New Research: Trees Prove Vital to Human Health

Portland, OR (January 16, 2013) – Research published this month in the American Journal of Preventive Medicine suggests that tree loss from the spread of the emerald ash borer is associated with increased mortality related to cardiovascular and lower-respiratory-tract illness. The U.S. Forest Service study collected data in nearly 1,300 counties in 15 states over 18 years. These findings add to the growing evidence of the relationship between trees and human health, and the major public health benefits derived from the natural environment.

The longitudinal study quantifies the public health effects of the emerald ash borer, an invasive forest pest which has killed tens of millions of ash trees since it was first detected in the U.S. in 2002. The spread of the borer is a unique natural experiment allowing the evaluation of the effect of changes in the natural environment on public health.  In the study, the EAB is a proxy for tree loss.

Researchers analyzed demographic, human mortality, and forest health data at the county level between 1990 and 2007. Analysis was conducted between 2011 and 2012. The study sample includes 15 states that had at least one confirmed case of the borer in 2010. Data were observed annually at the county level (1296 counties), from 1990 through 2007.

Americans living in areas infested by the emerald ash borer, where tree-lined streets become treeless, suffered from an additional 15,000 deaths from cardiovascular disease and 6,000 more deaths from lower respiratory disease when compared to uninfected areas.

Results suggest that the widespread death of ash trees from the emerald ash borer lead to an increase in mortality related to cardiovascular and lower-respiratory-tract illness. These results are consistent with previous research that has identified a correlation between the natural environment and health.

According to the published research, the findings don’t provide direct insight into how trees might improve mortality rates related to cardiovascular and lower-respiratory-tract illness. The researchers do, however, outline several plausible mechanisms including trees improving air quality, reducing stress, increasing physical activity, moderating temperature, and buffering stressful life events.

Related Resources
The Relationship Between Trees and Human Health: Evidence from the Spread of the Emerald Ash Borer (Published Research)
Trees and Human Health May Be Linked (Science Daily)
When Trees Die People Die
Trees Linked With Human Health, Study Suggests