Call it the Goldilocks principle: Nitrogen fertilizer helps out plants in small quantities, but as is often the case, too much of a good thing can be bad.
New research from Harvard University shows that 38 out of 45 national parks receive “accidental fertilization” in the form of nitrogen-based pollution at or above levels known to cause harm to the flora in their ecosystems, such as lichens, hardwood forests, and tall grass prairie.
The “fertilizer” is blown into the parks from nearby power plants and industrial agriculture operations, and from automobile exhaust, according to the study, which was published last week in the journal Atmospheric Chemistry and Physics.
The Great Smoky Mountains National Park, Cuyahoga Valley National Park, and Sequoia National Park are among the most threatened parks, said Daniel Jacob, a professor of atmospheric chemistry at Harvard.
While nitrogen is an essential for plant growth, too much of it can disturb the cycling of nutrients in soil, lower the pH of water, and foster the growth of algae in waterways, which use up oxygen when they die, hurting fish and other aquatic life. This particular problem has already been observed in Rocky Mountain National Park, the study notes.
While most of the pollution that blanketed the surveyed parks was nitrogen oxide, a chemical-compound that’s spewed into the air by cars and trucks burning gasoline and diesel, a large percentage of the waste was also found to be ammonia, which is used to fertilize crops, and is present in manure.
The problem with ammonia is that it's a volatile chemical and much of it evaporates before plants can take it up. Only about 10 percent of the ammonia used in agriculture actually makes its way into food, Jacob said.
While emissions of nitrogen oxides are falling, due to more stringent regulations by the U.S. Environmental Protection Agency, ammonia emissions, mostly from agriculture, are on the rise. These are expected to climb by up to 50 percent by 2050, according to the study. And even if emission of nitrogen oxides fell to zero, ammonia emissions would need to be cut 55 percent by 2050 to not exceed harmful levels in national parks, according to the study.
"We are trying to clean up our combustion emissions, but we're doing nothing about ammonia emissions," Jacob says.
One way to reduce these emissions would be to avoid exposing manure to the open air, and changing the way ammonia is applied to farm fields.
The struggle is to quantify the effect on plants and put a dollar figure on it. That's easier with nitrogen oxides, like nitrogen dioxide, since these gases can have a negative impact on human health, which is why the EPA has made it a priority to reduce them. In fact, one of the reasons Jacob and his colleagues conducted their study in national parks is that the health of these ecosystems is protected by federal law. So the study could be used to help establish regulations to reduce ammonia emissions.
And there's evidence that forests are already being harmed. The actual rate of nitrogen deposition in national parks is currently four times higher than the minimum threshold known to hurt hardwood trees, according to the study.
"The damage to the system is taking place all around the country," and is threatening national parks, said Jacob. "We should try to do something about it."
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Original article from TakePart