LETTERS
Airborne chemicals
transporting or housing such a tree in Dear Sir: In response to the article, the lab? This predicament has led researchers “Airborne chemicals and forest health” (ES&T, February 1987, pp.120-26), I in Germany to attempt to take the lab to would like to offer a European view- the forest rather than the other way point. around, as is suggested by the authors. Ellis Cowling is among the few sci- While we give up some aspects of conentists who have a very in-depth knowl- trolled conditions, we gain insight into edge of the interaction of air pollutants some relevant conditions affecting tree and forests and their observable expres- health (e.g., continued leaching of nusion in the forests of Eastern North trients from the canopy and the soil occurring at the same time as abnormally America and Europe. His most recent article about this frequent flower allows us to observe topic, coauthored by Jim Woodman, cone and seed production). When such warrants a critical response from a Eu- phenomena are correlated to outside inropean viewpoint. I will try to focus on fluences, we can then attempt to test two aspects: corrections of factually in- specific physiological functions in the correct statements, and-what may be lab. While the eight sources that the aumore important-the role of the scientist facing increasingly complex and un- thors cite support their claim that “most certain phenomena in determining European and North American studies of the detrimental effects of air polluguidelines for research policy. While there is no disagreement that tants on forests have been made near we do not know all the facts about the metal smelters and other major sources forest dieback issue, we are also learn- of SO2, NO,, and F- or Fz,” only one ing through our research that it is very of the original research papers was pubunlikely that we will ever unravel the lished after 1980. On the other hand, complete details of the forest dieback the realization that we are dealing with phenomenon. This insight is based on a regional and continental problem, and the fact that it is impossible to test the not with local effects, only became interaction of the more than 2000 possi- widely known around 1980. It is little ble chemical agents of man-made ori- wonder that the sources cited do not gin that might in some way play a role address this issue. We have in Europe in the forests today and at the same time an array of articles dealing with just determine their interaction with each that aspect (1-12). This also means that the statement other and other compartments of the forest ecosystem like the biotic and “Very few reliable air quality measurements have been made in injured forchemical constituents of the soil. I would agree that the use of Rule 2 ests’’ is incorrect. As part of the counof Koch’s postulates is a noble goal. But trywide damage assessment it was its rigid definition will rule out the ex- necessary to establish deposition meaamination of some of the very factors suring stations. From the collected data we are trying to test. The application of we now know what amounts of polluKoch’s Rule 2 requiring controlled con- tants are filtered out by coniferous or ditions will, in my opinion, hinder the deciduous trees. We also have to disscientific progress. We find damage cuss the term “air quality” in this consymptoms predominantly in trees 60 text: Are the authors referring to conyears and older (as stated by the au- centrations of gases, or does air quality thors), but we can only use very young include levels of dry and wet deposition trees in the laboratory (possibly up to that have turned out to be the more relage 10-12). How can we simulate the evant criteria? If the latter is the case, accumulation of effects an older tree we can again supply the authors with a has been subjected to during its life- long list of articles showing that depositime, let alone the impossibility of tion levels within the forest stands can 612 Environ. Sci. Technol., Vol. 21,
No. 7, 1987
approach levels as severe as those in the air quality control region of our industrial centers. Are the damaged trees “distributed at random in forest stands”? Certainly not. We have good evidence from a study using a 4-km grid pattern over the whole southwestern corner of West Germany (specifically, the area comprised by the state of Baden-Wurttemberg), which shows us that the likelihood of a tree being damaged depends largely on its social status within the stand, that is, the exposure of its crown to the surrounding air. ’Rees growing in naturally mixed stands (beech, spruce fir) suffer more than trees growing in even-aged, single-species stands where the canopy tends to form a smoother surface. Shouldn’t we follow up the evidence that trees that grew better than average for most of their past 60 years are now suffering more because their canopies are exposed more to the elements? Are there really no studies showing losses in forest productivity? From a European perspective we have to disagree. Especially for silver fir but also for Norway spruce, we have studies showing good correlation of growth decline and tree damage going in some cases as far back as the late 1950s. These have been done with careful attention to the other parameters influencing tree growth. Should we really disregard all these pieces of evidence and many more that were not alluded to here, or shouldn’t we continue to test these findings? Airborne chemicals always act in combination with natural stresses. As natural stresses have not changed to the degree that airborne chemicals have, aren’t we forced to take a serious look at them? Let me address the question of what the outlook is for the research path in this field and therefore for the forests in Europe. According to 1986 statistics, there are now more than 35 million acres of forests in Europe damaged to some degree by the “novel forest dieback,” as the governments like to call it. That fig-
0013-936)(187/0921-0612$01.50/0 0 1987 American Chemical Society
ure would be cause for grave concern even if it were many times smaller than it is. Society has to deal with this unclear but very present danger. It is the duty of the scientist to unearth the causes for this demise. This phenomenon cannot be explained with scientific certainty of 95 % . Nevertheless, in facing this threat we have to develop a policy that relies on a lower level of certainty. The scientist then has to support his findings, even if the certainty is less than what was considered normal. It is therefore not surprising that the government of West Germany has passed legislation that will effect a reduction of SO2 and NO, emissions by 60% and 30%, respectively, over the next six years, while knowing full well that 100%scientijc certainty for such an action does not currently exist. But after weighing the risks of inaction, the government decided to legislate a program that will cost $5 billion. German legislators used the same logic that guided the D.C. circuit court judge presiding over the case Ethyl C o p vs. EPA, who stated: “Questions involving the environment are particularly prone to uncertainty...Yet the statutes and common sense demand regulatory action to prevent harm, even if the regulator is less than certain that harm is otherwise inevitable.” The judge elaborated on this point: “Even scientific ‘facts’ are not certain but only theories with high probabilities of validity. Scientists typically speak not of certainty, but of probability; they are trained to act on probabilities that statistically constitute ‘certainties’.” But where is the policy maker to get a balanced presentation of the findings to decide an issue if it does not come from the scientist most familiar with the issue? The article falls short of examining with the same diligence the probability that airborne chemicals are to blame that was employed in arguing a case for natural causes. I read this article in its entirety in the Minneapolis airport, where I was stranded for two hours because of a malfunctioning landing gear light on the aircraft that was to take me to my next destination. The airplane had landed safely, but an indicator light showed a less than completely safe status. Scientific logic would point to a malfunctioning light and not to an unsafe landing gear. But in aircraft safety regulations, something is assumed unsafe unless proven otherwise. Is it time to apply this principle to other parts of the scientific field? Should this philosophy be applied when circumstantial evidence is beginning to accumulate? Shouldn’t the scientist point out such evidence even if it does not conform to
the accepted scientific certainty principle? Whenever that 95% certainty is achieved, it might be too late to save the patient. As the judge in the Ethyl case stated, “While awaiting such statistical certainty may constitute the typical mode of scientific behavior, its appropriateness is questionable in environmental medicine, where regulators seek to prevent harm that often cannot be labeled ‘certain’ until after it occurs.” D. Deumling, Association for Forest Dieback Infor mat ion Wissen, West Germany
References (1) Schopfer, W.; Hradetzky, J. Lurtschadstoffe massgebliche U r s a c h e d e r Walderkrankung-eine weitere Untermauerung des Indizienbeweises. Der Forst und Holzwirt 1985, 8, 25. (2) McLaughlin, S.B. et al. Effects of Acid Rain and Gaseous Pollutants on Forest Productivity: A Regional Scale Approach. J . Air Pollut. Control Assoc. 1983, 33 ( l l ) , 104249. (3) Franzle, 0.; Schroder, W.; Vetter, L. “Saure Niederschlage als Belastungsfaktoren: Synoptische Darstellung moglicher Ursachen des Waldsterbens.” Report of the Umweltbundesamtes, West Germany, 1985. (4) Hager, H.; Kazda, M. The Influence of Stand Density and Canopy Position on Sulfur Content in Needles of Norway Spruce. Water, Air, and Soil Pollut. 1985,25, 321-29. ( 5 ) Georgii, H.W.; Rohbock, E.; Schmitt, G. “Untersuchung des atmosphariscken Schadstoffeintrags um Waldgebieten in der Bundesrepublik Deutschland.” Report of the Bundesministers des Innern, Luftreinhaltung Forschungsprojekt, West Germany, 1984. (6) Schmitt, G. The Temporal Distribution of Trace Element Concentrations in Fogwater During Individual Fog Events. In Atmospheric Pollutants in Forest Areas; Georgii, H.W., Ed.; Reidel: Dordrecht, Holland, 1986; pp. 129-41. (7) Block, J.; Bartels, U. “Ergebnisse der Schadstoffdepositions messungen in Waldekosystemen in den Messjahren 1981182 und 1982183.’’Report of the Landesausschutz fur landwirtschaftliche Forschung, Erziehung und Wirtschaftsberatung im Ministerium fur Umwelt, Raumordnung und Landwirtschaft des Landes Nordrhein Westfalen, West Germany, 1985. (8) H o f k e n , K.D.; G e o r g i i , H . W . ; Gravenhorst, G. Untersuchungen uber die Deposition atmospharischer Spurenstoffe an Buchen und fichtenwald. Eigenverlag des Instituts fiir Meteorologie und Geophysik der Universitat Frankfurt, West Germany, 1981, (9) Georgii, H.W.; Grosch, S.; Schmitt, G. Feststellung der Schadstoffbelastung von Waldgebieten in d e r Bundesrepublik Deutschland durch trockene und nasse Deposition. Report of the Bundesministeriums fur Umwelt, Naturchutz und Reaktorsicherheit, Luftreinhaltung Forschungsprojekt, Bonn, West Germany, 1986. (10) Schopfer, W.; Hradetzky, 3. Zuwachsruckgang in erkrankten Fichten-und Tannenbestanden-Auswertungsmethoden und Ergebnisse. Forstw. Cbl. 105(86), 446-70. (11) Kenk, G.; Kremer, D.; Bonaventura, D.; Gallus, M. Jahrring und zuwachsanalytische Untersuchungen in erkrankten Tannenbestanden des Landes Baden-Wurttemberg. Mitteilungen der Forstlichen ersuchs und Forschungsanstalt, 1984, 112. (12) Rohle, H. Ertragskundlich Aspekte der Walderkrankungen. Forstw. Cbl. 1985, 104, 225-42.
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