National parks are supposed to be protected tracts of American wilderness, as it existed before we cut down, farmed and paved over the bulk of it. But, according to new research, airborne agricultural byproducts are threatening the parks’ health and purity.
Scientists have long measured the impact of waterborne pollution from farms—agricultural runoff that, for instance, dumps nutrients into the ocean, feeding algae blooms that make it impossible for other animals to thrive. But heavy use of manures and fertilizers also vents gases, such as nitrogen oxides and ammonia. Normally these chemicals would help plants to grow, but if their concentrations are too high they can harm the plants, says the Los Angeles Times. And that’s what’s happening in the parks:
Thirty-eight of 45 national parks examined by scientists are receiving doses of nitrogen at or above a critical threshold that can harm sensitive ecosystems, such as lichens, hardwood forests or tallgrass prairie, scientists found.
“Changes to lichen communities may signal the beginning of other ecosystem changes that can eventually alter the function and structure of the community as a whole,” the study says.
There have been pollution problems in national parks for a long time, wrote Smithsonian Magazine in 2005, explaining how haze overtook Big Bend National Park in the 1980s. And heavy agricultural areas like California’s San Joaquin Valley, with lots of truck traffic and other equipment, on top of the fertilizer and other emissions, are big polluters, wrote Smithsonian‘s Surprising Science blog.
In this case, says the Times, the problem is probably only going to get worse.
While nitrogen oxide emissions from automobiles and power plants are on track to decline by as much as 75% by 2050, the study projected, ammonia from agriculture could rise by up to 50% as the U.S. population grows, requires more food and uses more fertilizer and livestock.
”Right now there is no effort to control ammonia emissions in this country, no regulations of any kind,” Jacob said. “If we’re going to protect our national parks from the harmful effects of nitrogen deposition we’re going to have to do something about it.”
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