Western bumblebee populations suffering alarming declines, study shows
The Western bumblebee is in precipitous decline, a new study shows, and researchers predict the species could all but disappear from parts of the American West by the 2050s.
Across the Western bumblebee's range – from the Black Hills of South Dakota to the West Coast and from Arizona up through Canada – populations declined 57% from 1998 to 2020, according to the study. It was published last month in the journal Proceedings of the National Academy of Sciences.
“So on average, across the species range in 1998, if you were to go to 10 random locations, we would expect to see the species in about five of those,” said William Janousek, a biologist with the U.S. Geological Survey and the study's co-lead author. “And by 2020 it was about 2 in 10 .”
The authors describe the dramatic decline of the generalist species as "a bellwether for loss" across the many species sensitive to environmental changes around the world.
In the Mountain West region, Janousek and fellow researchers found population declines ranging from 15% in the Greater Yellowstone Ecosystem to 83% in the Madrean Archipelago ecoregion, which spans parts of New Mexico and Arizona. The Southern Rocky Mountains saw a 72% drop, the Colorado Plateau and Wyoming Basin ecoregion 63%, and the Northern Rocky Mountains 37%.
The researchers largely attribute the declines to increasing temperatures and drought, which partly explains the wide variations across Western North America. They also point to a certain class of insecticides called neonicotinoids. The study includes a subset analysis showing that, from 2008 to 2014, there were 35% less bees in the areas where neonicotinoids were applied. As its application increased, so too did the extent of decline. Yet that analysis suggests increasing temperatures have an even greater effect.
The Western bumblebee's outlook will only become more dire, according to the study's projected future scenarios. Under its "severe" scenario, by the 2050s, the researchers predict declines from 51% to 97% in all the areas it occupies.
The loss of bees has huge ecological and economic impacts. Bees pollinate 85% of flowering plants – plants that wildlife rely on for their food.
“So they’re really like a linchpin in an ecosystem because they help plants then transfer those resources to other species,” Janousek said. “And so as you start to lose pollinators from ecosystems, you could see that system break down.”
These bees also pollinate our crops. In the U.S., the annual production value of wild pollinators has been estimated at more than $1.5 billion.
The Xerces Society for Invertebrate Conservation's website offers information on how individuals can help wild bees, including lists of beneficial plants, which pesticides to avoid, and how to make bee nesting sites.
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