In our last column we noted that even strong conservation measures, strict control of localized pollution sources, and the protection of recharge areas would probably not be adequate to safeguard America's ground-water resources. One reason for this, of course, is that the demands of population and economic growth could easily keep withdrawal rates higher than recharge rates in spite of conservation and watershed preservation. A second factor is the potential for pollution originating in the rain itself.
Until recently, the notion of rain as a source of pollution seemed preposterous, but humanity has steadily increased its use of fossil fuels. Among the products of such combustion are oxides of sulfur and nitrogen, which are spewed into the atmosphere by automobile exhausts and factory/powerplant smokestacks. There, the oxides take part in a variety of chemical reactions, producing (among other things) sulfuric and nitric acids.
These potent acids, mixed with rainwater, are now descending upon us as acid rain. Over vast areas of North America, Europe, and Asia, rain has become 10 to 1,000 times more acid than normal. Until recently, the record was held by Pitlochry, Scotland, where in 1974 the rain was as acid as vinegar! In 1981, however, this dubious first-place award was captured by the People's Republic of China: In the city of Michin, in the center of the country, University of California scientist John Harte measured rain significantly higher in acidity than that which fell on Pitlochry.
The impact that acid rains have on aquatic ecosystems can be dramatic, especially those systems occurring in areas with granite, quartz, or similar rock. Such rocks, which have a low capacity to neutralize (or "buffer") the acidity, are widespread in the Appalachian and Rocky Mountains and throughout much of Canada, New England, and northern Europe. The lakes of southern Norway, for example, are in severe trouble. Populations of micro-organisms crucial to the lakes' economies have been altered, and fish populations have declined or disappeared.
The situation is especially critical in the Adirondacks. Not only are the rains acidifying the water there, but the sulfuric and nitric acids are causing chemical reactions in the soil that are releasing large quantities of aluminum. The acids accumulate in the snowpack in the winter. Then, when the snow melts in the spring, they pour into the lakes ... creating a flush of aluminum pollution. As a result, all fish have been killed in some 300 Adirondack lakes, and brook trout and other sensitive species may have been exterminated over the whole area. (Spotted salamanders, for example, cannot breed in acid snowmelt.)
In Canada, scientists have now identified 48,000 lakes that will become sterile in 20 years or so if the acid rains continue. And along with dams, overfishing, poaching, pesticides and other kinds of pollution, the rains threaten the economically valuable Atlantic salmon with extinction.
While the most dramatic immediate effects of acid precipitation appear in ponds and lakes, it may seriously damage terrestrial ecosystems as well. The acids can apparently harm soil micro-organisms, including those that participate in the crucial nitrogen cycle. They also can influence the rates at which toxins are mobilized in the soil. Those in turn tend to worsen the effects of other pollutants.
At the moment we cannot give accurate estimates of the damage potential of acid rains. There is evidence, for example, that they are stunting forest growth (indeed, recently it has been claimed that much of Europe's woodland is already doomed). But it may be decades before the full impact of acidic precipitation on trees will be understood. Similarly, there's laboratory evidence that some lichens may be very sensitive to this pollutant from the skies, a situation that could portend serious changes in both arctic and alpine ecosystems.
And then there's the problem of the relationship of acid rains to the quality of our surface- and ground-water supplies. What, for example, will be the long-term effects of pouring diluted acid into the soils of Long Island and other eastern regions? Much will depend on the capacity of the rocks to buffer the acid. This, in turn, will depend on both the chemical characteristics of the soil and the duration of the rains. Other effects will be determined by what materials, especially trace toxic metals, are mobilized by the acids from the soils and rocks of the aquifers.
Consider, for instance, what may happen in Colorado, where acid rain is now falling on the bare rocks of high alpine areas. Toxic metals are likely to be leached from the rocks. These, in turn, may concentrate in high alpine lakes and then in the beaver ponds of montane meadows. From there, trace metals can flow into three of the major rivers of the nation — the Colorado, the Rio Grande, and the Mississippi — where they'll join toxic metals seeping from Colorado's uranium, molybdenum, and other mining operations. As Colorado environmentalist Bob Lewis put it, we're the first nation to poison its water supply at the source.
The only solution to the acid rain problem is to reduce the emission of pollutants from burning fossil fuels. Pollution control efforts will have to be made much more efficient. Solar energy and other renewables (or, if it can ever be made acceptably safe, nuclear energy) will have to be substituted for fossil fuels. And the size of the human population will have to be controlled.
Acid rains are already causing international problems as pollution from the United States drifts over Canada and that generated by Great Britain falls in Scandinavia. Like so many other environmental problems, this one cannot be solved by local measures alone, although such measures can be enormously helpful.
Before we can expect to make much progress, though, we'll have to seek wider recognition of the seriousness of the problem. Ronald Reagan's budget director, on hearing of the destruction of the Adirondack fish populations, reputedly commented that the power plants and industries of the Ohio Valley that were causing the acid rains were much more valuable than the trout. He obviously didn't know that the rains constitute a broad-spectrum assault on ecosystems that are essential to the persistence of industrial society. (See Snail Darters and the Importance of Ecosystems) Furthermore, even considering the damage only from the director's narrow viewpoint, the economic losses in wildlife, crops, and forests are far greater than the costs of cleaning up Ohio's power plants would be. The Reagan administration in general has shown a similar lack of concern about the threat of acid rain.
John Harte (University of California at Berkeley) and Robert Lewis (Environmental Research Group, Aspen) have helped a great deal in the preparation of this column. It's also based on material in Paul and Anne Ehrlich's Extinction: The Causes and Consequences of the Disappearance of Species (Random House, 1981, $15.95), where further documentation on acid rains may be found. For a summary of the threat to Europe's forests, see Fred Pearce's "The Menace of Acid Rain"; New Scientist , August 12, 1982.
Paul Ehrlich (Bing Professor of Population Studies and Professor of Biological Sciences, Stanford University) and Anne Ehrlich (Senior Research Associate, Department of Biological Sciences, Stanford) are familiar names to ecologists and environmentalists everywhere. But while most folks are aware of the Ehrlichs' popular writing in the areas of ecology and overpopulation (most of us, for instance, have read Paul's book The Population Bomb ), few people have any idea of how deeply the Ehrlichs are involved in ecological research (the type that tends to be published only in technical journals and college texts). That's why we're pleased to present this regular semi-technical column by these well-known authors/ecologists/educators.
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