Bee populations in Pennsylvania are on the decline

Sampling near Penn State’s Fruit Research and Extension Center shows a decline in bee populations. The results of the study, published in Ecology and Evolution are worrying to researchers.

“Bees are one of the most important groups of pollinators, but previous research has found troubling declines among wild bees,” said study lead author Nash Turley, a postdoctoral scholar at Penn State. “For example, the range and abundance of some species have shrunk substantially, especially bumble bees in North America and Europe. Tracking changes in bee biodiversity is important for developing pollinator management plans that can help sustain wild plant communities and maximize crop yields.”

The researchers intended for their study to characterize bee community changes from 2014 to 2019 (the period when they sampled bees). Bees were collected continuously from eight sampling spots near four orchards from April to October of each year. 

“These orchards are in a landscape that has high diversity and abundance of native plants and pollinators,” said study co-author Professor David Biddinger. “Only about 8% of the landscape is active orchards, and all of them are successfully pollinated only by wild pollinators.”

Overall, 26,700 bees from five families, 30 genera and 144 species were collected, representing 33 percent of the bee species known to live in Pennsylvania. The researchers found that the composition of bees was different in almost every month. Abundance of individuals as well as species of bees increased from April to June, for instance.

These seasonal changes are important, according to study co-author Professor Margarita López-Uribe.

“These groups of bees provide unique ecological functions,” said Professor López-Uribe. “For example, many of the early emerging bee species are of critical importance for early flowering plants such as spring ephemeral wildflowers, and these bee-plant interactions may be particularly sensitive to disruptions from climate change. And many crops, such as apples and blueberries, rely on pollination by early emerging wild bees.”

Unfortunately, the researchers found that some of these bees are in decline. They determined that 26 of the bee species had stable populations over time, while 13 species showed a decline over time. This is about one-third of the species with good data.    

“Wild bee communities are diverse and dynamic, and little is known about what species or groups have the greatest conservation needs,” said Professor López-Uribe. “Our findings could help to quantify the effects that different aspects of environmental change have on bee communities and to identify species of conservation concern.”

Image Credit: Nash Turley/Penn State

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By Zach Fitzner, Earth.com Staff Writer