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CORVALLIS - While the effect of air pollution on human health gets most of the headlines, the impact of pollutants such as acid rain, ozone and other compounds on crops, forests and other vegetation is also a serious concern and the monitoring of this problem is grossly inadequate, researchers say.

Studies have shown depressed crop yields in rural parts of the United States from ozone levels that are fairly common during the summer. Forest soils may be accumulating acids from decades of sulfur and nitrogen deposition. And little is being done to even monitor these and many other problems, let alone address them, said Beverly Law, an associate professor of forest science at Oregon State University.

Law was the primary ecologist on a panel of 27 experts on the National Research Council of the National Academies, which recently issued a report on air quality issues and laws in the U.S. The panel concluded that many anti-pollution laws are outdated and inadequate, and that progress made to control emissions, despite the expenditure of $500 billion or more in one 20-year period between 1970-90, is being offset by increasing economic and population growth.

"Many people don't realize the impact that pollutants can have on crops, forests and other vegetation," Law said. "We've clearly documented some problems, but the real issue at this point is that we're doing very little monitoring to study the scope of this issue, especially in remote areas or across whole airsheds."

The nation needs a more comprehensive monitoring plan, Law said, that considers a wide range of air pollutants which may work in concert to cause environmental problems. Most past studies have looked at pollutants in isolation and not examined their combined effects. More field-based experiments are needed to couple with atmospheric models, and provide a better picture of the overall impact of air pollution on forests, crops, soils and water, she said.

"We've probably done the most work with ozone, a pollutant that some plants are more sensitive to than others," Law said. "Some areas of the Sierra Nevada mountains, for instance, have been shown to suffer leaf damage to Ponderosa pine and other conifer species. These areas are actually our nation's greatest experiment in air chemistry. With the impact from ozone, other oxidants, nitrogen as aerosols, and acid rain, the result at the ecosystem level has been a shift in species composition from pine-dominated and fire resistant species to white fir-dominated and fire susceptible species."

Studies done with agricultural crops have demonstrated that plants protected from excess levels of ozone did far better than those exposed to higher levels, Law said. These problems have been going on for a long time, she said - injury to pines in the Sierras has been noted since the early 1960s and the crop research was from the late 1970s and early 1980s.

The Clean Air Act and other environmental measures designed to monitor and prevent air pollution often make little or no mention of the effect at the overall ecosystem level. And even when steps are taken to address the issue, Law said, too often it's considered acceptable just to "make progress," rather than deal with the broad scope of the problem.