A systematic review and meta-analysis on urban arthropod diversity

Urbanization is rapidly expanding at the global level, a phenomenon often reported to exert negative effects on biodiversity. However, many important knowledge gaps about the effect of urbanization on biodiversity remain, posing important conservation challenges. This is especially true for certain taxonomic groups like arthropods, despite being the most diverse and abundant animal group on Earth. Here, we conduct an exhaustive systematic literature review and meta-analysis to assess whether and how urbanization is negatively associated with arthropod diversity. We explored potential geographic, temporal and taxonomic biases in the availability of evidence. In addition, we make use of meta-analysis of variance to investigate whether urban areas across the world show similar patterns of arthropod diversity change. Our results support previous studies; urbanization and arthropod diversity are negatively associated. However, not all arthropod groups seem to respond similarly (e.g., Odonata) potentially suggesting the importance of implementing taxa-specific conservation actions in urban areas. On the other hand, our meta-analysis of variance showed higher variance in arthropod diversity in urban compared to non-urban habitats, suggesting great potential for the implementation of certain city conservation practices or attributes to promote arthropod communities. Last, we identified several key taxonomic and geographic biases that require additional scientific attention as well as strong evidence for negative-effects publication bias in the literature. Our results highlight the importance of urban ecology research for helping design more diverse urban ecosystems.