Reducing ploughing promotes ground-nesting flying insects

Many flying insects, such as bees, wasps, and hoverflies, live aboveground, but depend on soil for nesting, development, and overwintering. In agricultural landscapes, soil is managed for production and therefore frequently subjected to disturbances such as ploughing. The impacts of ploughing on flying insects that spend part of their life cycle belowground remain largely unknown. To investigate the effects of ploughing on ground-nesting flying insects, we conducted a two-year field experiment in flower strips subjected to different treatments, ranging from annual ploughing to four years without ploughing. Insects emerging from the soil were sampled using emergence traps, allowing a direct assessment of their response to ploughing at different frequencies. For each treatment, we measured insect biomass, abundance, and body size. We found that ploughing substantially reduced flying insect biomass. When sites were left unploughed, biomass increased rapidly, particularly during the first years of recovery. However, regardless of the time since the last disturbance, ploughing always reduced insect biomass to similarly low levels, driven primarily by declines in the abundance of large insects. Our findings highlight that even moderate reductions in ploughing frequency, for example, only every second year, can benefit ground-nesting flying insects and point to the potential for incorporating reduced ploughing frequencies into agricultural management and agri-environmental schemes.