A phenomenon called "accidental fertilization" has been bad news for America's national parks, and scientists don't predict an improvement before the year 2050.
The problem occurs when nitrogen-based compounds are "blown" into parks, these compounds can come from sources like: automobile exhaust, power plants, and industrial agriculture, a Harvard University news release reported.
"The vast majority, 85 percent, of nitrogen deposition originates with human activities," principal investigator Daniel J. Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), said. "It is fully within our power as a nation to reduce our impact."
When the nitrogen pollutes national parks, the nitrogen can disrupt nutrient cycles in the soil. The pollution can also lower the pH of water and cause an overpopulation of algae blooms, which could keep other species from thriving.
Regulations on air pollution and new "green" technology are working to reduce the concentrations of harmful nitrates in the atmosphere given off by plants and automobiles. There are currently no regulations on the amount of ammonia released into the atmosphere by the agriculture industry and animal waste. Agriculture is believed to contribute one-third of all atmospheric nitrogen pollution.
"Ammonia's pretty volatile," Jacob said. "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."
Researchers calculated the "nitrogen deposition rates" across the states and found many parks are already feeling the consequences of the pollution.
In areas such as the Great Smoky Mountains National Park, the hardwood trees suffer when nitrogen deposition reaches about three to eight kilograms per hectare, per year. The study found that has already been exceeded, and the deposition rate is currently 13.6 kg/ha/yr.
In the Mount Rainier National Park the lichen is suffering from nitrogen pollution.
"The lichens might not be noticed or particularly valued by someone walking around a national park, but they're integral for everything else that's dependent on them," lead author Raluca A. Ellis, who conducted the research as a postdoctoral fellow at Harvard SEAS and now directs the Climate and Urban Systems Partnership at the Franklin Institute, said.
The researchers predicted nitrogen emissions in the U.S. will decrease by 2050. The same cannot be said for ammonia pollution
"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. When you try to write regulations to protect ecosystems, however, the damage is much harder to quantify," Jacob said. "At least in the national parks you can say, 'There's a legal obligation here.'"
