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

RESEARCH ARTICLE Urban forest biodiversity and cardiovascular disease: Potential health benefits from California’s street trees John J. GiacintoID1☯, G. Andrew FrickerID2‡, Matthew Ritter3‡, Jenn Yost3‡, Jacqueline DoremusID1☯* 1 Economics, California Polytechnic State University, San Luis Obispo, CA, United States of America, 2 Social Sciences, California Polytechnic State University, San Luis Obispo, CA, United States of America, 3 Biological Sciences, California Polytechnic State University, San Luis Obispo, CA, United States of America ☯ These authors contributed equally to this work. ‡ These authors also contributed equally to this work. * jdoremus@calpoly.edu Abstract Enhanced immune functioning in response to biodiversity may explain potential health ben- efits from exposure to green space. Using unique data on urban forest biodiversity at the zip code level for California measured from 2014 to 2019 we test whether greater diversity of street trees is associated with reduced death from cardiovascular disease. We find that urban forests with greater biodiversity measured via the Shannon Index at the genus level are associated with a lower mortality rate for heart disease and stroke. Our estimates imply that increasing the Shannon Index by one standard deviation (0.64) is associated with a decrease in the mortality rate of 21.4 per 100,000 individuals for heart disease or 13% and 7.7 per 100,000 individuals for stroke or 16%. Our estimates remain robust across several sensitivity checks. A policy simulation for tree planting in Los Angeles based on our esti-

mates suggests that if these relationships were causal, investment in planting for a more biodiverse set of street trees would be a cost-effective way to reduce mortality related to car- diovascular disease in urban areas. Introduction Cardiovascular diseases, including heart disease, stroke, and hypertensive disease, are among the most preventable causes of death in the U.S. and worldwide [1–3] and cost the U.S. $199 billion in health care costs and $131 billion in lost job productivity annually [4]. Prescription drug treatment of cardiovascular disease has improved, shifting the policy focus to prevention [3]. Cost-effective ways to prevent cardiovascular may be situated outside traditional health care systems. Though they have existed in principle since at least the 19th century, “green pre- scriptions,” or nature-based health interventions, are garnering attention and may help pre- vent cardiovascular disease [5]. For example, a short walk through a forest lowers blood pressure [6] and living in greener areas is associated with a reduced risk of cardiovascular dis- eases [7]. PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0254973 November 3, 2021 1 / 23 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Giacinto JJ, Fricker GA, Ritter M, Yost J, Doremus J (2021) Urban forest biodiversity and cardiovascular disease: Potential health benefits from California’s street trees. PLoS ONE 16(11): e0254973. https://doi.org/10.1371/journal. pone.0254973 Editor: Ghaffar Ali, Shenzhen University, CHINA Received: July 29, 2020

Accepted: July 8, 2021 Published: November 3, 2021 Copyright: © 2021 Giacinto et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by Cal Fire California Urban Forest Inventory Award # 8GA19405 (MR) https://www.fire.ca.gov/ The funders did not play any role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: No authors have competing interests.