Colorado Mountains Bouncing Back From ‘Acid Rain’ Impacts Caused by Vehicle Emissions

Niwot Ridge

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Meadows, forests and mountain ridges produce the high alpine landscapes of Niwot Ridge in the Rocky Mountains, 25 miles northwest of Boulder, Colorado. Credit: William Bowman

A long-lasting pattern of environmental enhancement is appearing in the mountains west of Boulder. Researchers from CU Boulder have actually discovered that Niwot Ridge—a high alpine location of the Rocky Mountains, east of the Continental Divide—is gradually recuperating from increased level of acidity brought on by automobile emissions in Colorado’s Front Range.

Their results program that nitric and sulfuric acid levels in the Green Lakes Valley area of Niwot Ridge have actually typically reduced over the past 30 years, specifically considering that the mid-2000s. The findings, which recommend that alpine areas throughout the Mountain West might be recuperating, are released in the Journal of Geophysical Research: Biogeosciences.

This is great news for the wildlife and wildflowers of Rocky Mountain National Park to the north of Niwot Ridge, which depend upon restricted levels of level of acidity in the water and soil to flourish. Colorado’s Rocky Mountains are likewise the source of a great deal of water for individuals residing in the Mountain West, and the stability of these environments affects both the amount and the quality of this water.

“It looks like we’re doing the right thing. By controlling vehicle emissions, some of these really special places that make Colorado unique are going back to what they used to be,” stated Jason Neff, co-author on the paper and director of the Sustainability Innovation Lab at Colorado (SILC).

Almost every location worldwide, consisting of Colorado’s Rocky Mountains, has actually been impacted in the past 200 years by increased acidic nutrients, like nitrogen, consisted of in rain and snow. Nitrogen oxides, like nitrate, are produced mainly from cars and energy production. Ammonium is a primary component in typical farming fertilizers.

Nitrogen is a basic nutrient needed in environments. But when nitrogen levels increase excessive, this altered soil and water chemistry can make it hard for native plants to flourish or perhaps endure—causing a waterfall of unfavorable effects.

Niwot Ridge in the Rocky Mountains

Forty percent of the City of Boulder’s water is sourced from the Green Lakes Valley within Niwot Ridge, which the scientists examined in this research study. Credit: William Bowman

In the summer season, the sun warms up the Eastern flanks of the Front Range, triggering the warmer air to increase—bringing nitrogen from automobiles, market and farming with it. As this air cools, it forms clouds over the Rocky Mountains and falls back down as afternoon thunderstorms—transferring pollutants, discussed Neff.

In the 1970s, so-called “acid rain” hit East Coast environments much more difficult than the Mountain West, notoriously erasing fish populations and eliminating trees throughout big swaths of upstate New York. But researchers are still working to comprehend how increased levels of acidic nutrients impact the alpine area and for how long these environments require to recuperate.

To fill this space of understanding, the scientists examined information from 1984 to 2017 on climatic deposition and stream water chemistry from the Mountain Research Station, a research study center of the Institute of Arctic and Alpine Research (INSTAAR) and CU Boulder situated on Niwot Ridge. They discovered that around the early 2000s, levels of nitric and sulfuric acid stopped increasing in the Green Lakes Valley. In the mid-2000s they began reducing.

Their findings were not all great news, nevertheless. Levels of ammonium from fertilizer have actually more than doubled in rains in this location in between 1984 and 2017, suggesting a requirement to continue monitoring this farming chemical and its results on the mountain community.

From field work to stats

This work develops on years of field work by Colorado scientists at CU Boulder and beyond.

Niwot Ridge is among 28 Long Term Ecological Research (LTER) Network websites in the U.S., moneyed by the National Science Foundation. Its 4 square miles extend from the Continental Divide down to the subalpine forest, 25 miles northwest of Boulder. Researchers at CU Boulder, along with Colorado State University and the United States Geological Survey, have actually been gathering information here considering that the mid-1970s, treking through snow, sleet and rain to get it.

In the 80s, 90s and 2000s they worked to accentuate increasing acidification in Colorado mountain environments as a requirement for contamination policy in the Front Range.

This brand-new research study was enabled by these devoted researchers, tensions Neff.

“We used water quality modeling and statistical approaches to analyze the long-term datasets that Niwot researchers have been collecting for decades,” stated Eve-Lyn Hinckley, a co-author on the paper and fellow of INSTAAR. “The data are available for anyone to download. Our modeling approaches allowed us to evaluate the patterns they hold in a rigorous way.”

Since 1990, Bill Bowman, director of the Mountain Research Station and a teacher of ecology and evolutionary biology, has actually been checking out how nutrients like nitrogen impact plants in mountain environments. He’s discovered that alpine environments are distinct in how they react to these nutrients.

“It’s a system that is adapted to low nutrients, as well as a harsh climate and a very short growing season—and frost in the middle of the season. These are very slow growing plants. And they just simply can’t respond to the addition of more nitrogen into the system,” stated Bowman, likewise a fellow in INSTAAR. 

He has actually likewise discovered that these environments recuperate rather gradually, even after acidic components like nitrogen are no longer being included. But like Neff, who finished his undergraduate honors thesis with Bowman in 1993 utilizing Niwot Ridge information, he sees this research study as motivating.

Even if it’s sluggish going, they stated, these outcomes reveal that the community has an opportunity to recuperate.

“We still have air quality issues in the Front Range. But even with those air quality issues, this research shows that regulating vehicle and power plant emissions is having a big impact,” stated Neff.

Reference: “Long‐Term Trends in Acid Precipitation and Watershed Elemental Export From an Alpine Catchment of the Colorado Rocky Mountains, USA” by John T. Crawford, Eve‐Lyn S. Hinckley and Jason C. Neff, 9 November 2020, Journal of Geophysical Research: Biogeosciences.
DOI: 10.1029/2020JG005683

Additional authors on this paper consist of lead author John Crawford of the Institute of Arctic and Alpine Research (INSTAAR) and CU Boulder.

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