Trend worsening for pollutant in 16 national parks

By MIKE STARK - Associated Press Writer

Air quality data obtained by The Associated Press shows significant worsening trends for ammonium in several flagship parks, including Yellowstone, Mount Rainier and Utah's Canyonlands. At Colorado's Rocky Mountain National Park, researchers have already seen subtle shifts in the alpine tundra, where some of the park's trademark wildflowers are being replaced by grass. Read more