More than just green: the role of vegetation heterogeneity for species richness and multidiversity in urban green spaces

Abstract

<title>Abstract</title> Urban green spaces (UGS) provide ecological, social, and climatic functions, yet their effectiveness depends not only on area but also on vertical spatial structure. We present a high-resolution urban green space typology (UGST) for four Swiss cities (Basel, Bern, Geneva, and Zurich) derived from remotely sensed thematic (NDVI) and structural (vegetation height and complexity) data, comprising 33 classes. The structural heterogeneity of the vegetation cover was bimodal, with low-complexity vegetation <bold>(</bold> grass) or tall, high-complexity canopy (forest) dominating, while intermediate structures were underrepresented. The UGST was used to assess species richness across five taxonomic groups and a multidiversity score (mean normalized richness across all groups) using GAMs under varying thematic resolutions. Results showed that (1) species richness was shaped by the coverage and diversity of a broad variety of UGST classes, highlighting habitat heterogeneity as the primary driver over single vegetation types; (2) fine-grained UGST integrating thematic and 3D structure consistently outperformed aggregated classes and total green cover in explaining species richness and multidiversity.