Bits of ammonium - a nitrogen compound associated with agricultural operations and fertilizers - are hitchhiking on the snow and rain that fall onto Yellowstone, Glacier and other national parks in the intermountain West.

In high enough levels, ammonium can trigger subtle changes in the natural functions of lakes, ponds, insects and flowers.

Yellowstone and Glacier are among nine parks where "significant worsening trends" of ammonium in the air were found, according to a recent National Park Service report on air quality trends from 1996 to 2005.

In Colorado's Rocky Mountain National Park, scientists studying the effects of increasing ammonium for years are starting to see shifts on the alpine tundra, where wildflowers are giving way to grasses.

That not only reduces the diversity of plants and impedes the growth of one of the park's main summer visitor attractions, but also could have a harmful effect on pollinating insects.

Scientists are watching for other changes, too, including to forests in the park and to tiny life forms that live in high-elevation lakes.

"What we're experiencing now could easily be something that Yellowstone could see in the future," said Jeff Connor, a natural-resource specialist at Rocky Mountain National Park.

For now, though, Rocky Mountain park has higher levels than Yellowstone or Glacier.

Overall, the air quality in Yellowstone still good. Visibility is improving and the presence of ground-level ozone - listed as a concern for several years in the trend studies - appears to have leveled off.

But over the past several years, monitors have been picking up more and more ammonium in the air in Yellowstone and elsewhere.

"The real question is why it's increasing. ... It's not just in Yellowstone, it's up and down the western Great Plains," said John Vimont, chief of research and monitoring in the Park Service's air resources division in Denver. "We really don't know what the answer is."

Full Story: http://www.billingsgazette.net/articles/2007/12/22/news/state/21-rainfall.txt