Corey Thomas Callaghan, Gracie Liu, Brittany A. Mitchell, Alistair G. B. Poore, Jodi Rowley

Urban environments are novel ecosystems, with increased chemical, sound, and light pollution differentially impacting many animals. Understanding the impacts of urban environments on biodiversity is the first step to understanding how to best mitigate biodiversity losses in an increasingly urbanizing world. Analyses with broad geographic and taxonomic coverage can offer critical context for informing urban biodiversity conservation. But such studies are currently lacking, especially for under-studied but likely highly impacted taxa such as frogs. Our objective was to document frog diversity in relation to urban environments at continental, regional, and local scales. We used FrogID data ⁠— an opportunistic citizen science dataset generated by volunteers recording calling frogs using a smartphone and validated by experts ⁠— throughout continental Australia, to calculate species richness, Shannon diversity, and phylogenetic diversity of frogs in urban and non-urban areas, as well as along a continuous urbanization gradient. The overall species richness of frogs was, on average, 57% less in urban than non-urban areas across six ecoregions. Further, we found significantly lower frog diversity in urban environments compared with non-urban environments across the country, with an average reduction of 59% species richness, 86% Shannon diversity, and 72% phylogenetic diversity. We also found evidence for a steady decrease in frog diversity along an urbanization gradient, with no obvious thresholds. Our results highlight the negative impacts of urbanization ⁠— at a continental scale ⁠— on frog diversity, and clearly highlight the necessity to consider frog diversity in future urban land development decisions.