Living Without Trees Causes Higher Mortality Rates

An interesting link was found between the absence of trees in the (urban) environment where humans live, and significantly increased cases of death from heart disease and respiratory illness. Researchers at the Forest Service's Pacific Northwest Research Station did a lot of data-mining in health statistics, spanning a period of 18 years, and ran statistical estimates selecting for deviations depending on the abundance, or absence, of trees.

The United States experienced a loss of 100 million trees in the eastern and mid-western parts, providing a good opportunity to study the impact of a major change in the natural environment on human health. The result of the estimates were that in areas with few trees, for example due to infestation by insects that kill trees, 15,000 more deaths from cardiovascular diseases and 6,000 more from respiratory illness occured, compared to the areas with a higher number of trees.

Geoffrey Donovan, a research forester at the Forest Service's Pacific Northwest Research Station, is conducting urban forestry research, an already estimated the impact of trees on house prices, rental prices, crime, energy use, and birth outcomes. He says that the study accounted for other factors than trees, and finds a clear link to health: "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 in a report published by Science Daily. "But we saw the same pattern repeated over and over in counties with very different demographic makeups."

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.