Local and landscape effect of maize cultivation on bee biodiversity and abundance - Using field trials of the engineered crop MON810 to study bees in the agricultural landscape

Abstract: Agricultural intensification has led to the homogenization of the landscape and the disappearance of diverse habitats with rich flower resources that are important for pollinating insects. The main insect pollinators, by far, are bees. And while honey bees (Apis mellifera) are the best known, there are also hundreds of other species of bees that contribute to pollination services. Due to their foraging behaviour, bees are exposed to many agricultural practices that are likely to influence their abundance and/or diversity. I studied bee diversity, abundance and temporal trends in maize in southern Sweden for three years as part of the EU FP7 research project AMIGA, “Assessing and Monitoring the Impacts of Genetically modified plants on Agro-ecosystems”. Few studies have addressed bee utilization of maize fields and my study is the first large-scale bee inventory of its kind in Sweden. Honey bees, bumble bees, and solitary bees have been analysed separately. My study quantifies the influence of landscape effects on bee abundance and diversity and possible effects of local management practice exemplified by use of the engineered crop MON810. I found no effect of the genetically modified maize on bee abundance and diversity in any of the three groups, which is in accordance with previous studies. There was a significant positive effect of the percentage of surrounding non-agricultural area on bumble bee and solitary bee abundance as well as on solitary bee species diversity. This effect was greater during certain months of the sampling. Bumble bee abundance and diversity were greater with increasing non-agricultural area in June. Solitary bee abundance was greater with increasing non-agricultural area especially in July. These results illustrate the importance of surrounding non-agricultural land for bee diversity and abundance spatially and temporally. The presence of bees in maize fields throughout the entire season suggest that bees might use these crop fields for other purposes than pollen collection, for instance passing through them on their way to other areas. But further studies need to address this topic and provide behavioural data throughout the entire season to confirm any other form of interaction. The discussion highlights the importance of diversifying landscapes and natural habitats for bees that are foraging in the surroundings of cultivated maize fields.