Bumblebee habitat restoration in the agricultural landscape

The response of foraging bumblebees to various restoration and management options for arable field margins is studied across a series of single and multi-site experiments. Bumblebee abundance is closely linked to flower abundance of suitable forage species, and to successional changes in availability of these both during the season and between years. Margins sown with a mixture of pollen and nectar-rich plants, such as Trifolium pratense, are shown to attract large numbers of bumblebees, including rare species. The analysis of pollen loads confirms contrasting forage plant preferences in Bombus pascuorum and Bombus terrestris, adding important information to that from transect counts on the functional value of introduced flower mixtures for local colonies. Widespread uptake of the Entry Level Environmental Stewardship scheme could therefore have rapid and positive effects on some species, but more diverse native plant communities may be required to provide a longer-lived forage supply to a greater range of Bombus species and other pollinators. The thesis concludes that although the total area of suitably managed habitat required to sustain populations is large, current AES prescriptions providing a combination of widespread, low cost and more targeted, specialist options for habitat creation are likely to significantly enhance the quality of the agricultural landscape for bumblebees. Future success will require close links between policy markers and ecologists, between the management of farmed land and protected semi-natural grasslands across Britain, and regular monitoring of the effects of habitat restoration on rare and common bumblebees and their interactions with other components of agricultural ecosystems.