1. Current inequality and future potential of US urban tree canopy cover for reducing heat-related mortality, morbidity and electricity consumption
- Author
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Robert McDonald, Tanushree Biswas, Tirthankar Chakraborty, Timm Kroeger, Susan Cook-Patton, and Joseph Fargione
- Abstract
Excessive heat is a major and growing risk for urban residents. Urban trees can significantly reduce summer peak temperatures, thus reducing heat-related mortality, morbidity, as well as cooling energy demand. However, urban tree canopy is inequitably distributed in US cities, which has been shown to contribute to higher summer temperatures in people-of-color (POC) neighborhoods. Here, we utilize a unique dataset of high-resolution tree canopy cover to estimate the inequality in summertime heat-related mortality, morbidity, and electricity consumption across a sample of 5,723 US municipalities and other places, housing 180 million people during the 2020 census (50.6% in majority non-Hispanic white neighborhoods, 49.4% in majority people-of-color, POC, neighborhoods). We also model the potential to increase tree cover in these municipalities in 5% increments up to a realistic maximum, the 90th percentile of tree cover observed in each municipality for each impervious surface class. On average, trees in non-Hispanic white neighborhoods cool the air by 0.19 ± 0.05⁰C more than in POC neighborhoods, leading annually to trees in white neighborhoods helping prevent 190 ± 139 more deaths, 30,131 ± 10,406 more doctors’ visits, and 1.4 ± 0.5 terawatt-hours (TWhr) more electricity consumption than in POC neighborhoods. The greatest inequality in the protective value of trees occurs in the Northeastern US. We estimate that for these 5,723 municipalities, the maximal feasible urban reforestation program in residential neighborhoods could add 1.2 billion trees, reducing population-weighted average summer temperatures by an additional 0.38 ± 0.01⁰C. Relative to the current status quo, this increase in the cooling benefits of trees would reduce annual heat-related mortality by an additional 464 ± 89 people, annual heat-related morbidity by 80,785 ± 6110 cases, and annual electricity consumption by 4.3 ± 0.2 TWhr, while increasing annual carbon sequestration in trees by 23.7 ± 1.2 MtCO2e and decreasing annual electricity-related GHG emissions by 2.1 ± 0.2 MtCO2e. The total economic value of these benefits, including the value of carbon sequestration and avoided emissions, would be USD 9.6 ± 0.5 billion, although in many neighborhoods the cost of increased tree cover exceeds these benefits. The exception is neighborhoods that currently have lower tree cover, especially those that are majority POC, as these neighborhoods have a much higher return-on-investment from tree planting.
- Published
- 2023
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