It was almost exactly four years ago that the small Entomological Association in Krefeld became famous overnight. At that time, the predominantly volunteer employees managed to scientifically prove what had been nothing more than a bad feeling up until then: insects are dying in Germany.
In a new study, in which the entomologists from Krefeld were again involved, Carsten Brühl from the Institute for Environmental Sciences at the University of Koblenz-Landau is now investigating the causes of the loss.
The study that in the science journal Scientific Reports published, supports the long-held suspicion that the use of pesticides in intensive agriculture is one of the main reasons for the sharp decline in flies and butterflies, beetles, wasps, bees and other insects in Germany. In 2017, the entomologists from Krefeld showed that the mass of insects had decreased by an average of 76 percent since 1989.
As in the past, the entomologists were on the road again with their “Malay traps”. The tent-like structures in which flying insects get caught. The animals are then preserved in alcohol on site. For the current study, they set up the traps from April to October 2020 in various regions of Germany. All 21 locations examined were located in protected areas that belong to the European Natura 2000 system of protected areas.
A neonicotinoid, which had been banned for a long time, was also found at 16 locations
It is all the more frightening that the researchers were able to detect a whole cocktail of pesticides in all samples. To do this, they examined the alcohol in which they had preserved the trapped insects for 92 of the most common substances used in agriculture. According to the study, the pesticides discovered must come from the insects, as the alcohol is a solvent for many chemicals that are on or in the bodies of the animals.
According to the results, the insects in the protected areas were contaminated with an average of 16 different pesticides, at one location it was even 27. In total, the researchers were able to detect 47 different substances, including residues of the herbicides Metolachlor-S and Prosulfocarb. The fungicides azoxystrobin and fluopyram were contained in samples from all locations and the neonicotinoid thiacloprid, which is now banned throughout the EU, in 16.
It has long been known that useful insects also come into contact with pesticides that were actually developed to control pests. The same applies to the realization that the toxic substances do not stay on the field on which they are used, but spread into the environment.
Most studies on the spread of pesticides, however, focus on residues of these substances in bodies of water. How much insects themselves are contaminated with pesticides, however, has hardly been investigated so far and if so, then mostly only individual substances.
“Far too little is known about the combined effects of whole cocktails of different pesticides and their metabolites on insects,” the scientists write. According to the authors of the study, the fact that the toxic substances on insects could be detected in the middle of nature reserves can be explained by the fact that all the areas examined are close to fields that are intensively cultivated. “To this day, biodiversity-promoting agriculture without the use of pesticides is an exception both within and on the immediate periphery of the most valuable protected areas,” write Thomas Hörren and Martin Sorg from the Entomological Association in Krefeld in a statement.
In the opinion of the study authors, in order to at least reduce the pollution of nature reserves with pesticides in the future, at least buffer zones should be set up around such areas in which the use of pesticides is prohibited.