Study Finds “Cocktail” Pesticides Are Killing Bees At A Higher Rate

In many countries across the world, bee numbers are currently threatened. As pollinators, bee populations are incredibly important for ecosystems across the world and our own food supplies. A new analysis of 90 studies has found that “cocktails” of agricultural pesticides can kill twice as many bees. 

The bee population has long been suffering. Threats to their populations are numerous and include habitat loss, climate change, and aspects of agriculture such as chemical pesticides. Many bees also face poor nutrition due to lack of diverse food sources.

A 2021 One Earth study found that “approximately 25% fewer species were found between 2006 and 2015 than before 1990.” The report analyzed public records from the Global Biodiversity Information Facility over 100 years. 

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The report stated that “wild and managed bees are key pollinators, ensuring or enhancing the reproduction of a large fraction of the world’s wild flowering plants and the yield of 85% of all cultivated crops.”

According to National Geographic, research concluded that bees have seen their numbers dwindled – in North America, you are now nearly 50% less likely to see a bumblebee in any given area than you were before 1974.

The study, published by the journal Nature, found that the “cocktails” of agricultural chemicals or pesticides may have a synergistic effect on bee mortality. This means that the total number of bees killed from these combination pesticides is greater than the sum total of deaths caused by all of the separate chemicals individually. 

The study documented 356 total effects from interacting common bee stressors, such as chemicals or parasites. Each study possessed at least two harmful factors to bees. The study then concluded whether the combinations of stressors canceled the other’s effects out, added to the other, or combined to caused even more damage. Researchers found that when bees were exposed to several agrichemicals, the combination had a “synergistic effect” on mortality, while numerous stressors had effects that added to the other.

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Researchers have now argued that these commercial formulas, which contain multiple chemicals in “cocktails,” should require licences. 

Speaking to the BBC, University of Texas at Austin’s Dr Harry Siviter — the lead author of the study — said that “exposure to multiple pesticides is the norm, not the exception.” “If you have a honeybee colony exposed to one pesticide that kills 10% of the bees and another pesticide that kills another 10%, you would expect, if those effects were additive, for 20% of the bees to be killed,” Siviter stated, adding that a “synergistic effect” could produce 30-40% mortality.

“That’s exactly what we found when we looked at the interaction. So we really should consider the interaction between those chemicals. We don’t continue to monitor pesticides once they’re licensed for use, so we’re proposing post-licensing observations. If those pesticides [used in combination] harm bees, that harm is recorded.”

It is unclear why pesticides have such an effect on bee mortality. The study’s abstract explained that “all interactive effects on proxies of fitness, behaviour, parasite load and immune responses were either additive or antagonistic; therefore, the potential mechanisms that drive the observed synergistic interactions for bee mortality remain unclear.”

Other research has indicated that pesticides could weaken a bee’s immune system making them more susceptible to other pathogens or chemicals. Speaking to Popular Science, Elizabeth Nicholls, an ecologist studying bees at the University of Sussex, said that “it also might be that their detoxification pathways might be impaired if they’re being bombarded with lots of chemicals at one time.”

The declining bee population is cause for great concern and has been for some time. In the US, the effects of which can already be seen in threatened crop species such as cherries, blueberries and apples, all of which need be pollination for survival.