Climate change is extending blooming seasons – and that could be bad news for important pollinators like bees.
Researchers at North Carolina State University studying the effects of earlier and longer-lasting blooming seasons found that, far from helping bees, they may actually be causing harm.
“We asked whether variation in snowmelt timing and summer precipitation directly affected bumble bee colonies and their survival, or if the snowmelt and precipitation effects on flowers were more important,” said Dr. Rebecca Irwin, who co-led the study. “It turns out that the effects on flowers played a more critical role in affecting bee populations.”
The researchers were specifically looking at the effects of climate change on three species of bumble bees that live at higher altitudes, Irwin said.
She and her colleagues studied in depth a collection of data gathered at the Rocky Mountain Biological Laboratory in Colorado over a period spanning more than 40 years. After analyzing the data, they used modeling to examine the effects of climate change on the blooming seasons and the bees that rely on flowers in the region.
The data showed that, when snowmelt comes early, blooming seasons start earlier and last longer, which sounds like a good thing for pollinators at first. But plants don’t actually produce more flowers, Irwin and her colleagues found. Instead, they stretch the usual number of blooms over a longer period of time, meaning that on a day-to-day basis there are actually fewer flowers for bees in search of food.
“Longer flowering seasons mean an increasing number of resource-poor days for bees, which means that bee abundance suffers,” Irwin said. “We found that bee abundance increased when there was more summer precipitation and shorter flowering seasons.”
The researchers plan to continue collecting and analyzing data on the three bee species, as well as expand to look at other species of pollinators.