National parks are protected by the federal government and carefully managed, so it’s easy to assume that they’re safe from the harm of human activity. Unfortunately, new research shows that many parks across the country are vulnerable to nutrient pollution caused by agricultural operations. A study published in the journal Atmospheric Chemistry and Physics showed that 38 of the 45 national parks examined are saturated with levels of nitrogen past the threshold that can sustain organisms in sensitive ecosystems such as hardwoods, lichens, and prairie grass.
The study, led by Harvard University professor Daniel Jacob, investigated the amounts of nitrogen oxides and ammonia released from agriculture, power plants, and vehicle exhaust. They saw that these compounds were spread to national parks via air currents across the United States. Levels were highest in parks situated close to industry, traffic, or large farms. They pointed to Cuyahoga Valley National Park, Sequoia National Park, and the Great Smoky Mountains National Park as the most critically affected.
While plants do require nitrogen to grow, too much of the element can cause harmful algal blooms, give competitive advantages to exotic species, increase the acidity of water, and disrupt the nutrient cycles. Stricter air pollution regulations have reduced the amounts of nitrogen oxides from fuel, but the levels of ammonia from livestock and fertilizers have increased. As the population of the United States grows, the researchers predict ammonia from farms could increase by 50%. There are currently no strict federal regulations to deal with ammonia emissions.