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Many bumble bee species have declined in recent decades due to changes in habitat, climate, and pressures from pathogens, pesticides and introduced species. The western bumble bee, once common throughout western North America, is a species of concern and is being considered for listing by the U.S. Fish and Wildlife Service under the Endangered Species Act.

Native bees are responsible for pollinating a large percentage of the fruits and vegetables in our grocery stores. Pollinators provide $20 billion of agricultural pollination services each year. Bumble bees also help to pollinate foods that feed wildlife, such as huckleberries that are a staple for grizzly bears and black bears.

Western bumble bee
Credit: Xerces Society/Rich Hatfield)

In a recent study, scientists estimated a 93% decline in the occurrence of the western bumble bee in the continental U.S. between 1998 to 2018. This estimate varied depending on location and other environmental factors. “While western bumble bees were only present in 6% of their former range in the continental U.S., their presence was greater at higher elevations and latitudes than other locations,” said USGS scientist and co-lead author Will Janousek.

However, only limited sampling has occurred in some places, including most of Alaska, northwestern Canada, and the southwestern United States. Scientists recommend a sampling plan and increased data sharing to address these gaps and best inform the ESA species status assessment. “We hope to work together to learn where populations might persist and how to best conserve this species,” said USGS scientist and senior author Tabitha Graves.

USGS scientists worked to streamline data collection and research to assist the USFWS in their upcoming ESA species status assessment. Researchers evaluated information gaps and priority topics for research for the western bumble bee. Priorities include increased knowledge of trends, basic information on several life-history stages, and improved understanding of the effects of stressors on population trends, especially the effects of pathogens, pesticides, climate change and habitat loss.

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USGS scientist Tabitha Graves collects western bumble bee samples in eastern Montana.
USGS scientist Tabitha Graves collects western bumble bee samples in eastern Montana. 

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