Story at a glance
- New research underscores the negative effect of climate change on alpine bee populations.
- According to 60 years’ worth of data, bees in alpine regions are in an evolutionary rut, unable to adapt to warmer temperatures.
- This means bees from more southern regions can exploit resources alpine bees miss out on, contributing to the species’s eventual demise.
Efforts to protect at-risk bumble bee populations are not new, as declining numbers have been reported in several states.
However, new research out of Webster University in Missouri points to climate change as a likely cause for lower rates of bumble bees in alpine regions, or high-elevation areas above timberlines.
Writing in the journal Global Change Biology, researchers investigated “whether bumble bee responses generate mismatches with floral resources, and whether these mismatches in turn promote community disruption and potential species replacement.”
Bees are essential to both humans and the environment as their work contributes directly to food security. According to the United Nations Food and Agriculture Organization, one-third of the world’s food production depends on bees.
The alpine study began in 2012, and experts assessed bee population data from three peaks in the Rocky Mountains. Researchers also analyzed data on the species collected over 60 years and found the bees have a low tolerance for warming temperatures.
As the earth warms, bees from lower elevations thrive and could potentially displace these vulnerable organisms. This phenomenon would lead to extinction of the alpine bee in the near future.
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“We predict the local extinction of species in areas where the alpine bees can‘t migrate further upslope, where the weather is cooler and the growing season still remains short,” said study co-author Nicole Miller-Struttmann, an associate professor of biology at Webster University in a statement.
“They are not responding to the temperature changes fast enough because they are stuck in an evolutionary trap.”
Warmer spring temperatures also mean earlier flowering of the bees’ preferred resources, authors explained. These temperature range-stable alpine bees might fall behind range-expanding bees when it comes to pollinating, due to a mismatch in timing of these seasonal events.
In addition, because alpine regions are typically cold, summer flower growing seasons are short, while the alpine bees likely adapted to this shorter time by limiting their foraging activity and reproductive phase. Now that longer, warmer seasons are more common, the bees miss out on flowers at later times, researchers explained.
In contrast, lower elevation bees are more flexible with their schedules, as they’re accustomed to warmer weather and can exploit these missed resources.
“Results suggest that conversion of historic habitats for cold-adapted alpine bumble bee species into refugia for more heat-tolerant congeners is disrupting bumble bee communities at high elevations,” authors wrote, although precise mechanisms behind these shifts remain unknown.
The evolutionary history of alpine bees means they’re only able to collect nectar and pollen during a short window — which is the same normal growing season in high elevations recorded half a century ago.
“As the climate warms and becomes more variable, organisms specialized to past conditions are declining, be it bumble bees or penguins,” said co-author Candace Galen, professor emerita at the University of Missouri at Columbia.
“We are losing biodiversity at a rapid clip, and with it the ecological services including pollination services that enrich and sustain our lives.”
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