Individual study: Patches of planted flowers attract bees and hoverflies and increase hoverfly numbers 50 m away, on intensive farmland in Gelderland and Utrecht, the Netherlands
Kohler F., Verhulst J., van Klink R. & Kleijn D. (2008) At what spatial scale do high-quality habitats enhance the diversity of forbs and pollinators in intensively farmed landscapes? Journal of Applied Ecology, 45, 753-762
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Plant dedicated floral resources on farmland
Kohler et al. (2008) planted 100 m2 patches of 17 perennial and annual flowering plant species at five locations on intensive farmland in the central Netherlands. They measured the abundance and diversity of bees during one summer at 10 sampling locations along a 1,500 m transect running away from each patch, and along five 1,500 m control transects. All the transects ran alongside ditches. Bee abundance and diversity were 60-80% higher than on control transects within the flower patches, but not anywhere else along the experimental transects. This suggests that patches of sown forage plants do not enhance numbers of bees in the surrounding landscape, at least in the first year. The lowest values for numbers of bees and bee species were recorded at the sampling point 50 m away from the flower patches.
Plant nectar flower mixture/wildflower strips
A replicated, controlled site-comparison study in 2005 in the Netherlands (Kohler et al. 2008) found the number of flowers was 10 times higher in plots sown (or planted) with 17 insect-pollinated plant species than outside the plots (approximately 4,650 vs 480 flowers/plot within/outside flower plots respectively). The number and diversity of bees (Apidae) and hoverflies (Syrphidae) was significantly higher (60-80% higher) in flower plots than on control transects. Outside the flower plots, hoverfly abundance was significantly higher 50 m away from the flower plots but not at any other distance. The lowest numbers of bees and bee species were recorded 50 m away from the flower plots. Seventeen species of annual and perennial plants were either transplanted or sown in fenced 10 x 10 m plots at five locations in intensive farmland. Hoverflies and bees were surveyed at 10 sampling locations along a 1,500 m transect running away from each flower plot, and along five 1,500 m control transects. All transects ran alongside ditches. Bees and hoverflies were sampled using window traps, yellow water pans and nets four times between June and September 2004.