From The Grand Junction Daily Sentinel (Dennis Webb):
Fewer alpine wildflowers and shifts in the biology of mountain lakes are among the changes occurring in Colorado’s high country due to increasing levels of atmospheric nitrogen, a scientist studying the issue says…
The problem of nitrogen pollution in air and water serves as a reminder that climate change isn’t the only kind of global change, she said last week at the weekly winter Naturalist Nights speaker series. Things such as land-use changes and nitrogen pollution can wreak havoc on things such as biodiversity as well.
Nitrogen pollution comes from numerous sources, from livestock manure to overfertilization to fossil-fuel combustion, and is generally worse in the eastern United States than in the West. It’s a potent greenhouse gas, a contributor to ozone pollution, and excess amounts in drinking water cause cancer and blue-baby syndrome, Baron said. In surface waters it can result in low-oxygen biological “dead zones” due to excessive nutrients contributing to rampant algae growth.
Fortunately, water in Colorado’s mountains isn’t threatened by runoff from agricultural-related operations because the mountains sit higher than ag operations, she said.
“What we have is what falls out of the sky,” Baron said.
This has led to higher nitrogen levels in places like Rocky Mountain National Park, as warming morning air rises into the mountains from the Front Range and draws up nitrogen from the abundant human sources there. Nitrogen can be deposited in rain during afternoon storms that often follow. Unfortunately, Baron said, Colorado’s relatively poor soil and short growing season means there’s little vegetation to take up and store nitrogen.
Excess nitrogen acts as a fertilizer in the alpine environment, and that means some plants are winners and some are losers. She said grasses and sedges take advantage of the fertilizer to grow faster than wildflowers and crowd them out. Likewise, invasive cheatgrass at lower elevations responds well to higher nitrogen levels, she said.
Increased nitrogen in needles can make evergreens more attractive to insects that like to eat needles, but fortunately that hasn’t been a problem to date in Colorado, she said.
Increased nitrogen in soils makes it more acidic and changes soil fungi and bacteria, and as a result what eats them, such as nematodes, mites and springtails. That can affect snails, birds and other animals farther up the food chain, she said.
Baron said that while Rocky Mountain National Park lakes are awash in nitrogen, Western Slope ones are not.
But she said adding nitrogen to lakes with little nitrogen can quickly result in a lot of algae, and also lead to algae species being replaced by different ones, some of which are poor in nutrients and invertebrates don’t like to eat as much.
She said global nitrogen pollution levels have been high for many decades, but scientists believe the effects are being amplified by global warming, in this “perfect intersection of two global changes.”
Baron takes heart in an effort between state and federal agencies to try to address nitrogen levels in Rocky Mountain National Park through pursuing reductions in vehicle emissions, and a switch from coal to natural gas and renewable power sources.
“It’s all very encouraging that people want to solve this problem,” she said.