Road verges miss half of wild bee species, study reveals nature conservation gap
A Swedish study found that road verges, often promoted as pollinator habitat, actually exclude 61% of local bee species—particularly those that nest in cavities rather than soil. The finding challenges landscape management strategies and suggests policymakers need species-specific approaches to preserve pollination services critical to agriculture and food production.
Originaltitel: Trait and habitat filters shape absences of wild bee and butterfly species from road verges
Road verges can provide resources for pollinating insects, but it remains unclear if these resources are accessible to all species, or if some ecological traits can prevent certain species from using road verge habitats. We sampled wild bees and butterflies in 37 road verges in southern Sweden, with contrasting mowing regimes and along a gradient of traffic intensity. We compiled data on the pools of the regionally occurring species of wild bees and butterflies, and on ecological traits related to body size, feeding specialization and nesting habitat or overwintering stage. First, we tested if any of the selected ecological traits explained why some species were absent from road verges. Among the species that occurred in road verges, we then tested how the ecological traits influenced their response to management regime, verge width and traffic intensity. Along 7400 m of road verges, we observed 39% of bee species and 43% of the regionally occurring bee and butterfly species. Cavity-nesting bees were more likely to be absent from road verges than soil-nesting bees, but none of the ecological traits explained which of the regionally occurring butterfly species were absent from road verges. Among solitary bee and butterfly species that occurred in road verges, wider road verges reduced the absence probability more in dietary specialists than in generalist species. In bumblebees, wider road verges reduced the absence probability more in small-bodied than in large-bodied species. Our results indicate that road verges are suitable habitats for many but by far not all bee and butterfly species, and that certain species are prevented from using road verges because of their ecological traits. This needs to be considered when road verges are designed or managed to promote pollinating insects or biodiversity.