Increasing applied pesticide toxicity threatens plants and insects

A group of scientists from the University of Koblenz-Landau, Germany, has shown that for plants and insects the applied pesticide toxicity in agriculture has substantially increased between 2004 and 2016. In a paper published in the current issue of Science, the authors show that this pattern is even relevant in genetically modified (GM) crops that were originally designed to reduce pesticide impacts on the environment.

“We have taken a large body of pesticide use data from the US and have expressed changes of amounts applied in agriculture over time as changes in total applied pesticide toxicity,” says lead author Ralf Schulz, professor for environmental sciences in Landau. “This provides a new view on the potential consequences that pesticide use in agriculture has on biodiversity and ecosystems”.

The amount of insecticides used in US agriculture has decreased substantially by more than 40% between 1992 and 2016. Fish, mammals, and birds face lower applied toxicities than in the 1990s, because insecticide classes such as organophosphates, which show high vertebrate toxicity, are used less today. Aquatic invertebrates and pollinators, such as honeybees, yet experience the opposite: despite reduced applied amounts, applied toxicity for these species groups has more than doubled between 2005 and 2015. A shift in the insecticides used towards usage of pyrethroid and neonicotinoid insecticides is responsible for this trend.

The applied toxicity increases for herbicides as well, alongside the applied amount. In this case, terrestrial plants are facing the highest increase in applied toxicity. Plants and pollinators are ecologically strongly connected. Simultaneously increasing applied toxicities in both groups thus alert to potential strong overall negative effects on plant and insect biodiversity.

GM crops have been developed to reduce the dependency of agriculture on chemical pesticide use. The results of the new study, however, clearly reveal that even in the two most important GM crops in the US, corn and soybean, the applied toxicity increases, along with increasing GM adoption, at the same rates as for conventional crops.

According to the authors, the results of the study likely apply to many other regions dominated by modern agriculture, though often the data for a thorough evaluation of trends in applied toxicity are not publicly available. Ralf Schulz adds: “These results challenge the claims of decreasing environmental impact of chemical pesticides in both conventional and GM crops and call for action to reduce the pesticide toxicity applied in agriculture worldwide.”

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Bibliographical information

Ralf Schulz, Sascha Bub, Lara L. Petschick, Sebastian Stehle, and Jakob Wolfram (2021): Applied pesticide toxicity shifts towards plants and invertebrates, even in GM crops. Science; https://doi.org/10.1126/science.abe1148

Press contact:

Gerhard Lerch

Public Relations Department

Phone: +49 6131 37460-36

Email: glerch@uni-koblenz-landau.de

Professional contact:

Prof. Dr. Ralf Schulz

iES Landau, Institut für Umweltwissenschaften

Phone +49 6341 280-31327

Email: schulz@uni-landau.de

Background: University of Koblenz-Landau

As the second largest university in the state of Rhineland-Palatinate, the University of Koblenz Landau is one of the youngest universities in Germany. Since its foundation in 1990, it has developed into a research-oriented university with the profile areas of education, humanities, and environment. The courses offered range from education, humanities, culture, social and natural sciences to computer science in Koblenz and psychology in Landau. It is the only university in Rhineland-Palatinate to offer teacher training programs for all types of schools. In February 2019, the Rhineland-Palatinate state government decided to establish the Koblenz campus as an independent university and to merge the Landau campus with the TU Kaiserslautern to create a new technical university.

The number of students at the University of Koblenz-Landau has increased at an above-average rate compared to other state universities over the past decade. There are now about 17,000 students enrolled, about half of them in Koblenz and half in Landau. Nearly half of all teachers in Rhineland-Palatinate are trained at the university, but subject-related and interdisciplinary courses are also in high demand. In research, the university has proven successes in all three profile areas, including in coordinated funding programs of the German Research Foundation (DFG). In particular, the University of Koblenz-Landau took first place in the DFG ranking of education and educational sciences.

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