Newer studies are supporting the hypothesis that exposure to the natural environment can improve human health. In a new study by the U.S. Forest Service published recently in the American Journal of Preventive Medicine, the presence of trees was seen to promote human health.
100 million trees were lost in the eastern and midwestern United States. This provided an unprecedented opportunity to Geoffrey Donovan, a research forester at the Forest Service’s Pacific Northwest Research Station, and his colleagues to study the impact of a major change in the natural environment on human health.
They analysed 18 years of data from 1,296 counties in 15 states, and 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. Emerald ash borer eats into trees lining the street and ash trees become lifeless.
“ 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.”
Although the study shows the relationship between loss of trees and human mortality from cardiovascular and lower respiratory disease, it did not prove one causes the other. The reason has yet to be established.