Abstract
Wild bees are abundant in agricultural ecosystems and contribute significantly to the pollination of many crops. The specialisation of many wild bees on particular nesting sites and food resources makes them sensitive to changing habitat conditions. Therefore wild bees are important indicators for environmental impact assessments. Long-term monitoring schemes to measure changes of wild bee communities in agricultural ecosystems are currently lacking. Here we suggest a highly standardized monitoring approach which combines transect walks and pan traps (bowls). The combination of these two methods provides high sample coverage and reveals data on plant-pollinator interactions. We point out that comprehensive methodical, biological and taxonomical expertise is mandatory. The suggested approach is applicable to diverse monitoring goals in an agricultural context e.g. the impact of land use changes as well as monitoring potential effects of GM crops on wild bees.