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Air Pollution Changing Plant Life in Rocky Mountain National Park




BOULDER, Colorado, July 5, 2012 (ENS) - Air pollution from power plants, automobiles and agriculture is changing the alpine vegetation in Rocky Mountain National Park, finds a new study funded by the National Park Service

Emissions of nitrogen compounds to the atmosphere are being carried to remote areas of the park, altering sensitive ecosystems, said the study's lead scientist Professor William Bowman at the University of Colorado, Boulder.

Dr. William Bowman (Photo courtesy CU-Boulder)

"The changes are subtle, but important," said Bowman, who directs the CU-Boulder Mountain Research Station located some 30 miles west of the city. "They represent a first step in a series of changes which may be relatively irreversible."

"The take-home message is that the amount of nitrogen deposition reaching the tundra in Rocky Mountain National Park has already passed an important threshold and may lead to more serious environmental impacts," said Bowman.

"It's not inconceivable that continued negative ecological impacts in the park due to nitrogen pollution could eventually impact tourism in Colorado."

In other regions of the world, higher amounts of nitrogen pollutants have led to decreased biodiversity, acidified soils and dead fish in the streams, said Bowman, a professor in CU-Boulder's Department of Ecology and Evolutionary Biology.

"There is evidence that indicates once these changes occur, they can be difficult if not impossible to reverse," he warned. "It is best to recognize these early stages before the more harmful later stages happen."

The study site was an alpine meadow about one mile east of Chapin Pass in the Mummy Range of Rocky Mountain National Park. Such ecosystems are the most sensitive to adverse impacts from air pollutants.

Over three years, Bowman and his team analyzed the plant communities and soils under ambient levels of nitrogen deposition and compared them to plots with nitrogen added to simulate the increasing atmospheric nitrogen pollution expected in coming decades.

Researchers Isabel Ashton and John Murgel analyze vegetation changes in Rocky Mountain National Park. (Photo by William Bowman)

The results indicated changes in plant abundances already are occurring under ambient conditions.

Rising levels of nitrogen in the soils correlated with large increases in a common species of sedge shown to flourish in other studies using the same nitrogen addition technique.

Bowman said he and his team anticipate that the diversity of plant species will rise with increasing nitrogen deposition, then decrease, with more rare species being excluded by competition from other plant species.

"While the changes are relatively modest, they portend that other more environmentally adverse impacts may be on the horizon in Colorado's alpine areas," he said.

Previous studies by Bowman and others have shown vegetation changes and soil acidification have been occurring due to increasing nitrogen deposition at other alpine sites in Colorado, including Niwot Ridge. This National Science Foundation-funded Long-Term Ecological Research site is administered by CU-Boulder and located next to the Mountain Research Station Bowman directs.

Over the next several decades, as the population grows in Front Range cities in the greater Denver area and farmers use more nitrogen fertilizers to grow more food for them, nitrogen deposition is expected to increase in Rocky Mountain National Park, said Bowman.

The high mountain ecosystems of the park draw thousands of visitors each year, including fishermen hoping to catch trout in pristine waters.

But continued inputs of nitrogen pollutants are a hazard to the health of both trout and their food sources, said Bowman. It starts when the ability of the land plants and soils to take up the nitrogen is exceeded, causing soils to become acidified, he said.

Other parts of the Colorado Front Range have shown signs of acidification at the highest elevations, Bowman said. "Once this happens, soluble aluminum leaches from soils and begins to show up in streams and lakes. This aluminum is quite toxic to many aquatic animals," he said.

Officials from the nonprofit groups Environmental Defense and Trout Unlimited petitioned the State of Colorado and the U.S. Environmental Protection Agency to reduce emissions of nitrogen pollution in 2004. This resulted in a 2007 plan to lower nitrogen emissions on a voluntary basis to reduce impacts to Rocky Mountain National Park.

Excel Energy's recent switch to natural gas in some of its power plants is one of many steps toward limiting nitrogen emissions, said Bowman. Ongoing efforts by air quality managers and representatives from the Colorado agricultural industry are also working on management practices that would lower nitrogen emissions.



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