Building dense or compact cities without jeopardizing biodiversity: Insights from bird observations in Gothenburg, Sweden.

A central challenge for sustainable urban development is balancing the trade-offs of high urban density. We examined whether biodiversity can be supported within dense or compact urban areas by analyzing bird species richness and composition across 30 sites in Gothenburg, Sweden, representing three urban form types (two compact and one dense) and reference areas with abundant vegetation. Results showed that species richness was significantly lower in the three urban form types than in the reference areas, and species composition differed significantly between the two groups. However, there were no significant differences in species richness or composition between the individual urban form types themselves. Across the three urban form types, nevertheless, sites with larger local natural habitat area and/or better connectivity to surrounding natural habitats had higher species richness, whereas variation in species composition was associated primarily with local habitat area. This highlights that increasing habitat area remains the most effective strategy for supporting avian diversity, even in dense or compact urban areas. Species that are less common in urban areas were also recorded at sites within the three urban form types where suitable conditions existed. These results not only suggest that biodiversity can exist within dense or compact urban areas but also that it can be supported through both site-level interventions and broader-scale planning for habitat connectivity.