Titled "Threats From Above: Air Pollution Impacts on Ecosystems and Biological Diversity in the Eastern United States", the report is the first to analyze the large-scale effects that four air pollutants are having across a broad range of habitat types.
"Everywhere we looked, we found evidence of air pollution harming natural resources," said Dr. Gary M. Lovett, an ecologist at the Cary Institute and the lead author of the report. "Decisive action is needed if we plan on preserving functioning ecosystems for future generations," he added.
Pollutants poison areas far from their point of origin.
The pollutants assessed - sulfur, nitrogen, mercury, and ground-level ozone - largely originate from smokestacks, tailpipes, and agricultural operations. While initially airborne, these pollutants eventually return to the landscape, where they contaminate the soil and water.
Airborne emissions can travel long distances before making their way back to the ground.
Because the eastern United States is downwind from large industrial and urban pollution sources, it receives the highest levels of deposited air pollution in North America.
This is bad news for vulnerable wildlife, forest productivity, soil health, water resources, and ultimately, economies.
According to Co-author Dr. Timothy H. Tear, of The Nature Conservancy, deposited pollutants have tangible human impacts.
"Mercury contamination results in fish that are unsafe to eat. Acidification kills fish and strips nutrients from soils. Excess nitrogen pollutes estuaries, to the detriment of coastal fisheries. And ground-level ozone reduces plant growth, a threat to forestry and agriculture," he said.
New air quality standards are critical to protecting natural resources.
Currently, U.S. air quality standards 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 and resident plants and animals.
"To safeguard ecosystem health, we need a new way of thinking about air pollution - one that moves beyond measuring what is put up in the air, and captures actual impacts to natural areas, wildlife, and the services they provide," said Lovett.
The authors urge US policymakers to establish air quality standards that are based on critical loads. This is defined as the maximum level of deposited pollution that ecosystems can tolerate before harmful effects occur.
By establishing thresholds, pollutants can be regulated in a way that preserves functioning ecosystems.