A tree-lined street in Toledo, Ohio in 2006, before emerald ash borer infestation. Photo courtesy Dan Herms, Ohio State University.
Forest Service research links the presence of trees with human health
By Summit Voice
FRISCO — There’s a good reason that environmentalists have been called treehuggers from time to time — instinctively, some of us know how vital forests are to the health of the planet.
Now, some empirical research shows that’s true not just metaphorically, but that the loss of trees in the environment can have serious consequences for human health. The study by the U.S. Forest Service looked at the loss of more than 100 million ash trees in the East and Midwest.
Three years later, in 2009, after the invasive insect spread to the neighborhood. Photo courtesy Dan Herms, Ohio State University.
After analyzing 18 years worth of data from 1,296 counties in 15 states, researchers found that Americans living in areas infested by the emerald ash borer, a beetle that kills ash trees, suffered from an additional 15,000 deaths from cardiovascular disease and 6,000 more deaths from lower respiratory disease when compared to uninfected areas. When emerald ash borer comes into a community, city streets lined with ash trees become treeless.
“ 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,” said Geoffrey Donovan, a research forester at the Forest Service’s Pacific Northwest Research Station. “But we saw the same pattern repeated over and over in counties with very different demographic makeups.”
The researchers analyzed demographic, human mortality, and forest health data at the county level between 1990 and 2007. The data came from counties in states with at least one confirmed case of the emerald ash borer in 2010. The findings — which hold true after accounting for the influence of demographic differences, like income, race, and education—are published in the current issue of the American Journal of Preventive Medicine.
Although the study shows the association between loss of trees and human mortality from cardiovascular and lower respiratory disease, it did not prove a causal link. The reason for the association is yet to be determined.
The emerald ash borer was first discovered near Detroit, Michigan, in 2002. The borer attacks all 22 species of North American ash and kills virtually all of the trees it infests.
The study was conducted in collaboration with David Butry, with the National Institute of Standards and Technology; Yvonne Michael, with Drexel University; and Jeffrey Prestemon, Andrew Liebhold, Demetrios Gatziolis, and Megan Mao, with the Forest Service’s Southern, Northern, and Pacific Northwest Research Stations.
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