No recovery in the biomass of flying insects over the last decade in German nature protected areas.

Five years after a German study on insect biomass described a multi-decade decline in nature protected habitats, the DINA (Diversity of Insects in Nature protected Areas) project has investigated the status of insects in 21 selected nature reserves across Germany in the years 2020 and 2021. We used the same methods and protocols for trapping and measuring the biomass of flying insects as in the earlier study. Across two vegetation periods, we accumulated a comprehensive data set of 1621 data points of two-week emptying intervals to evaluate the insect biomass along gradients from arable land into nature reserves through transects of Malaise traps. On average, we observed an increase in maximum insect biomass per day along the transect from the edge to the centre of the nature reserve. Overall, the measured insect biomass remained at low levels, consistent with previous findings from the years 2007-2016. There were no significant regional differences. The results show that protected habitats have higher insect biomass compared to farmland and are therefore essential for insects but are unlikely to be sufficient to sustain insect biodiversity. Further measures need to be taken for better protection and sustainment of insects, which fulfil key functions in all terrestrial ecosystems.

Direct pesticide exposure of insects in nature conservation areas in Germany.

In Germany, the decline of insect biomass was observed in nature conservation areas in agricultural landscapes. One of the main causal factors discussed is the use of synthetic pesticides in conventional agriculture. In a Germany-wide field study, we collected flying insects using Malaise traps in nature conservation areas adjacent to agricultural land. We used a multi-component chemical trace element analysis to detect 92 common agricultural pesticides in ethanol from insect traps sampled in May and August 2020. In total, residues of 47 current use pesticides were detected, and insect samples were on average contaminated with 16.7 pesticides. Residues of the herbicides metolachlor-S, prosulfocarb and terbuthylazine, and the fungicides azoxystrobin and fluopyram were recorded at all sites. The neonicotinoid thiacloprid was detected in 16 of 21 nature conservation areas, most likely due to final use before an EU-wide ban. A change in residue mixture composition was noticeable due to higher herbicide use in spring and increasing fungicide applications in summer. The number of substances of recorded residues is related to the proportion of agricultural production area in a radius of 2000 m. Therefore, a drastic pesticide reduction in large buffers around nature conservation areas is necessary to avoid contamination of their insect fauna.