Forest-attacking invasive species and infant health: evidence from the invasive emerald ash borer.
Trees provide many ecosystem services. Widespread tree loss, therefore, would lead to degradations in environmental quality, which might have spillover effects on human health. For the first time, the infant health externalities of tree loss caused by an invasive species are investigated. We exploit a quasi-experimental setting where millions of ash trees have been destroyed in the US due to the invasive emerald ash borer (EAB). Since EAB spread is quasi-random due to flight and weather, and since ash tree loss due to EAB is extensive, our research design can eliminate many environmental confounders of concern. We use rich, mother-level natality data covering the near-universe of US births over 1999-2015. Difference-in-differences results suggest that along the intensive margin, birth weight and gestation are lower by 12.19 g and 0.024 weeks, respectively, after EAB detection in the mother's county of residence. Along the extensive margin, the probability that a mother has a low birth weight baby increases by 0.2%, equivalent to an increase of 16.2 per 100,000 live annual births. Results are robust to using the synthetic control method and the Lasso method. An internal validity test shows that findings are not due to the changing composition of mothers after EAB.