutrients, and reducing the quantity of needle cast and duff on the soil surface. Nutrients released by prescribed burning may fertilize flowering plants, resulting in increased floral resources available to bumble bees. Also, ground disturbance caused by thinning, road reconstruction,

6 and fuel break activities would probably favor pioneering species of flowering plants, thus providing additional floral resources for western bumble bees.

Densities of burrowing rodents in the project area are expected to respond positively to increased abundance of understory plants in the years following thinning and prescribed burning. Due to reduced canopy cover, needle cast and reduced competition for sunlight, soil moisture and nutrients, understory plants including grasses and flowering plants are expected to provide increased food supplies for rodents. As a result, the number of rodent burrows which provide potential nesting sites for bumble bees should increase.

Planting activities would have a minimal effect on floral resources, due to limited amount of ground disturbance associated with the activity.

Road re-construction would have no effect on floral resources since there are no flowers growing within the road prisms. Road construction would have a minor effect to floral resources due to limited amount of disturbance.

The management activities proposed for this project and the reasonably foreseeable activities on adjacent lands would follow sequences of short-term disturbances followed by years of no impacts. This would be similar to the sequence of natural fire impacts.

Potential negative impacts to western bumble bee habitat would include: Some flowering plants may be damaged or killed during thinning, prescribed burning, road reconstruction and fuel break establishment and maintenance. However, these negative impacts would be limited to the growing season in which the treatment activities take place. In subsequent growing seasons, flowering plants in the impacted areas would recover, reoccupy disturbed areas and invade sites previously dominated by trees or other species.

Cumulative Effects of Alternative 1 (Action Alternative):

Past and present activities affecting the project area include: grazing by cattle, timber harvest, forest thinning, prescribed burning, fuelwood gathering, dispersed recreation, suppression of wildfires, and obsidian mining (Table 1). The cumulative effects analysis area includes the project area and a 3-mile buffer around the project area. The cumulative effects listed date from 2004. Future impacts are anticipated during the coming decade.

Table 1. Forest management activities for the Lassen 15 Restoration Project Area from 2004 through most recent reporting period. Year Activities Acres 2004 Prescribed Burning 434 2005 Prescribed Burning 486 2006 Prescribed Burning 139 2007 Thinning/Tree Planting 214 2008 Thinning 12 2010 Tree Planting 25 2011 Thinning 677 Ongoing (all years) Cattle Grazing 25,276 Ongoing (all years) Obsidian Mining; Mine Protection & Safety 31

Vegetation Management - Timber harvest and prescribed burning have occurred on the project area, which consists of ponderosa pine, eastside pine, white fir, and mixed conifer stands. Past timber harvest and prescribed burning appeared to release understory vegetation, especially Ceanothus velutinus. According to various websites, bees appear to use the flowers of this species. Therefore, timber harvest and burning have increased foraging opportunities for bees within the analysis area.

It is anticipated that the thinning and prescribed burning proposed in the Lassen 15 EA would cause the same long-term increase in understory plants, due to decreased competition from trees for sunlight, soil nutrients and soil moisture. Although short-term disruption of floral resources could result from project activities, recovery would generally occur within one growing season.

Firewood cutting is not anticipated to affect bumble bees, since they do not use snags for nesting. In addition, fuelwood cutting on the project area is limited by distance from population centers and therefore is discountable.

Thinning and prescribed burning have been proposed to make the project area more suited to the beneficial effects of natural fire and more resistant to wildfire, insect outbreaks and disease. The proposed treatments and the potential return of natural fire would stimulate floral resources important to bumble bees. Therefore, vegetation management activities proposed under the Lassen 15 EA are expected to have beneficial cumulative effects.

Fire Management – A combination of factors including fire suppression has allowed increased stocking of conifers on the project area. Consequently, there is a decrease in the floral resources available to bumble bees. Therefore, fire suppression has had negative effects on potential bumble bee habitat. However, the forest restoration measures proposed in this project would help reverse the decrease in floral resources. Therefore, the activities proposed in the Lassen 15 EA would have beneficial cumulative effects with respect to fire suppression.

Grazing - Seasonal livestock grazing permitted under Forest Standards results in minor disturbances to the shrub canopy layer and reduction in herbaceous materials. The impact on bee foraging opportunities from managed, rotational grazing on the analysis area has not been quantified, but is unlikely to limit the distribution of bumble bees. Cattle grazing on significant portions of the project area is very light or non- existent, due to dense brush and difficult terrain. Bumble bees forage on the flowers of various woody plants; thus, the dense stands of shrubs on the project area would be available as foraging opportunities for bees in addition to herbaceous plants. Therefore, livestock grazing would provide no negative cumulative impacts with respect to the implementation of activities proposed in the Lassen 15 EA.

Special Uses - Obsidian mining is permitted under the Warner Mountain Obsidian Management Plan. Abundant obsidian in the project area has attracted both commercial and recreational miners. One obsidian mine, the Lassen Creek Rainbow Mine (Rainbow), is located within the Lassen 15 Project area. Authorized mining activity occurs from May 1st to November 1st annually. Mining activity is a combination of commercial and personal use within the specifically delineated mining area. Excavation and removal of obsidian is done only with the use of non-mechanized hand tools. Historically, the Rainbow has 2 to 3 commercial operators that would account for up to 3 vehicles and perhaps 6 individuals for days at a time and periodically throughout the authorized period. Because Rainbow is on a major travel way to Lassen Creek Campground, recreational/personal use obsidian collection can account for several small family groups at the mine during any summer week.

Three other obsidian mines are located within 3 miles of the Lassen 15 Restoration Project analysis area. They are the: Middle Fork Davis Creek Mine, Obsidian Needles Mine and the Pink Lady Mine. All the obsidian mines operate under the Warner Mountain Obsidian Management [Plan], which authorizes obsidian mining, as well as resource and safety protection measures that can be used at the mine sites.

Obsidian mining has little or no impact on existing tree canopies, but introduces human presence and disturbance to the project area. However, the obsidian mines are small in size accounting for only 14.8 acres (less than 1/10th of 1 percent) of the 25,276 acres on the project area. There is no anticipated decrease in area for potential burrows and no significant decrease in floral resources from mining. Therefore, there are no cumulative effects from Special Uses with respect to the Lassen 15 EA.

Recreation - Dispersed recreation is focused along Lassen Creek and at the obsidian mines. Due to the low use of meadows and other habitats rich in flowers, recreation would not contribute to cumulative negative effects to potential western bumble bee habitat.

Noxious Weed Management - Invasive plants may be treated with either herbicide or hand grubbing according to the Modoc National Forest Noxious Weed Treatment Project standards and guidelines; however, no herbicide treatment is planned currently within the project area. Treatments are typically small in size and carefully prescribed to minimize potential impacts. Some noxious weeds are used as food sources by bumble bees. Conversely, the effect of not treating the habitat could cause a significant decrease in the amount of native floral resources for bumble bees. Although there may be nominal negative impacts to floral resources by the treatment of noxious weeds, the magnitude would depend on the species of noxious weeds and the plants that replaced them after treatment.

Road Management - Road designation and maintenance activities occur within road prisms, which do not have flowers and are not used for burrowing. Therefore, road management is not expected to affect bumble bee habitat.

Climate Change - Bumble bees are generalist foragers (The Xerces Society, 2015). As such, they use a wide variety of floral resources over the course of a growing season. This ability would likely allow them to adapt to changes in floral resources that may take place as a result of climate change.

To summarize, the contribution of Alternative 1 to cumulative effects to the western bumble bee would be low considering all of the past, present and foreseeable actions in and adjacent to the Lassen 15 Restoration Project area.

Alternative 2 – (No Action)

Direct and Indirect Effects: Potential negative impacts to western bumble bee habitat of Alternative 2 are as follows. There would be a continued increase in tree canopy cover in the absence of thinning and prescribed fire. A combination of this and the inclusion of fire suppression has allowed increased stocking of conifers on the project area. Consequently, there is a decrease in the floral resources available to bumble bees.

Also, there would be no stimulation of understory vegetation without proposed thinning and burning to release nutrients.

Potential beneficial impacts to western bumble bee habitat of this alternative would include no damage to floral resources due to thinning, prescribed burning and fuel break establishment during the season of treatment.

Cumulative Effects of Alternative 2 (No Action Alternative):

Past and present activities affecting the project area include: livestock grazing, timber harvest, forest thinning, prescribed burning, fuelwood gathering, dispersed recreation, suppression of wildfires, and obsidian mining. The same cumulative effects analysis area and timeframe used for the Action Alternative was used for this Alternative as well.

No Lassen 15 Restoration Project treatments would take place resulting in no beneficial impacts to flower resources within the project area.

In the absence of thinning and prescribed burning, there potentially would be an increase in the potential for wild fire to occur within the analysis area. Continued fire suppression would also allow for increased tree canopy, which would reduce understory flowering plants.

If a subsequent wild fire did occur, there would be a short term decrease in floral resources until plant re- growth occurred, long-term there would be a substantial increase in flowering plants. That would in turn provide potential increased suitable bumble bee habitat.

Firewood collection would have no effect on bees, since they do not use snags for nesting.

Due to the light grazing over the majority of the project area and the presence of dense brush (while serving to impede cattle movement provides foraging opportunities), it is anticipated that continued grazing would not have a negative cumulative effect with respect to the No Action Alternative.

Obsidian mining, recreation, road maintenance, and noxious weed treatments would continue to have minimal impacts to bumble bees, due to the localized nature of all of these activities.

DETERMINATIONS

It is my determination that the proposed actions for the Lassen 15 Restoration Project and the no- action alternative “May affect individuals, but is not likely to result in a trend towards federal listing or loss of species viability” for western bumble bee.

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