Crop-pollinator interactions in urban and peri-urban farms in the United Kingdom

Societal Impact StatementUrban food production could contribute towards sustainable food provision and would also deliver benefits to biodiversity and the health of urban residents. Many crops rely on insect pollination, but urban pollinator populations are under-studied. In this study, crop-pollinator interactions and pollination quality were quantified in urban allotments in the United Kingdom. A diversity of insects was observed visiting the flowers of food crops, with squash, cucumber and fruit trees attracting the most flower visitors. However, strawberry plants pollinated naturally by insects produced lower quality fruit than those receiving supplemental hand-pollination. Urban crop pollination could therefore be improved through the provision of food and nesting habitats for insects. Growing food in and around cities could be a partial solution to sustainably increasing food production in an urbanised world. Recent studies have shown that small-scale urban farms can be as productive, if not more so, than large-scale conventional farms. However, the question of which insects visit fruit and vegetable crops in urban areas and whether there are sufficiently large and diverse populations to provide adequate pollination to food crops has been little explored.Here we quantified plant-pollinator visitation networks in urban allotments in the city of Brighton and Hove, UK, to determine which insect groups visit commonly grown fruit and vegetable crops. We also conducted pollinator deficit experiments to determine whether there are sufficient pollinators in urban allotments to adequately pollinate two commonly grown insect-pollinated crops, strawberries (Fragaria x ananassa) and runner beans (Phaseolus coccineus).A broad range of insect-pollinated fruit and vegetable crops were grown in allotments and were visited by a diversity of insects spanning many taxonomic groups. We found little evidence that runner bean crop yields were limited by a lack of pollination; however, open-pollinated strawberry plants produced more 'unmarketable' fruit suggesting there is potential for improving the delivery of pollination to strawberries grown in urban areas.Our results suggest there are potential opportunities for expanding urban food production to the benefit of both people and biodiversity. We recommend that future work should also consider the effectiveness of different insect groups in pollinating the various crops grown in urban areas.