In 2002, scientists discovered that a beetle known as the emerald ash borer was killing ash trees in the United States. By 2010, 100 million trees were dead. And so were at least 21,000 Americans who died along with the trees.
When the emerald ash borer comes into a community, city streets lined with ash trees become treeless. Researchers believe that the death of those trees also leads to extra human deaths. The comfort we derive from trees supports our health. Take that away and many of us can’t endure.
An analysis of 18 years of data from 1,296 counties in 15 States, showed that people living in areas infested by the 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.
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.
“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,” says 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.”