Tree Species Diversity Enhances Urban Forest Resilience Globally

Urban forest resilience is essential for sustaining ecosystem functions in urban areas following extreme climate events. However, there remains a lack of scientifically informed strategies for effectively enhancing urban forest resilience. This study evaluated the influence of tree species diversity (Sd) on urban forest resilience in 388 cities worldwide, using the Global Urban Tree Inventory (GUTI) dataset and satellite-derived enhanced vegetation index (EVI) observations spanning 1986–2023. We found that cities situated in wet climates and characterized by lower levels of urbanization tended to exhibit higher Sd and greater forest resilience, whereas 86.3% of the 388 cities showed a declining trend in resilience over the study period. Correlation analysis demonstrated that increasing Sd was significantly associated with lower temporal autocorrelation (TAC), indicating higher resilience (r = −0.51, p < 0.01), and with a slower rate of resilience decline (r = −0.43, p < 0.01). These relationships were substantially stronger in arid and highly urbanized cities than in wet and less urbanized cities. We further employed a multivariate regression framework with interaction terms to test whether the species diversity effect (ρ) on urban forest resilience varied along gradients of climate and urbanization. The results confirmed a significant positive main effect of Sd on resilience, with 355 of 388 cities exhibiting positive ρ values. The interaction analysis revealed that this positive diversity effect was significantly amplified in drier cities and in those with higher urbanization intensity, indicating that species diversification yields the greatest resilience benefits in the most environmentally stressed urban settings. Our findings suggest that incorporating diverse tree species into urban ecological planning is essential for enhancing urban ecosystem resilience and promoting the development of green and sustainable cities, particularly in dry and highly urbanized regions.