Urban forest biodiversity and cardiovascular disease: Potential health benefits from California’s street trees

population data from the US Census and for 2011–2016 we used the annual estimated popula- tion from the Five Year American Community Survey (ACS). For 2017 and 2018, where we lacked population data, we used the 2016 ACS population estimate. Neighborhood characteris- tics were taken from Opportunity Insight’s “Neighborhood Characteristics by Census Tract” which is an assembly of data sourced from the 2010 Census, 2012–2016 American Community Survey, 2000 Decennial Census, and Longitudinal Employer-Household Dynamics (LEHD). Characteristics were aggregated from census-tract to ZCTA. Given Census ZCTAs are designed to coincide with census-tract boundaries we assume there is no mismatch error in aggregating the data up to the ZCTA geographic level. Zip code level pollution data from 2018 were taken from CalEnviroScreen (CES) 3.0 and merged across ZCTA. The only variable used within our analysis is CES 3.0’s Pollution Burden Index, which is an average across percentiles of pollution indicators such as PM 2.5 concentration, drinking water contamination, traffic density, groundwater threats, and prevalence of hazardous waste facilities. When merging these data with the mortality rates and forest characteristics, we lose zip codes because of miss- ing CES data and household income data from Opportunity Insights. The number of observa- tions falls to 4,959 (551 zip codes) for heart disease and 1,449 (161 zip codes) for stroke. Measures There are three key measures in our analysis: our outcome variable (mortality rate per 100,00

individuals), our control for exposure to trees (trees per 100,000 individuals), and our measure of biodiversity (Shannon-Weiner Index at the genus level). Like Donovan et al. [17], we express mortality from cardiovascular disease as a rate as opposed to a count. We transformed raw mortality counts into rates of mortality per 100,000 Fig 1. Variation in Urban tree diversity in California. Notes: Data for 857 zip codes in Heart Disease sample California from consortium of private tree maintenance companies. https://doi.org/10.1371/journal.pone.0254973.g001 PLOS ONE Biodiversity and cardiovascular disease PLOS ONE | https://doi.org/10.1371/journal.pone.0254973 November 3, 2021 6 / 23