Data from: Scaling up effects of measures mitigating pollinator loss from local- to landscape-level population responses

1. Declining pollinator populations have caused concern about consequences
for food production, and have initiated an increasing number of
initiatives that aim to mitigate pollinator loss through enhancement of
floral resources. Studies evaluating effects of mitigation measures
generally demonstrate positive responses of pollinators to floral resource
enhancement. However, it remains unclear whether this represents
landscape-level population effects or results from a spatial
redistribution of individuals from otherwise unaffected populations. 2.
Here we present a method for estimating landscape-level population effects
using data from commonly used standardized pollinator transect surveys.
The approach links local density responses of pollinators in both
mitigation sites and surrounding landscape elements to the area these
habitats occupy in mitigation landscapes as well as control landscapes to
obtain landscape-level population estimates. 3. We demonstrate the method
using data from a two-year study examining the effects of experimental
wildflower enhancements on wild bumble bees and solitary bees in Dutch
agricultural landscapes. The results show that conclusions based on local
responses may differ significantly from those based on landscape-level
responses. 4. Wildflower enhancements significantly enhanced
landscape-level abundance of both bumble bees and solitary bees. Bumble
bees showed a pronounced positive local density response in mitigation
sites and the surrounding landscape that was in line with significant
landscape-level increases in abundance. However, solitary bees showed no
local response to mitigation sites, and the landscape-level increases in
abundance only became apparent when the area of bee habitat was taken into
account. 5. Incorporating the area of both newly created and pre-existing
pollinator habitats into effect estimates accounts for density-dependent
processes such as dilution, spill-over and local concentration of
individuals. It therefore results in more reliable estimates of the
response to mitigation measures of pollinators, as well as other mobile
arthropod groups that are often being surveyed using transect surveys.