Are the same factors determining biodiversity in cities across different regions? Comparing drivers of urban bird richness patterns in Southern Asia vs. Western Europe

Abstract

Abstract According to general urban ecological understanding, bird species richness declines in highly urban areas due to the increasing extent of built-up areas, and decreasing proportions of green areas. However, this hypothesis is mainly based on studies conducted in cities located in the Global North and rarely in the Global South. We aimed to assess whether existing conceptual understandings of drivers of bird species richness patterns within cities are similar across different regions, specifically Southern Asia (in the Global South) vs. Western Europe (in the Global North). Using avian occurrence data drawn from GBIF (gbif.org), we estimated resident bird species richness in 943 selected grid cells (each cell corresponding to approximately 1 km 2 area) distributed in 24 cities, 13 in Southern Asia and 11 in Western Europe. We applied generalised linear mixed models to relate resident bird richness with different explanatory variables of gradients of urbanisation, habitat and climatic factors using the selected grid cells as sampling units. Our results showed that bird richness declined with increasing human built-up and settlement extent (imperviousness) in both regions, but this relationship was stronger in Southern Asia compared to Western Europe. Bird richness also sharply declined in urban areas located far from inland waterbodies, but only in Southern Asia. Our findings suggest that high imperviousness drives bird richness decline, but this process appears to be more pronounced in regions where rapid urbanisation is ongoing. Urban planning integrating green spaces throughout cities is crucial in Southern Asia, as it is in Western Europe, to benefit both people and biodiversity.