Metabarcoding assessment of arthropod diversity on green roofs in the metropolitan city of Hamburg

Cities have become valuable alternative habitats for many organisms, particularly arthropods, as they often offer more favourable environmental conditions, and greater resource availability compared to neighbouring intensive agroecosystems. However, urban biodiversity is threatened by habitat loss and fragmentation, driven mainly by urban development and densification. Green roofs are novel urban green spaces that may represent valuable stepping stones, supporting various taxa. However, so far, only few studies have evaluated the potential of green roofs to support the conservation of biodiversity in cities. Here, we assessed species richness and diversity of vascular plants and arthropods on eight extensive green roofs in the city of Hamburg in northern Germany to understand which local green roof parameters and landscape scale factors may support high arthropod richness on green roofs. Plant diversity varied between roofs, but none of the parameters explained the variance in plant diversity, with only age having a slightly negative effect. Arthropod richness was positively influenced by green roof size and arthropod composition by diversity of vascular plants on the green roofs. In addition, the amount of green land use types surrounding the location of the green roof had a positive effect on arthropod richness. Our results indicate that green roofs can harbor various arthropod species and could function as urban stepping stones for many species to enhance the connectivity of existing green spaces and, thereby, enhance urban biodiversity. The Author(s) 2025.