Bending the curve against insect declines - what can farmers do?

Land-use intensity, and hence farming intensity, is discussed as one of the major drivers of insect biodiversity change. However, working against insect declines requires action from key stakeholders such as farmers.

Collaborating with several networks of farmers across multiple years across a range of European countries, we measured biomass, abundance and species composition of insects in response to (i) pesticide reduction (insecticides and herbicides) (ii) on-farm biodiversity enhancement measures (such as in field or adjacent flowering strips) and (iii) crop identity under real-world farming conditions. Farmers, farmer associations and industry stakeholders were included in the design and implementation of biodiversity assessments and crop fields were managed according to conventional or organic practices. Insects were sampled using a range of methods, such as vane traps, pitfall traps, trap-nests for wild bees and antagonists, and soil cores for sampling of soil mesofauna.

We find that pesticide reduction and biodiversity enhancement measures (such as various flowering strip arrangements) consistently increase insect richness and biomass compared to controls, with largely additive effects of crop identity. Similar effects were found for belowground mesofauna that was, for example, enhanced in presence of flowering strips. Notably, our insect conservation measures were tailored to not compromise yield and to work under real-world everyday farming conditions.

In conclusion, farmers can contribute to "bending the curve" towards increasing insect diversity in farmland, for example by replacing insecticides or herbicides with measures of biodiversity conservation, without yield losses. Our findings pave the way for future policy development to arrive at more insect-friendly farming systems, with potential benefits in the heart of European high-intensity agriculture. One important component of such a strategy will be reduced pesticide use, for which mechanical weed control can be an economicaly viable strategy. If paired with other conservation efforts, e.g. on grassland or in nature reserves, a holistic approach to insect biodiversity protection in European agriculture can be achieved.