Thursday, January 17, 2013

Is Tree Loss Linked to Mortality?

The unfortunate loss of 100 million ash trees to the emerald ash borer, an invasive pest from Asia, has provided a unique opportunity to deepen scientific understanding of the link between trees and public health.

After an analysis of 18 years of data from 1,296 counties in 15 states, the lead researcher, Dr. Geoffrey Donovan announced that “Americans living in areas infested by this insect suffered from an additional 15,000 deaths from cardiovascular disease and 6,000 more deaths from lower respiratory disease compared to uninfected areas.”

The pattern was consistent across variables such as race, income and education, but more research will be needed to determine the specific cause.

In fact, the mortality rates were highest in wealthier counties, probably because tree canopy often correlates with household income.

After being discovered in Detroit in 2002, the imported pest has swept through 22 species of North American ash virtually killing all of the trees it infests.

A researcher for the U.S. Forest Service, Donovan conducted the analysis in collaboration with scientists at the National Institute of Standards and Technology, Drexel University and other USFS research stations in various parts of the country.

The study is published in the February issue of The American Journal of Preventative Medicine.  While ash is not a large component of North Carolina forests overall, it is very popular in urban forests throughout the state, especially the component located on private property.

Trees have a proven economic value in providing scenic character and quality of place so essential to economic development.  They are also well documented sources of climate control, clean air and water, increased productivity, soil conservation, crime reduction, as well as better public health outcomes.

However, policy and lawmakers have seemed extremely slow to grasp the importance of forests.  In North Carolina, cities are replanting an average of only one tree for ever four that are removed and that is just counting the relatively small portion of urban forests located on city-owed property.

In Durham, NC where I live, officials are planting in an entire year what should be being planted each and every day to compensate for trees surrendered to impervious surface and development.

Ignoring overwhelming public opinion, state lawmakers recently gave out-of-state billboard companies permission to clear-cut $5 billion worth of publicly-owned trees along state roadways, ignoring tree ordinances in the cities and towns through which they pass.

Hopefully, it is only a matter of time before public policy will catch up with public opinion and the science documenting the incredible value of this component of green infrastructure.

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