Providing foraging resources for bumblebees in intensively farmed landscapes

Habitat loss and the intensification of farming practices have caused severe declines in the range and abundance of many bumblebee species in the UK. This study examines the long-term effectiveness of four different management strategies to enhance and restore bumblebee foraging habitat on arable field margins in two regions with markedly contrasting landscape structure, farming systems and amount of semi-natural habitat. Bumblebees were monitored on 120 field margins in July and August, together with estimates of flower abundance and the vegetation composition. There were no differences in the abundance and diversity of the bumblebee assemblage between the two regions (East Anglia and the West Midlands), despite a greater abundance of flowers and flowering species on the lighter soils of the West Midlands. Very few bumblebees were recorded on intensively managed cereal field margins due to the lack of dicot species. Conservation headlands supported a significantly greater number of flowering dicots, but the majority of these were annuals which did not provide good forage for bumblebees. From an agronomic and ecological perspective, the removal of field margins from the cropping system was the best strategy for providing foraging habitat for bumblebees. Non-crop habitat resulting from natural regeneration provided good foraging habitat for bumblebee species, but most of the key forage species were pernicious weeds of agriculture (Cirsium spp.). Sowing non-crop field margins with wildlife seed mixtures had the potential for providing the best foraging habitat for bumblebees, so long as preferred forage species were introduced (e.g. Trifolium pratense). Further research is required to refine and target this management prescription for bumblebee conservation in the wider countryside.