Beyond Canopy Coverage: Species Composition, Urban Forest Equity, and Neighborhood Health in Chicago

Abstract

Urban canopy coverage has been linked with improved health outcomes, but most existing research is focused on canopy quantity rather than species composition. This study investigated whether canopy coverage predicts a composite health score across census tracts in Chicago, and aimed to motivate further research into the importance of urban tree species composition. IIT’s Alphawood Arboretum in Chicago was used as an empirical case study to lay the groundwork for future species specific analysis. CDC PLACES, ACS, and CRTI data were used to analyze health outcomes across 801 census tracts in Chicago. A composite health burden index was constructed using PCA, along with four progressive OLS regression models to predict the health burden index in different census tracts. Results indicated canopy coverage alone does not predict health burden (Model 1, p = 0.537), and the full model achieves $R^2$ = 0.887, which is driven by the poverty rate, educational attainment, and racial composition. The IIT Alphawood Arboretum allowed for an analysis of 1442 trees across 77 different species, with a Shannon Index of $H’ = 2.98$. The Thornless Honeylocust was the dominant species on campus, covering 32.0% of the campus, while also sequestering and storing the greatest amount of carbon. Priority planting tracts were also identified and were concentrated on Chicago’s South and West sides with Armour Square, South Chicago, and Fuller Park being the highest priority community areas. Neighborhood scale species composition data does not publicly exist for the city of Chicago and represents a genuine data infrastructure gap. The priority framework provides community organizations with evidence-based guidance on where to focus future investment. Future research should prioritize species-level documentation across Chicago’s urban forest to enable further testing of the species-health hypothesis.