BOWLING GREEN, Ohio — A recent study from Bowling Green State University shows U.S. bee populations are having a harder time surviving the rise of temperatures as well as increasing urbanization, mainly because of dehydration rather than overheating.
The multi-year study was led by Dr. Kevin McCluney, an associate professor of biological sciences at BGSU. He and his research team monitored the health and number of bees at 60 urban farms and gardens in 10 U.S. cities over the course of three years. It was funded by a $430,000 grant from the U.S. Department of Agriculture, according to BGSU.
“It is vitally important to understand the connection between the climate and pollinator health,” McCluney said in a release. “It’s estimated that the value of crops pollinated by bees is worth about $24 billion per year in the U.S. Bees are incredibly important to our food systems, which is why learning more about how bees are impacted by rising temperatures is crucial.”
Researchers studied the body temperature and hydration of dozens of bees species in urban heat islands in six states: Ohio, Arizona, North Carolina, Georgia, Colorado and Michigan. The study sampled more than 4,000 species nationwide.
With the data, researchers were able to establish the threshold of the bees at which they died from warming or dehydration. Through the data, they found that most bees in 10 major U.S. cities included in the study are at a greater risk of dying from dehydration than overheating as their body temperatures rise, which is something the researchers didn’t anticipate.
“Most bees are ectothermic, meaning their body temperature rises with air temperature,” McCluney said in a release. “Similar to humans, bees lose water as they get hotter, which can cause dehydration. This data will allow us to see where in the country pollinators are in peril and why they are at risk.”
McCluney added that many bee populations are also declining because of habitat loss, diseases and parasites, as well as pesticides being used on crops and other areas.
The bee species facing the harshest decline is bumblebees, which were almost nonexistent in Phoenix and Tucson in the study. They’re effective pollinators and are important for many plants that require buzz pollination, which is using vibrations to release pollen from flowers, the study explained.
Since 1850, Earth’s temperature has risen by an average of .11-degrees Fahrenheit each decade, which is about 2-degrees Fahrenheit in total, according to the National Oceanic Atmospheric Administration. 2023 ended up being the Earth’s warmest year on record. And according to Environment America, some bumblebee species have seen a population drop of up to 90% in the past two decades.
“As bee populations decline, as they might with urban heat islands, food becomes harder and more expensive to produce and quality diminishes,” McCluney said in a release. “Then the question becomes, ‘Are there other species of bees that can pick up the slack and pollinate without them?’”
The data overall helps researchers understand the dangers bees face as Earth's temperature continues to rise. The team is still researching if bees could have adverse health effects if they approach their dehydration thresholds.
