COMMENT FROM A U.S.
FOREST SERVICE ENTOMOLOGIST ON THE MAPPING OF WIDESPREAD FOREST
DEATH IN PENNSYLVANIA
Sent: Tuesday, August 28, 2001 12:41 PM
Subject: Health and Science
The article that you ran yesterday,
"Survey project maps tree death along Appalachian
ridges" was full of errors that presented a very misleading
impression to your readers. There is actually very little
evidence of effects of air pollution in eastern forests. In
contrast, the impacts of exotic insects and pathogens has been
devestating. Two of your examples
(Allegheny Nat. Forest and Mt. Mitchell, NC) are actually examples of massive tree death caused by exotic
species, not air pollution. To imply that these problems are caused by air pollution only serves to focus public attention away from the REAL problem threatening the health of our forests - an epidemic of foreign pests as a result of increased global trade. You really should have researched this story more carefully because virtually any legitimate scientists (at a major university) could explain this problem to you. I am a research entomologist with the US Forest Service in Morgantown, WV and would be glad to help you get the word out about the threat to our forests that alien species cause.
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REPLY TO U.S. FOREST SERVICE ENTOMOLOGIST
From: Harvard <email@example.com>
Subject: Allegheny NF Forest Decline article
Andrew Liebhold- My name is Harvard Ayers, Anthropology and Sustainable Development, Appalachian State University. I recently flew with my cartographer colleague Ron Hancock over the declining sugar maple/beech forest of the Allegheny National Forest. I am responding to your email to Don Hopey (Pittsburgh Post Gazette) who flew with us over the ANF on
Monday the 20th.
I think you might want to consider a
broader view of forest decline in the eastern US. While exotic
bugs and disease have had a substantial impact on our native
forests, many of the problems in the forest today are the result
of a combination of factors and the proximal cause of death
of the species like the sugar maple and the beech are in most
cases pathogens and pests that are as native as the trees
themselves. And some of the exotics like the dogwood anthracnose
and the balsam wooly adelgid have killed the trees while
interacting with other stress factors such as weather and air
pollution. I can get you specific references for these ideas, but
I especially refer you to works by one of your colleagues, Bob
Anderson (now in Atlanta with the USFS), that clearly document
the important weakening effect played by air pollution in the
demise of the
The science behind the general concept of air pollution as a weakener and stressor is well-established. As soils go below about 5.0 pH, and especially when they go below 4.0, a basic ecological change of the greatest possible significance to the forest ecosystem occurs. If we consider that the soils (along with air and water) are the basis of the forests, when critical nutrients such as calcium and magnesium are reduced, we may have a shortage of nutrients available to the trees. Combine this with the release of toxic aluminum from the aluminum silicates present in essentially all soils and you have a greater problem. The Al gets into the vascular structure of the plant and inhibits nutrient uptake. The third chemical change that occurs in acidified soils is reduction in the resistance of the tree to fight off pests and disease.This comes about largely when the tree absorbs (mostly through its roots) large quantities of nitrogen, mainly that from air pollution. The high-carbon secondary metabolites are depressed as the C:N ratio falls thus making the trees further susceptible to pest and disease.
Another negative soil effect concerns the health of the insects and other forest litter processors. Earthworms, for instance, are reduced in numbers as acidity increases to about pH 4.0, when they drop out all together.Many other soil organisms are reduced or eliminated by this point. These organisms function to process the litter, making its nutrients more accessible to the trees.
The biggest threat to the foliage is ozone. It functions to actually kill cells in the leaves, thus reducing the photosynthetic efficiency of the tree. In most cases, this can be sustained for a number of years, as the tree can live off its reserves for perhaps a decade or even more. But again, the overall health of the tree is significantly compromised. In combination with the soil insults described above, the tree can become ripe for the harvest by bugs or disease, either exotic or indigenous.
Concerning the maple/beech problems in the Allegheny National Forest, it would appear that we have a classic case of acidified soils which have reduced nutrients and released toxic aluminum to the point that pests and disease are taking their toll. We found what I identified as beech scale on the dying beech trees in the Tionesta Scenic/Natural area. The best documentation of the negative soil effects in the area has been done by Bill Sharpe of Pennsylvania State University.
Dr. Sharpe's ideas, while controversial in circles that are skeptical of air pollution's effects on forests, have been strongly supported in a recent peer-reviewed article in March, 2001, Bioscience. The group of a dozen or so authors, all scientists associated in one way or another with the research at the USFS research forest at Hubbord Brook, which includes Gene Likens, came to the conclusion that the sugar maple problems in Pennsyvania are due to acid precipitation-induced soil problems much as Dr. Sharpe described.
I would suggest that you perhaps talk with a number of well-respected researchers who are at large universities and government posts across our country. Drs. Bob Bruck (NC State University), Orie Loucks (Miami University), Bill Sharpe (Penn State University), Bill Grant (NASA) Steve McNulty (USFS, Raleigh), and Gene Likens (Hubbard Brook and other associations) could fill Mr. Hopey in on the interactive nature of the stressors on our eastern forests.
In terms of references, I would recommend that you might want to look at a book I co-edited, "An Appalachian Tragedy, Air Pollution and Tree Death in the Eastern Forests of North America." It has an excellent bibliography of well-established researchers' work in the US and other countries that fully accept the significant role that air pollution has played in forest decline around the world, including the East. My book contains several essays written by well-known authors ranging from social science to biological science to political science. One of my co-editors, Charles Little, has written another instructive book, "The Dying of the Trees," which I would recommend as well.
Dr. Liebhold, I would suggest that your cavalier dismissal of the other side of this significant scientific controversy of air pollution's effects on forests is not a helpful approach. I understand that entomology is your specialty, and that you are very knowledgeable about the subject. But it seems to me that we need to pull the knowledge of different specialists together to gain a better understanding of the serious forest health problems that exist across the eastern US.
Thanks for your time. Harvard Ayers
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