Mapping the diversity of street tree inventories across eight cities internationally using open data

Abstract

Tree diversity, on a species-, genus-, and family-level, is an important factor in securing healthy urban forests and providing ecosystem services for billions of city dwellers. Using open-source data on global tree inventories, this study examines (1) the diversity of species, genera, and family of urban street trees in eight cities internationally; (2) how they score on diversity benchmarks and indices; and (3) the diversity variation inside and outside of cities’ centers. We hypothesized most cities would score poorly on diversity benchmarks and spatial patterns in species composition would exist, as illustrated by established relationships between urban density and urban tree diversity. Results indicate city centers were less likely to approach the proposed diversity benchmarks than outside the city center. Overall, both Shannon and Simpson diversity indices show greater diversity outside of the city center, especially at the species-level. Understanding street tree diversity and spatial variation patterns across cities internationally can offer needed evidence to back up heuristic benchmarks. The methodology and open-source data used in this study are intended to enable practitioners better target tree diversity efforts.