Flower-rich road verges increase abundance of flower visitors in the surrounding landscape

Abstract

Flower-visiting insects and the plants that depend on them are declining due to habitat loss and deterioration. Road verges, which often provide abundant floral resources, are gaining attention for their potential conservation value, as they can support a high abundance and diversity of flower-visiting insects. Thereby, flower-abundant road verges may benefit pollination in surrounding landscapes. However, the potential negative effect of traffic on this benefit remains unexplored. We addressed the research gap using potted wild strawberry plants (Fragaria vesca, variety ‘Rügen’), placed at 20 m and 80–100 m distance from road verges along roads with varying traffic intensity (around 100–5500 vehicles per day). We found that floral abundance in road verges enhanced the number of flower visitors to strawberry plants in nearby areas, regardless of the distance to the road verge. However, this positive effect was restricted by increasing traffic intensity and narrower road verge width. Despite similar numbers of flower visitors at both distances, the pollination success, measured as the number of developed achenes on each harvested strawberry, tended to be lower closer to the road verge than further away but was unrelated to flower density, traffic intensity and road verge width, which indicates potential differences in pollinator behaviour or in the pollen they carried. Our findings highlight the potential of flower-rich road verges to support the conservation of flower-visiting insects. However, we emphasise the need to consider road verge width and traffic intensity to ensure successful pollinator-friendly management.