Urbanisation and landscape configuration influence biodiversity, yet multi-taxonomic studies that capture the complexity of urban landscapes remain scarce. Therefore, we conducted a multi-taxonomic hierarchical urban habitat analysis based on opportunistic citizen science data (n = 117,872 records) for Salzburg City and its surroundings. We investigated species richness for nine taxonomic groups on the level of landscape types, which were calculated for 500 m hexagonal grid cells using a hierarchical cluster analysis. Suburban areas show the highest absolute species richness for most taxa, except for insects. Analysing average species richness revealed that suburban habitats harbour high biodiversity but highest average species richness for most organism groups was found at water bodies and neighbouring riparian areas. Plant species richness also peaked in highly urbanised areas, yet mostly due to non-native species. The average richness for birds and mammals is high in urbanised areas as well. Grasshoppers and reptiles show high species richness in both rural and (sub-)urban areas. In contrast, butterflies, dragonflies and amphibians are species-poorer in urbanised areas. Intensively utilised agricultural areas had a very low average richness across all taxonomic groups. In summary, highly urbanised areas seem to be species-poor, especially for insects and amphibians, but species-rich for other groups. We conclude that the presence of water bodies, riparian areas and structurally rich suburban areas play a key role in supporting high biodiversity. Moreover, agriculture should be given greater consideration in future studies on urban biodiversity. The study addresses the need for multi-taxonomic studies in urban biodiversity research and demonstrates that opportunistic citizen science data are a valuable source for analysing biodiversity.
Schubert et al. (Fri,) studied this question.