Data from: Targeted agri-environment schemes significantly improve the population size of common farmland bumblebee species

Changes in agricultural practice across Europe and North America have been
associated with range contractions and local extinction of bumblebees
(Bombus spp.). A number of agri-environment schemes have been implemented
to halt and reverse these declines, predominantly revolving around the
provision of additional forage plants. Although it has been demonstrated
that these schemes can attract substantial numbers of foraging bumblebees,
it remains unclear to what extent they actually increase bumblebee
populations. We used standardized transect walks and molecular techniques
to compare the size of bumblebee populations between Higher Level
Stewardship (HLS) farms implementing pollinator-friendly schemes and Entry
Level Stewardship (ELS) control farms. Bumblebee abundance on the transect
walks was significantly higher on HLS farms than ELS farms. Molecular
analysis suggested maximum foraging ranges of 566 m for Bombus hortorum,
714 m for B. lapidarius, 363 m for B. pascuorum and 799 m for B.
terrestris. Substantial differences in maximum foraging range were found
within bumblebee species between farm types. Accounting for foraging range
differences, B. hortorum (47 vs 13 nests/km2) and B. lapidarius (45 vs 22
nests/km2) were found to nest at significantly greater densities on HLS
farms than ELS farms. There were no significant differences between farm
type for B. terrestris (88 vs 38 nests/km2) and B. pascuorum (32 vs 39
nests/km2). Across all bumblebee species, HLS management had a
significantly positive effect on bumblebee nest density. These results
show that targeted agri-environment schemes that increase the availability
of suitable forage can significantly increase the size of wild bumblebee
populations.