Manage the agricultural landscape to enhance floral resources
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Managing landscapes to enhance nectar and pollen resources for flower-visiting insects is increasingly recognized as an important strategy to enhance the agricultural pollination service and to conserve pollinator populations. It could involve increasing the diversity or area of flowering crops or conserving aspects of the landscape, such as flower-rich meadows, woodlands or river banks, which provide important floral resources.
In Europe, recent research has shown that higher coverage of the mass-flowering crop, oilseed rape Brassica napus, in the landscape is associated with higher numbers of foraging worker bumblebees Bombus spp. at focal sampling points, but not with enhanced bumblebee reproductive success or colony densities (Westphal et al. 2003, Herrmann et al. 2007, Westphal et al. 2009). This work is not summarized by Conservation Evidence because the evidence is correlative, the area of flowering crops was not increased as a conservation measure.
Westphal C., Steffan-Dewenter I. & Tscharntke T. (2003) Mass flowering crops enhance pollinator densities at a landscape scale. Ecology Letters, 6, 961-965.
Herrmann F., Westphal C., Moritz R.F.A. & Steffan-Dewenter I. (2007) Genetic diversity and mass resources promote colony size and forager densities of a social bee (Bombus pascuorum) in agricultural landscapes. Molecular Ecology, 16, 1167-1178.
Westphal C., Steffan-Dewenter I. & Tscharntke T. (2009) Mass flowering oilseed rape improves early colony growth but not sexual reproduction of bumblebees. Journal of Applied Ecology, 46, 187-193.
Supporting evidence from individual studies
A replicated controlled trial in 2004 in thirty-two 10 km grid squares across England (Pywell et al. 2006) found the abundance of long-tongued bumblebees Bombus spp., mostly common carder bee B. pascuorum and garden bumblebee B. hortorum, recorded on trial field margins (various planting treatments, including sown grass and wildflower margins) was positively correlated with the total number of pollen and nectar mix agri-environment agreements in each 10 km square. There is no record of the numbers of long-tongued bumblebees in these grid squares before the agreements were implemented. Bumblebees were counted on a 100 x 6 m transect in each of 151 field margins, once in July and once in August.Study and other actions tested