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Pesticide use has become more toxic to invertebrates

Even as farmers apply lower amounts of pesticides, their total toxicity has increased for pollinators and other invertebrates

by Katherine Bourzac
April 3, 2021 | A version of this story appeared in Volume 99, Issue 12


Structures of imidacloprid and bifenthrin.

Pesticide use in the US became significantly more toxic for invertebrates from 1992 through 2016 (Science 2021, DOI: 10.1126/science.abe1148). During this period, agriculture shifted away from carbamate and organophosphorus pesticides, which are toxic to birds and mammals, to pyre­throids and neonicotinoids (examples of each shown), which are far less so. The newer chemicals are more potent, which means farmers can apply much less pesticide per hectare to get the same results. Decreasing total pesticide mass doesn’t guarantee an environmental benefit, however, says University Koblenz-Landau ecotoxicologist Ralf Schulz, one of the leaders of the new study. His group drew on government data cataloguing pesticide use in the US. The researchers then used species-specific toxicology data to estimate the impact of real-world pesticide use on plants and animals. Even though toxicity fell for birds and mammals, toxicity for some plants and for invertebrates that live in the water and on land—including pollinators like bees—increased significantly. This trend holds true even for genetically modified (GM) crops designed to require less pesticide by making the crops themselves resistant to a particular pesticide. “We introduced genetically modified crops in order to reduce the amount of chemicals applied,” Schulz says. But, he adds, “there is not really a difference between GM and conventional crops.” His team sees the same increases in pesticide toxicity for these crops as for conventional ones, likely because farmers are applying increasingly toxic chemicals to compensate for emerging pesticide resistance.



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