Action: Provide grass strips at field margins for bees
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Three replicated controlled trials in the UK have monitored wild bees on uncropped grassy field margins. Evidence of the effects on bees is mixed. One trial showed that 6 m wide grassy field margins enhanced the abundance, but not diversity, of wild bees at the field boundary. One trial showed that 6 m wide grassy field margins enhanced the abundance and diversity of bumblebees within the margin. A third, smaller scale trial showed neither abundance nor diversity of bumblebees was higher on sown grassy margins than on cropped margins.
Supporting evidence from individual studies
A small replicated, controlled trial of field margin management options on two farms in North Yorkshire, England in one summer (Meek et al. 2002) did not find significantly more bumblebees on margins sown with tussocky grass than on naturally-regenerated margins or cropped margins. There were four replicates of each treatment.
A replicated, controlled trial of the 6 m wide grassy field margin agri-environment scheme option at 21 sites in England found no difference in the diversity of wild bees (sampled in the field boundary by walked transect and sweep netting) between paired control fields and fields with sown grassy margins (Kleijn et al. 2006).
The same study, reported elsewhere (Marshall et al. 2006), showed a significantly greater abundance of bees in boundaries of fields with sown grassy margins; 40% of the bees recorded were of one species, the red-tailed bumblebee Bombus lapidarius.
A replicated, controlled trial of the 6 m wide sown grassy field margin agri-environment option at 32 sites across England (Pywell et al. 2006) found that grassy margins had more species, and a higher abundance of foraging bumblebees, than conventionally cultivated and cropped field margins (on average 6-8 bees of 1.3-1.4 species per transect on grassy margins, compared to 0.2 bees of 0.1 species/transect for cropped margins). Older grassy margins, sown more than three years previously, did not attract more foraging bumblebees than those sown in the previous two years.
- Meek B., Loxton D., Sparks T., Pywell R., Pickett H. & Nowakowski M. (2002) The effect of arable field margin composition on invertebrate biodiversity. Biological Conservation, 106, 259-271
- Kleijn D., Baquero R.A., Clough Y., Diaz M., De Esteban J., Fernandez F., Gabriel D., Herzog F., Holzschuh A., Johl R., Knop E., Kruess A., Marshall E.J.P., Steffan-Dewenter I., Tscharntke T., Verhulst J., West T.M. & Yela J.L. (2006) Mixed biodiversity benefits of agri-environment schemes in five European countries. Ecology Letters, 9, 243-254
- Marshall E.J.P., West T.M. & Kleijn D. (2006) Impacts of an agri-environment field margin prescription on the flora and fauna of arable farmland in different landscapes. Agriculture, Ecosystems & Environment, 113, 36-44
- Pywell R.F., Warman E.A., Hulmes L., Hulmes S., Nuttall P., Sparks T.H., Critchley C.N.R. & Sherwood A. (2006) Effectiveness of new agri-environment schemes in providing foraging resources for bumblebees in intensively farmed landscapes. Biological Conservation, 129, 192-206