January 29th, 2013 by

By Michelle Werts

In the Winter 2013 issue of American Forests, American Forests Science Advisory Board member Dr. Deborah McCullough reveals how tens of millions of ash trees have been lost since 2002 due to the invasive insect, emerald ash borer. In new research released earlier this month, scientists report that the loss of those ash trees may be affecting more than just the health of rural and urban forests — their loss may be affecting human health.

Dead ash trees in Ann Arbor, Mich.

Dead ash trees in Ann Arbor, Mich. Credit: Steven Katovich, U.S. Forest Service, Bugwood.org

In the February 2013 issue of American Journal of Preventive Medicine, a team of U.S. Forest Service researchers led by Dr. Geoffrey Donovan published a study showing an association between tree loss and increases in deaths related to cardiovascular disease and lower respiratory disease. Dr. Donovan and his team used the “natural” deaths of 100 million ash trees to see if a major change in the natural environment had a correlation to mortality.

Studying data from 1,296 counties across 15 states affected by emerald ash borer-caused tree loss over a span of 17 years (1990-2007), the researchers discovered an additional 15,080 deaths from cardiovascular disease and 6,113 additional deaths from lower respiratory disease in counties infested with emerald ash borer after accounting for the influence of factors like income, race and education.

Dr. Donovan told Science Daily, “There’s a natural tendency to see our findings and conclude that, surely, the higher mortality rates are because of some confounding variable, like income or education, and not the loss of trees, but we saw the same pattern repeated over and over in counties with very different demographic makeups.”

The researchers are quick to point out, though, that while their study shows a correlation between human mortality and tree loss, it’s not a direct causal relationship. However, it is clear that there is a connection of some kind between loss of trees and a decline in human health. So remember that those trees you see around aren’t just helping four-legged critters stay safe, healthy and happy, they’re helping us, too.