Background and Rationale
In recent years not only honey bee populations were troubled (Buczek, 2009), but also the less known wild bee species declined greatly (IPBES, 2016). Wild bees provide essential pollination services to crops as well as to wild plants (Kearns et al., 1998) and without those pollinators many plants would be reduced in their reproduction capability, food webs and therefore whole ecosystems would collapse (Christopher O’Toole, 2002). Facing many different threats such as pesticides, diseases and climate change (IPBES, 2016) a meta-analysis of studies evaluating those threats by Winfree et al. (2009) found that the loss of natural habitat was most significantly adverse to the abundance and diversity of bees.
By protecting and restoring natural habitat within agricultural landscapes both conserving wild bees and providing ecosystem services can be accomplished (Morandin and Kremen, 2013). Several countries have promoted various Agri-Environment Schemes that encourages the creation of flower-rich habitat in form of cover crops, field border plantings, buffer strips and hedgerows (Wratten et al., 2012).
The Delta Farmland & Wildlife Trust (DF&WT), a local non-profit conservation organization works closely with farmers to optimize the regional ecosystem services of agricultural landscapes. Their Hedgerow Stewardship Program introduces planted hedgerows onto farmland mainly to create habitat for wildlife in the Agricultural Land Reserve (ALR) of Delta, British Columbia.
For my thesis project, 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 incorporated into a landscape connectivity model that identified important field margin patches for the provision of floral resources and the maintenance of habitat connectivity in the landscape for wild bees.
The overarching goal of this research was to provide the DF&WT guidance for optimizing habitat conservation and restoration investments for wild bees at the farm- and landscape-scale.
The first objective was to compare different field margin habitats to identify floral characteristics of the habitats most likely to ensure bee abundance and diversity. By discussing the role and floral characteristics of field margins as a place where wild bees can thrive and adding information to bee-flower visitation, restoration measurements for local bee populations can be optimized.
The second objective was to identify field margin patches that are most critical for wild bee habitat connectivity and habitat availability within the ALR using the software package Conefor 2.6 (Saura and Torné, 2009). By shifting the focus of protection and restoration activities to the landscape-scale, the combined threats of habitat loss and fragmentation can be addressed.
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.
To summarize, my project provides data to identify floral characteristics of field margin habitats and their value for wild bees, informs efforts to preserve existing habitats and helps guiding spatial planning of priorities for habitat restoration that benefit wild bees, biodiversity and farmers.
The following students have assisted with this project:
- Paula Porto
- Katelyn Hengel
- Owen Page
- Alyssa Johnston
- Jenny Liu
- Tianyi Kou
- Chanel Lewis
- Courtney Bridge
Buczek, K., 2009. Honey bee colony collapse disorder (CCD). Ann. UMCS, Med. Vet. 64, 1–6. doi:10.2478/v10082-009-0001-x
Christopher O’Toole, 2002. Those other bees: changing the funding culture. Environment 37–40.
IPBES, 2016. Summary for policymakers of the assessment rep ort of the Intergovernmental Science – Policy Platform on Biodiversity and Ecosystem Services on pollinators, pollination and food production.
Kearns, C.A., Inouye, D.W., Waser, N.M., 1998. ENDANGERED MUTUALISMS : The Conservation of Plant-Pollinator Interactions 83–112.
Morandin, L. a., Kremen, C., 2013. Hedgerow restoration promotes pollinator populations and exports native bees to adjacent fields. Ecol. Appl. 23, 829–839. doi:10.1890/12-1051.1
Winfree, R., Aguilar, R., Vazquez, D.P., LeBuhn, G., Aizen, M.A., 2009. A meta-analysis of bees’ responses to anthropogenic disturbance. Ecology 90, 2068–2076.
Wratten, S.D., Gillespie, M., Decourtye, A., Mader, E., Desneux, N., 2012. Pollinator habitat enhancement: Benefits to other ecosystem services. Agric. Ecosyst. Environ. 159, 112–122. doi:10.1016/j.agee.2012.06.020