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known, but all theories include an air pollution component. Root damage and leaf damage appear to interact, affecting the ability of the trees both to take up water from the soil and to retain it in the foliage, so that they become particularly vulnerable to dry spells and other stresses. Europe may be experiencing an immense change to irreversible acidification, the remedial costs of which could be beyond economic reach. (See Box 7–3.) Although there are many options for reducing sulphur, nitrogen, and hydrocarbon emissions, no single pollutant control strategy is likely to be effective in dealing with forest decline. It will require a total integrated mix of strategies and technologies to improve air quality, tailored for each region.

38. Evidence of local air pollution and acidification in Japan and also in the newly industrialized countries of Asia, Africa, and Latin America is beginning to emerge. China and the Republic of Korea seem particularly vulnerable, as do Brazil, Colombia, Ecuador, and Venezuela. So little is known about the likely environmental loading of sulphur and nitrogen in these regions and about the acid-neutralizing capacity of tropical lakes and forest soils that a comprehensive programme of investigation should be formulated without delay.

39. Where actual or potential threats from acidification exist, governments should map sensitive areas, assess forest damage annually and soil impoverishment every five years according to regionally agreed protocols, and publish the findings. They /…