In both the United States and parts of Europe, the pressure is on to ''do something'' about acid rain. Germany is cracking down on industrial emissions of sulfur on the unproven assumption that they threaten its forests, the Black Forest in particular. In the United States, the White House Office of Science and Technology Policy (OSTP) urges immediate action to curb such emissions ''despite incomplete knowledge of the [acid rain] problem.''
There may be wisdom in this approach. But where ignorance is the guide to action, you can never be sure the action will, in fact, solve the problem. Policymakers are apt to shoot at the wrong target. There is great potential for public disappointment.
Some experts now warn that this is likely to be the case with acid rain.
There seems little doubt that industrial emissions of sulfur and nitrogen oxides (especially from power plants) cause acid rain, as a US National Academy of Sciences committee reported in late June. But it is by no means clear that acid rain is doing much damage to lakes and rivers, forests and soils - which is the major concern.
Edward C. Krug and Charles R. Frink of the Connecticut Agricultural Experiment Station explained recently in Science that natural processes of soil formation can be a much more important factor. For many hard wood and conifer forests, such processes create strongly acid soils. The two scientists note that , in areas of greatest concern such as the Northeastern United States and Scandanavia, the strong recovery of forests from cutting and burning in previous centuries has led to new growth of highly acid soils. Runoff through such soils then acidifies lakes and streams.
The two scientists do not deny that acid rain does sometimes acidify soils and lakes directly. But they note that, in many cases, a complete cutoff of acid precipitation wouldn't halt acidification.
King and Frink conclude that ''the hypothesis that increased deposition of acid and sulfate is causing equivalent leaching and acidification is theoretically unsound and is not supported by direct observation. Natural processes of acidification must be more carefully considered in assessing the benefits expected from proposed reductions in emissions of oxides of sulfur and nitrogen.''
British ecologist Kenneth Mellanby makes the same point in reporting in Nature on a recent acid rain conference in West Germany. Mellanby is former director of Britian's Monks Wood Experimental Station, an environmental laboratory, and is now editor of the journal Environmental Pollution.
Referring specifically to forest damage in West Germany, Mellanby says it is so far confined to fairly small local situations but that there is the possibility that it might spread rapidly. Having said that, he further notes that there were ''few supporters for the view that acid precipitation had been proved to be the only or even the main culprit.''
He also notes that Norwegian studies show ''that acidification was often dependent on changes in land use rather than on precipitation,'' which is Krug's and Frink's point. After visiting the Black Forest, Mellanby says it is ''certain'' that damage there cannot be due to sulfur emissions in West Germany because the sulfur dioxide levels in the forest ''are very low indeed.''
''So,'' Mellanby adds, ''the policy of the German government . . . to reduce sulfur output from their industry to low levels, at a very considerable expense, may be, on a global scale, very altruistic, but it will not do any good (or any harm) to the trees of the Black Forest.''
This is not to say that sulfur emissions and acid rain are benign. They may well need to be severely curbed, especially in the US. But neither the Congress nor the public in affected regions such as the Northeast should expect the decreases to solve the problem of sour lakes and acidifying soils.
In fact, present legislation in Congress aimed at cutting sulfur exports from the Midwest may not be the best way to curb acid rain itself. For one thing, some 40 percent of the rain's acid is due to oxides of nitrogen. So curbing sulfur only gets at part of the problem.
Secondly, imposing smokestack controls indiscriminately on Midwestern industry may be needlessly costly. A report from the Massachusetts Institute of Technology's Energy Laboratory favors selective regulation. That means identifying individual polluting plants and controlling them.
More important, as explained by MIT's James Fay, Dan Golomb, and James Gruhl, controlling stack emissions of existing plants is not the best long-term strategy. The most effective way to control acid rain, they say, is to use new burners specifically designed not to produce the offending emissions. That can mean scrapping existing plants and building news ones - hardly an efficient therapy.
Here again, the message is not to expect too much from the hasty implementation of policy based at least partly on ignorance.
In the short run, it is probably wise to control some stack emissions, switch to low sulfur fuels where possible, and use similar temporary measures to cut acid emissions. But the overall control strategy has to include realistic assessments of the true environmental effect of acid rain. Then the value of building acid-free furnaces can be intelligently assessed.
Meanwhile, priority should be given to gaining the scientific knowledge, now so badly needed, on which a truly sound acid rain policy can be based.