National Parks Under from Unregulated Agricultural Ammonia

National parks throughout the United States are undergoing "accidental fertilization" at or above the threshold recognized for causing ecological damage -- a result of nitrogen-based compounds blown in from power plants, car exhaust and industrial agriculture.

Such were the findings of a recent study published in the journal Atmospheric Chemistry and Physics. According to the report, unless significant controls are placed on ammonia emissions throughout the nation, the situation is not liable to improve.

Nitrogen is known to disrupt the cycling of nutrients in soil, promote algal overgrowth, lower the pH of water and overall restrict the number of species able to survive in an area.

"The vast majority, 85 percent, of nitrogen deposition originates with human activities," said principal investigator Daniel Jacob, a professor of atmospheric chemistry and environmental engineering at the Harvard School of Engineering and Applied Sciences (SEAS). "It is fully within our power as a nation to reduce our impact."

Existing regulations and trends are set to reduce the amount of harmful nitrogen oxide emitted by cars and power plants, the researchers note; however, no government regulations limiting the amount of ammonia emitted through agricultural fertilization or manure from animal husbandry -- together responsible for one-third of the manmade nitrogen carried by air currents -- currently exist.

"Ammonia's pretty volatile," Jacob explained. "When we apply fertilizer in the United States, only about 10 percent of the nitrogen makes it into the food. All the rest escapes, and most of it escapes through the atmosphere."

According to the researchers, which also include scientists from the National Park Service, USDA Forest Service, and US Environmental Protection Agency and the University of California, Irvine, many parks may already feel the effects of the pollution.

When it comes to the Eastern temperate forests like those in the Great Smoky Mountains National Park, hardwood trees are the most sensitive, showing signs of struggle when nitrogen deposits reach approximately 3 to 8 kilograms per hectare annually. According to the study, the actual rate of deposition has reached 13.6 kilograms annually.

"Air quality regulations in the United States have always focused on public health, because air pollution leads to premature deaths, and that's something you can quantify very well," Jacobs said. "When you try to write regulations to protect ecosystems, however, the damage is much harder to quantify. At least in the national parks you can say, 'There's a legal obligation here.'"