German researchers have found that when food for bumblebees is scarce, exposure to glyphosate can significantly impair bumblebees’ collective ability to maintain their hive temperature, having a negative physiological and behavioral effect on the insects. The study, Glyphosate impairs collective thermoregulation in bumblebees, is authored by Dr. Anja Weidenmüller from the University of Konstanz and is being published June 3 in the journal Science.
This research related to glyphosate, the most widely used synthetic herbicide in the world, is sure to be another tool used by those who speak out against many modern farming practices and blame agriculture for changes in bee populations over the years.
Maintaining hive temperature is critical for colony survival and is the most important factor in brood development. Bumblebee colonies that have sufficient nectar available as “fuel” keep their broods at a constant temperature of about 32 degrees.
“Just as we humans keep our body temperature constant, the animals in a colony collectively show homeostasis in the temperature regulation of their brood,” Weidenmüller said. This joint thermoregulation is of outstanding importance for colony development. Only at such high temperatures does the brood develop quickly from egg to bumblebee and the colony from a single queen to a colony of several hundred individuals.
While environmentally realistic exposure to glyphosate is not directly lethal to bumblebees, Weidenmüller noted, the current study shows a clear impact of glyphosate on the collective thermoregulatory capacity of bumblebee colonies. She said that the collective ability of the hive to maintain its needed temperature decreased by more than 25 percent during periods of resource limitation and amid exposure to glyphosate.
“Bumblebee colonies are under really high pressure to grow as quickly as possible within a short period of time,” Weidenmüller said. “Only when they reach a certain colony size during the relatively short growth period are they able to produce the sexually reproductive individuals of a colony, i.e. queens and drones.”
Could research like this be used to rethink the approval procedure for pesticides, at least in the European Union?
“It’s worth taking a closer look,” Weidenmüller said. So far, approval procedures only test how many animals have died after being fed or coming into contact with a substance after 24 or 48 hours. “Sublethal effects, i.e. effects on organisms that are not lethal but can be seen, for example, in the animals’ physiology or behavior, can have a significant negative impact and should be taken into account when pesticides are approved in future,” she says.
In her study, the bumblebees exposed to glyphosate lived an average of 32 days, thus reaching an average bumblebee age.