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No ecosystem type in the eastern United States is free of the effects of air pollution, according to a report released today. From streams and rivers to forests and wetlands, air pollution reduces the benefits these ecosystems provide to society, and damages human health and economies. Sulfur, nitrogen, mercury and ground-level ozone not only contaminate the air we breathe, they also enter the soil and water, causing a complex set of problems, according to scientists at The Nature Conservancy and the Cary Institute of Ecosystem Studies.

“We have yet to fully understand all the impacts of these pollutants, but what we’ve found so far is alarming,” said Dr. Tim Tear, a Nature Conservancy scientist and co-author of the report. “The problem is extremely widespread; the more we looked, the worse it seemed to get.”

The report, Threats From Above: Air Pollution Impacts on Ecosystems and Biological Diversity in the Eastern United States, assessed the impacts of four major pollutants on six ecosystem types in areas that receive some of the nation’s highest levels of atmospheric deposition (air pollution deposited to the landscape). These areas are often located downwind from large power plant, industrial and urban pollution sources. Among the concerns:

• In coastal waters, such as the Chesapeake Bay, excessive nitrogen has led to harmful algal blooms. Submerged aquatic vegetation, such as eelgrass, is known to be very sensitive to the effects of eutrophication.
• Deposition of nitrogen may make some habitats more suitable for weedy invasive plants and may make trees more susceptible to exotic pests.
• When surface waters become acidic, fish populations can decline. Research in the Shenandoah National Park demonstrated that with decreases in the natural ability of water to neutralize strong acids, fish populations will be lost.

“Across the Commonwealth and the northeast, air pollution is creating a legacy of ecological problems for Virginia’s natural areas,” said Judy Dunscomb, senior scientist for The Nature Conservancy in Virginia and a contributor to the report. “Air pollution is already exceeding the amounts that our forests, rivers and streams can handle. We need new efforts to monitor and reduce air pollutants for both human and ecological health.”

Air quality standards in the United States are determined by direct impacts to human health, with regulations targeting emission levels – what leaves tail pipes and smoke stacks. They do not take into account where airborne pollution is actually deposited in the landscape or how this pollution compromises our soil and water resources, natural habitats or the species that live in them.

The report includes a call to action for the United States to establish critical air pollution loads that are based on preserving healthy ecosystems. Critical loads identify the maximum level of pollutant deposition that ecosystems can handle before harmful effects occur. Some agencies have already established critical loads for particular landscapes, such as the nitrogen target load established at Rocky Mountain National Park.

It also calls for a more integrated and comprehensive national program for monitoring air pollution and its effects, including measurements of air, water, soil, habitats and wildlife.

The Nature Conservancy invests tens of millions of dollars each year in land protection for the purpose of conserving global biological diversity. Last month it announced the largest private land conservation sale in U.S. history, an agreement to purchase 320,000 acres of forestland for $510 million. But habitats and landscapes cannot be conserved by land protection alone – action to reduce air pollution must be part of the solution.