Bee population estimates bumbled, SFU researchers find 25 June

Simon Fraser University

Don’t bee-lieve everything you read; reports of the bumble bee’s death are greatly exaggerated. A new study from Simon Fraser University is adding to a growing body of work that suggests not all bee populations are in decline.

The plight of pollinators, such as bumble bees, has been the subject of high-profile studies, news reports, public awareness campaigns and corporate drives for years. One study reported that overall bumble bee populations have dropped 46 per cent in North America over the last century.

However, researchers at SFU have developed more accurate modelling that shows just a five per cent decline in North America overall. While some species of bees have seen alarming rates of decline, the findings, published in the journal Biological Conservation, suggest evidence gathering and modelling need to be improved so conservationists can prioritize the bee species most at risk.

“When we reconsidered the evidence, we found that it’s not all doom and gloom for bumble bees,” says Melissa Guzman, lead author of the paper and a postdoctoral fellow in the Department of Biological Sciences at SFU. “In a rare case of good news for biodiversity, we found there is no evidence of community-wide declines of bees. Many species are certainly declining dramatically, but many others seem to be doing fine.”

According to Guzman, scientists have had to rely on large datasets from museums, surveys and community science initiatives for their analysis of overall bee populations. But often the data is collected haphazardly and the analysis has focused on a limited number of bee species, without taking the ranges and detection records of other species into account. This has inadvertently led to reports that have over-estimated the decline of bee populations.

The estimates are especially skewed in North America, where historical data on bee visitation hasn’t been as reliable and consistent as in Europe. The new multi-species modelling done on European bumble bee populations was more in line with previous studies, but the estimated population decline is still lower than previously thought (six per cent instead of 17).

While researchers did not find major overall declines across all species, many individual species appear to be in trouble. One species of critically endangered North American bumble bee, B. bohemicus, is estimated to have seen a dramatic decline of 73 per cent based on the new modelling.

The research team also included SFU professors Leithen M’Gonigle and Arne Mooers, and graduate student Sarah Johnson.

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