Vertical life: impact of roof height on beetle diversity and abundance on wildflower green roofs

Despite their increasing popularity in an urban setting, we still know relatively little in how well-extensive green roofs support biodiversity in terms of vertical connectivity from terrestrial habitats. Most green roof biodiversity studies have not considered whether the roof height affects community composition and abundance of species present. This study focused on evaluating beetle diversity and abundance in relation to roof height, with emphasis on wildflower roofs. The key results of the study confirm previous studies found that extensive wildflower green roofs are capable of supporting fairly rich beetle communities, including some rare/scarce species. However, an increase of roof height was found to negatively impact both beetle abundance and richness, despite all recorded species being well adapted to active flight and thus dispersal. In addition forb cover decreased with roof height which consequently influenced beetle community structure. These results are therefore indicative that further research is required on species communities found on extensive green roofs that are less adapted to active flight and consequently vertical dispersal. This study further highlights the need for vertical and horizontal connectivity between green roofs and the surrounding natural habitats as a management tool to increase the general ecological value of urban green spaces.