Temperature changes have harmed the majority of bumble bee species over the last 120 years, according to new research published this week in Biology Letters. The researchers note that temperature changes had a greater negative impact than other factors such as precipitation or floral resources.
"Bumble bees are important pollinators of both wild plants and crops used by humans. That is why we must devise conservation strategies that take into account the future effects of climate change on bee populations "Hanna Jackson, a Masters's student in biological sciences at Simon Fraser University, led the study.
Jackson and her colleagues examined an existing dataset containing records on 46 bumble bee species from 1900 to 2020 in North America. They developed two occupancy models, one for time and one for environmental factors, to estimate the effects of climate and land-use variables on species occupancy, which is a measure of where species are found. They discovered that six bumble bee species declined over time, 22 increased, and the remaining 18 remained stable.
They observe that, on average, temperature and precipitation increased between 1900 and 2020 during the post-industrial revolution period. Temperature changes primarily harmed bumble bees, with 37 of the 46 species experiencing greater declines or less positive increases in occupancy as a result of observed temperature changes compared to if the temperature had remained constant.
Importantly, nine bumble bee species declined in response to changing temperatures within their ranges. The team found no patterns in the other factors studied, such as precipitation, and only one species declined due to a lack of floral resources.
In fact, both floral resources and precipitation produced conflicting results. Changes in precipitation or floral resources impacted roughly half of the bumble bee species negatively, while the other half positively.
As a result, researchers conclude that changing temperatures are a major environmental factor driving changes in the composition of bumble bee communities.
"Because bumble bee species' future responses to land-use and climate change are likely to vary," Jackson adds, "conservation action should prioritize individual species, taking into account their unique climate and habitat preferences."
Pollinator Partnership, Xerces Society for Invertebrate Conservation, and the Department of Biological Sciences at the University of Southern California are among the study's collaborators.
Reference: DOI: 10.1098/rsbl.2021.0551