Gauging the effect of honey bee pollen collection on native bee communities

Authors: Cane, James; TEPEDINO, VINCENT - Retired ARS Employee

Submitted to: Conservation Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2016
Publication Date: 6/15/2016
Citation: Cane, J.H., Tepedino, V.J. 2016. Gauging the effect of honey bee pollen collection on native bee communities. Conservation Letters. 10(2):205-210. https://doi.org/10.1111/conl.12263.
DOI: https://doi.org/10.1111/conl.12263

Interpretive Summary: Mounting concern over pollinator decline has prompted policies and programs to conserve pollinators of crops and native plants. A recent Presidential Memorandum (2014) directed federal agencies to develop a Pollinator Health Strategy that benefits both managed honey bees and native bees. In devising policies to reverse or halt pollinator declines, we must avoid conservation programs that unintentionally benefit one pollinator group at the expense of others. Both honey bees and native bees require pollen, but its availability, along with nectar, is finite and thought to regulate wild bee populations more than any other factor. When commingled with large numbers of honey bees, native bee populations may suffer from intense resource competition. We address the long-standing and common practice of migratory beekeepers of placing their apiaries on public wildlands (e.g., U.S. Forest Service) to freely forage once their contracts to pollinate spring-flowering crops are fulfilled. We estimate the likely impact that the pollen removed from wildflowers by a honey bee colony has on solitary bee populations, in terms of progeny equivalents of an average solitary bee. We calculate that, over a three month period, the pollen pellets accumulated by a single hive of honey bees on public wildlands are enough to reduce native bee populations of average size by 100,000 progeny. Such an equivalence is needed by public land managers, who confront mounting demands by migratory beekeepers for insecticide-free, resource-rich habitats in practical locations to place their hives during the later summer months. We suggest thoughtful limits to apiary stocking on public lands, inasmuch as they collectively hold much of the remaining US native bee fauna, and highlight efforts and programs, such as the Conservation Reserve Program, that can provide more quality honey bee pasture on fallowed farmlands without adversely impacting our irreplaceable native bee populations.

Technical Abstract: The broad question --“Do honey bees compete with native bees?” -- has no singular answer for wildlands, being functions of: 1) the variable stocking densities of bees, and 2) unknowable carrying capacities of floral resources. The conventional approach, i.e. experimental demonstration of direct exploitative competition, remains hopelessly mired in arguments over experimental design, context-dependence and extrapolation from case studies to realistic temporal and spatial scales. We propose a different approach, casting wildland floral resources collected by a honey bee colony in terms of progeny equivalents of an average solitary bee. Some a metric is needed by public land managers, who confront mounting demands by migratory beekeepers for insecticide-free, resource-rich habitats in practical locations to place their hives during the later summer months. During three months, we calculate that the pollen pellets accumulated by a hive of honey bees in wildlands are enough to produce 100,000 progeny of a native bee species of average size. Analogous to the animal unit month (AUM) for livestock, a hive unit month (HUM) would thereby equal 33,000 native bee progeny. We suggest thoughtful limits to apiary stocking, therefore, on Western US public lands which collectively hold much of the remaining US native bee fauna. We highlight programs that can provide more quality honey bee pasture on grain fields of the Upper Midwest fallowed under the Conservation Reserve Program.