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UBC Theses and Dissertations

Evaluating field margins for wild bee conservation at the farm- and landscape-scale in the Agricultural Land Reserve of Delta, British Columbia Clausen, Martina


Wild bees provide essential pollination service to both agricultural crops and wild flowering plant species. The decline of wild bee species has been associated with a number of different threats, primarily the loss of natural habitat. The Delta Farmland & Wildlife Trust (DF&WT), a non-profit conservation organization, incentivizes farmers to plant hedgerows consisting of native shrubs and trees on the edge of their production fields, mainly to create habitat for wildlife in the Agricultural Land Reserve (ALR) of Delta, British Columbia. In this study, the value of DF&WT’s planted hedgerows was evaluated as foraging habitat for wild bees at both the farm and landscape-scale. During the summers of 2015 and 2016, I surveyed bees and flowers in planted hedgerows, as well as the two other most dominant field margin habitats, remnant hedgerows and grass margins. The relationship between floral resources and bees, as well as bee-flower visitations was analyzed and compared among these three habitat types. These empirical data were then used to parameterize the Conefor model, to evaluate the network of field margin patches within the agricultural landscape for their relative importance in landscape connectivity for wild bees. Overall, wild bees collected from flowers and pan traps were significantly more abundant, species rich and diverse in grass margins compared to planted and remnant hedgerows. While the strongest relationship was found between floral abundance and bee abundance, it did not explain the differences between habitat types alone. Bee-flower visitation records revealed a preference for herbaceous species mostly found in grass margins while only few recommended plant species for hedgerow plantings were visited. The results indicate that grass margins could be a valuable alternative conservation approach or addition to woody hedgerows if properly planned and managed. Connectivity indices generated by Conefor identified four grass margin patches that most contributed to overall landscape connectivity for bees with different dispersal abilities. These results can be used to help improve field edge management and the spatial targeting of activities by the DF&WT to improve the conservation of wild bee species.

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