When the emerald ash borer (a beetle) starts infesting and killing ash trees, the health of people in the area takes a nosedive, leading scientists to speculate that trees might play an important role in our wellbeing.
A new study from the U.S. Forest Service that links trees and health focused on regions affected by the emerald ash borer, a pest first discovered near Detroit in 2002. The borer attacks all 22 species of North American ash and kills virtually all of the trees it infests. Research forester Geoffrey Donovan, who authored the new study, said the beetle had so far caused the loss of 100 million trees in the eastern and midwestern United States.
In an analysis of 18 years of data from 1,296 counties in 15 states, Donovan found that Americans living in areas infested by the emerald ash borer suffered from an additional 15,000 deaths from cardiovascular disease and 6,000 more deaths from lower respiratory disease when compared to uninfected areas.
Although the study shows the association between loss of trees and human mortality from cardiovascular and lower respiratory disease, Donovan cautions that it does not prove a causal link.
Importantly, the findings hold true even after accounting for the influence of demographic differences, like income, race, and education. "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 Donovan. "But we saw the same pattern repeated over and over in counties with very different demographic makeups."
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Source: U.S. Forest Service