title: The relationship between trees and human health: evidence from the spread of the emerald ash borer.
abstract: BACKGROUND
  Several recent studies have identified a relationship between the natural environment and improved health outcomes. However, for practical reasons, most have been observational, cross-sectional studies.
  
  
  OBJECTIVE
  A natural experiment, which provides stronger evidence of causality, was used to test whether a major change to the natural environment-the loss of 100 million trees to the emerald ash borer, an invasive forest pest-has influenced mortality related to cardiovascular and lower-respiratory diseases.
  
  
  METHODS
  Two fixed-effects regression models were used to estimate the relationship between emerald ash borer presence and county-level mortality from 1990 to 2007 in 15 U.S. states, while controlling for a wide range of demographic covariates. Data were collected from 1990 to 2007, and the analyses were conducted in 2011 and 2012.
  
  
  RESULTS
  There was an increase in mortality related to cardiovascular and lower-respiratory-tract illness in counties infested with the emerald ash borer. The magnitude of this effect was greater as infestation progressed and in counties with above-average median household income. Across the 15 states in the study area, the borer was associated with an additional 6113 deaths related to illness of the lower respiratory system, and 15,080 cardiovascular-related deaths.
  
  
  CONCLUSIONS
  Results suggest that loss of trees to the emerald ash borer increased mortality related to cardiovascular and lower-respiratory-tract illness. This finding adds to the growing evidence that the natural environment provides major public health benefits.
authors: Pacific Northwest Research Station, U.S. Department of Agriculture Forest Service, Pacific Northwest Research Station, Portland, Oregon, USA. gdonovan@fs.fed.us
authors: Geoffrey H
authors: GH
authors: Donovan
authors: David T
authors: DT
authors: Butry
authors: Yvonne L
authors: YL
authors: Michael
authors: Jeffrey P
authors: JP
authors: Prestemon
authors: Andrew M
authors: AM
authors: Liebhold
authors: Demetrios
authors: D
authors: Gatziolis
authors: Megan Y
authors: MY
authors: Mao
mesh_terms: D000818:Animals; D002318:Cardiovascular Diseases / Q000453:epidemiology* / Q000401:mortality; D001517:Coleoptera; D004777:Environment; D031661:Fraxinus; D006801:Humans; D008137:Longitudinal Studies; D017063:Outcome Assessment, Health Care; D011634:Public Health; D012044:Regression Analysis; D012140:Respiratory Tract Diseases / Q000453:epidemiology* / Q000401:mortality; D012959:Socioeconomic Factors; D014197:Trees; D014481:United States / Q000453:epidemiology