Save a Tree and Save a Life: Estimating the Health Benefits of Urban Forests

Do trees in urban areas benefit human health? More than 100 million Americans live in large cities, yet little is known about the health benefits of the trees they live with. I provide causal evidence on the elasticity of air pollution and mortality to urban forest loss from the exogenous introduction of the emerald ash borer insect to the continental United States. Trees benefit urban health by reducing pollution; dieback that affects up to 5.8% of city forests is associated with increases in mean PM2.5 levels that reach 4.4%. Damage to city forests ultimately leads to excess deaths of up to 1.8%; much of this increase is driven by increases in cardiovascular and respiratory disease mortality. If the estimated median elasticity of all-cause mortality to tree damage of − 0.42 is extrapolated to all forests in the urban continental United States, my results imply urban forests reduced all-cause mortality by 29.3%, or 299,000 deaths total, in 2014.