"Nutrient Pollution Threatens National Park Ecosystems, Study Says"
"National parks from the Sierra Nevada to the Great Smoky Mountains are increasingly being fertilized by unwanted nutrients drifting through the air from agricultural operations, putting some of the country’s most treasured natural landscapes at risk of ecological damage, a new study has found."
"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."Source: LA Times, 10/15/2013