No protection from chemicals: Even in German nature reserves, insects are contaminated with pesticides – not a single one of the protected areas examined was unpolluted, as a study has now revealed. An average of 16 different sprays were found per animal, including herbicides, insecticides and fungicides. The insects had picked up these chemicals from fields up to two kilometers from the nature reserve’s border.
The decline is obvious: In the last few decades insect populations have declined sharply around the world. In Germany, as a result of this decline, the biomass of flying insects has been reduced by a good 75 percent in 27 years, and other arthropods have also become measurably less. As a result, the number of birds is also dwindling more and more – even their songs are already thinned out.
But what is the reason? Scientists have long suspected pesticides as well as habitat loss through agriculture. Because some of them, like the neonicotinoids, are suspected of being able to harm insects despite statements to the contrary.
Sample analysis in nature reserves
Further arguments for this suspicion are now provided by the data from Carsten Brühl from the University of Koblenz-Landau and his colleagues. For their study, they investigated over two years whether and to what extent insects caught in 21 German nature reserves are contaminated with pesticides. For the first time, the team not only determined this indirectly, via the pollution of the air and soil, but also directly analyzed the chemicals contained in the insects themselves.
This was made possible because the insects are caught in so-called Malay traps for the long-term project. The animals fly into a kind of net cage and fall into a container with alcohol. This not only preserves them, it also acts as a solvent for the pesticides. “With our method, 92 pesticides currently approved in Germany can be analyzed simultaneously in small quantities,” explains Brühl’s colleague Nikita Bakanov. Samples taken every two weeks from 2020 were evaluated.
Up to 27 pesticides at once
The analyzes revealed: In none of the 21 nature reserves examined were the insects free from pesticides. Instead, the researchers found an average of 16.7 different chemicals in the animals – the range ranged from seven to 27 jointly detected pesticides. “Our data clearly show that insects in nature reserves are contaminated with a cocktail of pesticides,” says Brühl.
This finding supports concerns that insects and other animals often ingest several pesticides and accumulate them in their tissues. This can then increase the harmful effect through interactions of the agents with one another and mutually reinforcing biological effects. Scientists have long suspected that this cumulative effect of the pesticides could be decisive for the decline in insects.
“If you consider that the risk assessment as part of the pesticide approval process assumes that insects come into contact with only one pesticide, it is obvious how unrealistic this assessment practice is,” says Brühl.
Of the 47 pesticides detected, 13 were herbicides, 28 were fungicides used against fungal attack and six were insecticides. The three weed killers metolachlor-S, prosulfocarb and terbuthylazine, as well as the fungicides azoxystrobin and fluopyram, were found at all sample sites and in all 21 protected areas examined. As the researchers explain, these agents are among the best-selling pesticides in Germany.
The scientists even detected the neonicotinoid thiacloprid in insects from 16 of the 21 nature reserves. This insecticide has been banned for outdoor use in the EU since summer 2020 because it harms bees and other pollinating insects. “The frequent occurrence of thiacloprid in our samples probably reflects that the farmers took the last chance to inject their stocks with it,” explain Brühl and his colleagues.
In order to enable farmers to do just that, they were given a transition period until February 2021 to “taper off” the means. But as the study shows, it is precisely this that led to the application of a particularly large amount of the harmful thiacloprid. “It therefore seems advisable not to allow such transition periods and to destroy the stocks rather than to release them despite the proven damaging effect,” the researchers state.
Exposure to surrounding fields
The pollution of insects in the middle of nature reserves raises the question of where their pollution comes from. In Germany, the use of pesticides is prohibited within protected areas. The research team has therefore combined its data with an ecological spatial analysis. “We wanted to find out where the insects ingest the pesticides,” explains co-author Lisa Eichler from the Leibniz Institute for Ecological Spatial Development in Dresden.
The evaluation showed that the source of the contamination is not the protected areas themselves, but the surrounding fields. “The flight paths of insects vary from less than a hundred meters to several kilometers,” explain the researchers. According to their data, the flight radius of the insects examined was on average two kilometers – and thus extend far into the conventionally farmed landscape.
Buffer zones necessary
According to Brühl and his colleagues, this demonstrates that improvements to the nature reserve areas urgently need to be made. Because so far most nature reserves in Germany have been rather small and have no buffer zone to sprayed fields – such fields often border directly on the protected areas. Based on their results, the scientists are calling for two-kilometer-wide buffer zones to be designated around the protected areas in order to better protect insects.
“Strictly protected habitats under EU law would then also be protected from the effects of pesticides in reality,” says Brühl. In such buffer zones, agriculture could then be practiced, but only according to the guidelines of organic farming and thus without pesticides. Since by the year 2030, according to EU regulations, 25 percent of the agricultural area should be organically farmed anyway, according to the resolutions of the traffic light coalition even 30 percent, this could be used for such buffer zones. (Scientific Reports, 2021; doi: 10.1038/s41598-021-03366-w)
Source: University of Koblenz-Landau