Do Dying Trees Lead to More Human Deaths? The Debate Continues

The relationship between trees and human health: evidence from the spread of the emerald ash borer.

Donovan GH, Butry DT, Michael YL, Prestemon JP, Liebhold AM, Gatziolis D, Mao MY.

Source

Pacific Northwest Research Station, U.S. Department of Agriculture Forest Service, Pacific Northwest Research Station, Portland, Oregon, USA. gdonovan@fs.fed.us

Abstract

BACKGROUND:

Several recent studies have identified a relationship between the natural environment and improved health outcomes. However, for practical reasons, most have been observational, cross-sectional studies.

PURPOSE:

A natural experiment, which provides stronger evidence of causality, was used to test whether a major change to the natural environment-the loss of 100 million trees to the emerald ash borer, an invasive forest pest-has influenced mortality related to cardiovascular and lower-respiratory diseases.

METHODS:

Two fixed-effects regression models were used to estimate the relationship between emerald ash borer presence and county-level mortality from 1990 to 2007 in 15 U.S. states, while controlling for a wide range of demographic covariates. Data were collected from 1990 to 2007, and the analyses were conducted in 2011 and 2012.

RESULTS:

There was an increase in mortality related to cardiovascular and lower-respiratory-tract illness in counties infested with the emerald ash borer. The magnitude of this effect was greater as infestation progressed and in counties with above-average median household income. Across the 15 states in the study area, the borer was associated with an additional 6113 deaths related to illness of the lower respiratory system, and 15,080 cardiovascular-related deaths.

CONCLUSIONS:

Results suggest that loss of trees to the emerald ash borer increased mortality related to cardiovascular and lower-respiratory-tract illness. This finding adds to the growing evidence that the natural environment provides major public health benefits.

Published by Elsevier Inc.

Comment in

• The evidence of nature and the nature of evidence. [Am J Prev Med. 2013]

PMID:

 

23332329

 

[PubMed - in process]

Do Dying Trees Lead to More Human Deaths? The Debate Continues

The hypothesis: Trees improve people's health.

The experiment: Remove 100 million trees in the eastern and midwestern United States over the course of 10 years and see what happens.

What happened: People died.

In the 15 states infected with the emerald ash borer -- which killed all 100 million of those trees -- an additional 15,000 people died from cardiovascular disease and 6,000 more from lower respiratory disease compared with uninfected areas of the country.

After studying data from 1,296 counties and accounting for other variables, research forester Geoffrey Donovan and his team at the U.S. Forest Service concluded that having fewer trees around may be bad for your health. Their study -- published recently in the American Journal of Preventive Medicine -- concluded that there's an associative link between trees health and human health. Proving a direct, causal link will take much more research.

When the PBS NewsHour published a discussion with Donovan earlier this week, many viewers remained quite skeptical. One wrote that "this hypothesis has no more scientific validity than a theory that the darkness of night causes mice to spontaneously generate." The questions multiplied when the story was posted on reddit and Slashdot.

Joining us once again to answer a representative set of those questions is Geoffrey Donovan.

go to this link to read the Qs & As   http://www.pbs.org/newshour/rundown/2013/06/how-closely-can-tree-health-be-tied-to-human-health-debate-continues.html