The value of two agri-environment scheme habitats for pollinators: annually cultivated and floristically enhanced grass margins

Abstract

We investigate the potential benefits to pollinators of two agri-environment scheme habitats, annually cultivated and floristically enhanced grass margins. The former encourages annual plant species whereas the latter targets the provision of perennial plants, both may benefit foraging pollinators, many of which have declined in the UK since the 1980s. We surveyed thirty cultivated margins and thirty floristically enhanced grass margins across the UK for pollinators, which included bumblebees Bombus spp., solitary bees and hoverflies Syrphidae. Pollinator abundance was then related to margin attributes such as age, width, soil fertility and adjacent habitat type. For cultivated margins we also investigated relationships with cultivation and rotation, and for floristically enhanced margins time cut. Plant preferences of foraging pollinators were recorded in 2019. On cultivated margins, target annual plants were frequently recorded on plots and were repeatedly visited by pollinators with management significantly influencing visitation rates. For example, plots which had been created with ploughing attracted fewer solitary bees and bees overall than those created with minimum tillage. Annually rotated cultivated margins were associated with lower flower abundance, broad leaved species cover and vegetation heights which resulted in lower total bee abundance. We therefore advise that cultivated margins be left in situ on farmland over longer periods. Older floristically enhanced grass margins became dominated by grass and contained fewer flowerheads to support foraging pollinators. Compared to those established via natural regeneration, sown margins were associated with increased bee and Syrphidae abundance, which is probably linked to the high flowerhead abundance and coverage of broad-leaved species on sown plots. Our pollinator foraging data from 2019 showed that tolerance of some agricultural weeds should be advocated. Our results highlight the complementary benefits of these agri-environment scheme habitats to pollinators. We suggest that where arable pollinator conservation is a priority both habitats be provided.