(FORTUNE Magazine) – A reasonably attentive follower of the acid rain controversy might well have concluded in March that the case was closed -- that there was no longer a scientific controversy. The Reagan Administration was certainly acting as though it had reached some such conclusion. After years of insisting that more research was needed before it would act, the Administration formally accepted the view that acid rain is a big problem, that it is rooted in industrial emissions, and that something must be done to prevent these emissions from drifting over the Canadian border. Ronald Reagan has also bought a proposal, previously endorsed by the Canadian government, that the U.S. spend $5 billion over five years to develop ways of limiting emissions. In recounting this story the other day, the New York Times had this to say about our knowledge of acid rain: ''A scientific consensus says these (emissions) are considered responsible for damage to freshwater lakes and streams. They may also damage trees and plant life and human health.'' To those who have monitored the scientific evidence about acid rain's environmental effects, the goings on in Washington are astonishing. Much is still unknown about acid rain's dimensions and effects, and that ''consensus'' in the Times is nonexistent. But to the extent that science has been participating in the debate, it has been telling us we have less reason to be concerned about those industrial emissions than previously supposed. Some recent analyses have suggested that acid rain is only a minor contributor to the environmental damage (the extent of this damage being itself a matter of great uncertainty). So far as the lakes are concerned, the principal sources of damage are likely to be natural sources of acid. In fact, acid rain has never been conclusively shown to be the principal cause of any of the environmental problems it's accused of causing. These are among the findings of a major Hudson Institute study published several weeks ago. It has always been clear to the scientific community that the claims of acid rain damage were based on circumstantial evidence: you could point to industrial emissions and you could point to acidified lakes. Efforts to gain a more direct knowledge of cause and effect have repeatedly been frustrated. In the U.S., the federal government established a National Acid Precipitation Assessment Program (NAPAP) in 1980. Initially budgeted at $17 million -- a figure that has grown to a proposed $85 million in fiscal 1987 -- NAPAP has made the first serious effort to determine the degree to which acid rain may be responsible for damage; most earlier research assumed that acid rain was the cause of environmental damage and was concerned only to ascertain how the process worked. The findings of the new program have called into question the accepted earlier notion that rivers, lakes, trees, and forests were being ''killed'' by acid rain. The media have repeatedly served up certain simple images about acid rain -- images that are easy to understand, and therefore easy to believe. We are all familiar with the image of acid rain falling on the land area above some lake, after which it flows into and acidifies the lake, killing the fish. All very clear, simple, and misleading. The NAPAP scientists and others have focused on three main questions about the acidification of U.S. lakes: (1) Has there been a significant increase in lake acidity over time? (2) Might something other than acid rain be contributing to lake acidification? (3) Might something other than acidity be affecting the survivability of the fish? Getting solid answers to these questions is not easy. For example, a lake's acidity can vary with the time of day, the season, the amount of prior rainfall, the temperature and cloud cover, the depth and distance from the shore at which samples were taken, and much more. Not surprisingly, successive acidity measures of a particular lake can vary by a factor of 100. BUT WHAT ABOUT those relatively acidic lakes without any fish populations? Don't they support the claim linking acid rain to stresses in aquatic systems? It is not clear that they do. For one thing, nobody seems able to prove that the number of lakes without fish is greater now than it was several decades ago. Nor has it been proven that where fish populations clearly have disappeared, the change reflects acidification. A major problem confronting researchers is the paucity of past data to use as a base line. And there is some evidence that fishless lakes in the Adirondacks were a major concern over 60 years ago. Has the number of fishless lakes in the U.S. increased since then? We simply do not know. In any case, only about 200 such lakes have been identified -- all of them in the Adirondack Mountain region of New York. It happens to be a region in which the vegetation and geology predispose aquatic systems toward natural acidification. The amount of acid generated by nature is now known to be far greater than that contributed by industrially generated acid rain. Take bird droppings, which are a relatively minor contributor to the problem. A calculation based on Audubon Society data shows that the droppings hit the U.S. at a rate of about one million per second, and the 150 million tons of droppings per year outweigh sulfur dioxide emissions by something like six to one. Soil scientists, largely ignored in acid rain research before 1980, have long known that the acidity of water in soil is essentially determined by properties of the soil through which it moves, not by the acidity of the rainfall. Precipitation that gets down to the mineral layers of watersheds before entering a lake tends to lose acidity; conversely, precipitation that makes contact only with the topsoil tends to become more acidic. The humus layer in Eastern watersheds can increase the acidity of rainfall tenfold. What about the effect of acid rain on our forests? Here again the media have given a simple and misleading story. The story tends to take its direction from a widely publicized hypothesis offered in 1982 by botanist Hubert Vogelmann of the University of Vermont, who suggested acid rain as the reason for a so-called dieback among spruce trees on Camels Hump, a Vermont mountain peak. But since 1982 the international scientific community has registered skepticism about the basic hypothesis, and many investigators today even doubt that acid rain is the primary suspect in the claimed forest damage. Some investigators even question whether any unusual amount of damage is occurring. But even assuming that the damage is abnormal, scientists today tend to look also at the impact of such natural stresses as droughts, frosts, insects and pathogens, combined with ozone, heavy metals and other air pollutants. Several other accusations have been leveled against acid rain, including its possible detrimental effect on human health, on crops, and on building materials. It is understandably easy to confuse the damage attributed to acid rain with that caused by ozone, sulfur dioxide, ammonia, nitrogen oxide, and other pollutants. To what degree are such claims improperly directed against acid rain? NAPAP's huge research program does not yet have all the answers to that question, but the preliminary findings are suggestive. Clearly we can reject the claims about acid rain causing many premature deaths. The claim that acid rain damages important crops appears almost as frivolous. Of the many experiments performed, only a rare few gave any support at all to the claim. These experiments have led the Environmental Protection Agency to conclude that the effects of acid rain on crops are as likely to be positive as negative but are minimal in either case. Many scientists in the past found it plausible that acid rain significantly degrades various exposed structures and materials. But most of the NAPAP analyses dispute this view, suggesting instead that natural weather conditions (especially freeze-thaw cycles) and several air pollutants cause the damage. One important finding of the NAPAP scientists is that most urban pollution comes from local emissions, not from distant emissions borne by rainfall. The evidence suggests that attempts to reduce the impact of pollutants on exposed structures in urban areas should focus on local automobiles and buildings and on nearby industries. NONE OF THE ABOVE is meant to suggest that the scientific community is agreed about acid rain's environmental impact. If anything scientists are more polarized than ever about the issue. Debates reflecting that polarization within the National Academy of Science evidently caused a delay of about ten months in the publication of its most recent report on acid rain issues, which ended up being endlessly hedged and qualified about major matters. I believe that the urge to control acid rain stems from beliefs that once seemed intuitively plausible but that have been made obsolete by most of the recent evidence. I do not know why the Reagan Administration is bowing now to the political pressures to ''do something'' about acid rain. Perhaps the Administration is simply recognizing that just about everybody wants to reduce industrial emissions and that the steps contemplated under the new $5-billion program (half of which will be financed by the private sector) could be justified even if those emissions are not really acidifying our lakes and forests. Perhaps the program is viewed as a reasonable accommodation to a conservative Canadian government; there is no doubt that the acid rain issue, propelled in some measure by anti-Americanism, has a lot of emotional firepower behind it in Canada. Whatever the President's reasons, Americans shouldn't read the news as evidence that acid rain is the monstrous problem it's made out to be.