Thoughts on the Causes of Tree Mortality in Appalachia

Abstract

In an article on the history of atmospheric sciences by Paul Crutzen and Veerabhadran Ramanathan (Pathways of Discovery, “The ascent of atmospheric sciences,” 13 Oct., p. [299][1]), there is a picture of dead trees in the Great Smoky Mountain National Park (p. 301). The caption indicates that these are red spruce ( Picea rubra ) that have died from acid rain fallout. First, the trees pictured are most likely Fraser fir ( Abies balsamea ) and, if so, they died from an introduced insect, the balsam woolly adelgid ( Adelges tsugae ), not from air pollution. Second, mortality rates for red spruce in the southern Appalachians are not elevated above what are considered to be normal background levels. And finally, there is no scientific evidence that the pictured trees—or, for that matter, trees anywhere in the eastern United States—have died from either acid rain or ozone pollution. This statement should not be construed to mean that air pollution is not a problem. Rather, it simply emphasizes that air pollution in the eastern United States has not yet reached levels that allow researchers to make a direct link to tree mortality. [1]: /lookup/doi/10.1126/science.290.5490.299