The decline of insects, and in particular pollinating insects, threatens ecosystems and economies around the world. The dimensions are staggering: between 1989 and 2016, the biomass of all flying insects in Germany decreased by 76 percent, according to the Krefeld study (2017). The ever-increasing use of pesticides in agriculture is believed to be the driver of this phenomenon. Glyphosate, the world’s most widely used herbicide, may be contributing more to this development than previously thought, according to a researcher Dr Anja Weidenmüller from the Cluster of Excellence “Center for the Advanced Study of Collective Behavior” at the University of Konstanz. According to the new study (published on 3 June 2022).
Biologists are studying the ability of bumblebee colonies to regulate the temperature of their brood. Bumblebee colonies that have enough nectar available as ‘fuel’ keep their young at a constant temperature of about 32 degrees. “Just as we humans keep our body temperature constant, animals in a colony collectively show homeostasis in the temperature regulation of their brood,” says Weidenmüller. This combined thermoregulation is of outstanding importance for colony development. It is only at such high temperatures that the brood develops rapidly from egg to bumblebee and from a queen to a colony of several hundred individuals. The present study shows a clear effect of glyphosate on the collective thermoregulatory capacity of bumblebee colonies.
Time pressure for bumblebee colonies due to lack of resources
“When resources become scarce, you see very clearly that the collective thermal behavior of colonies that have been chronically exposed to glyphosate is affected,” Weidenmüller says. “They can’t keep their kids warm for long.” This effect is the main result of her study, which she conducted together with four researchers from the University of Konstanz, the Max Planck Institute of Animal Behavior in Konstanz and the University of Otago, Dunedin, New Zealand. “Bumblebee colonies are under really high pressure to grow as quickly as possible within a short period of time,” Weidenmuller says. If they cannot maintain the required brood temperature, their brood will develop more slowly or not at all. This limits the growth of the colony. “Only when they reach a certain colony size during a relatively short growth period are they able to produce the sexually reproductive individuals of a colony, that is, the queen and the drone.”
reproduction in danger
In times of resource scarcity, however, glyphosate-contaminated bumblebee colonies are less able to keep their brood warm, if at all. Due to the predominant agricultural landscape in Germany, there are fewer wildflowers available to insects, resulting in increased resource depletion. “The combination of resource constraints in clean agricultural landscapes and pesticides can pose a major problem for colony breeding,” says Weidenmüller.
Rethinking the approval process for pesticides
“It’s worth a closer look,” Weidenmüller insists. So far, approval procedures only examine how many animals have died after 24 or 48 hours of exposure to a substance or after exposure to a substance. “Sublethal effects, i.e. effects on organisms that are not lethal but can be observed, for example, in animal physiology or behavior, can have a significant negative effect and should be taken into account when pesticides are approved in the future. Must go,” she says. , In their study, bumblebees exposed to glyphosate also lived an average of 32 days, thus reaching the average age of bumblebees.
According to information from the European Food Safety Authority (EFSA), glyphosate is currently approved for use in the European Union until 15 December 2022. The Glyphosate Renewal Group (GRG) applied for renewal in 2019.
In principle, Weidenmüller’s research approach can be applied to all insecticides. For many commonly used insecticides, such as other herbicides and fungicides, we still don’t know anything about their effects on wild bees and other pollinators, she says. In our discussion of future agricultural approaches, the testing procedures used to assess the risks associated with our heavy use of chemicals should be reconsidered.
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