- Air quality at Black Canyon of the Gunnison National Park
- Related references
Air quality at Black Canyon of the Gunnison National Park
Most visitors expect clean air and clear views in parks. Black Canyon of the Gunnison National Park (NP), Colorado, the “greatest combination of depth, narrowness, sheerness of any canyon in North America,” is in a relatively remote location on the Colorado Plateau. Still, upwind urban and industrial sources can degrade air quality at the park. Air pollutants blown into the park can harm natural and scenic resources such as soils, surface waters, plants, wildlife, and visibility. The National Park Service works to address air pollution effects at Black Canyon of the Gunnison NP, and in parks across the U.S., through science, policy and planning, and by doing our part.
Visitors come to Black Canyon of the Gunnison NP, a high desert on the Colorado Plateau, to enjoy scenic views of the deep, steep, and narrow canyon carved by the Gunnison River. Park vistas are sometimes obscured by haze, reducing how well and how far people can see. Visibility reducing haze is caused by tiny particles in the air, and these particles can also affect human health. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze. Organic compounds, soot, dust, and wood smoke reduce visibility as well. Significant improvements in visibility have been documented since the 1990’s. Overall, visibility still needs improvement to reach the Clean Air Act goal of no human caused impairment.
In the region, average natural visual range is reduced from about 175 miles (without the effects of pollution) to about 140 miles because of pollution. The visual range is reduced to below 95 miles on high pollution days.
Visit the NPS air quality conditions and trends website for park-specific visibility information. Visibility monitoring at Weminuche Wilderness has been active since 1988, and these data are considered representative of regional visibility conditions for Black Canyon of the Gunnison NP. Explore park vistas through live webcams.
Nitrogen and sulfur
Nitrogen and sulfur compounds deposited from the air may have harmful effects, including acidification, on soils, lakes, ponds, and streams. Given the abundance of base cations in underlying park soils and rocks, surface waters in Black Canyon of the Gunnison NP are generally well-buffered from acidification. However, steep-sided canyon walls in the park have little ability to retain nutrients and water, limiting the landscapes to buffer acidic run-off that may discharge to the inner canyon. The ecosystem sensitivity to acidification from nitrogen and sulfur at Black Canyon of the Gunnison NP relative to other national parks is considered high (Sullivan et al. 2011c; Sullivan et al. 2011d). Some plants are sensitive to acidification, search for acid-sensitive plant species found at Black Canyon of the Gunnison NP. Even with the presence of sensitive ecosystems and plants the estimated levels of sulfur and nitrogen deposition are so low that risk of acidification is considered minimal at the park.
Excess nitrogen can also lead to nutrient enrichment, a process that changes nutrient cycling and alters plant communities. Ecosystem sensitivity to nutrient enrichment at Black Canyon of the Gunnison NP relative to other national parks is rated as moderate moderate (Sullivan et al. 2011a; Sullivan et al. 2011b). Arid ecosystems are particularly vulnerable to changes caused by nitrogen deposition. Invasive grasses tend to thrive in areas with high nitrogen deposition, displacing native vegetation adapted to low nitrogen conditions. Increases in nitrogen have been found to promote the spread of fast-growing non-native annual grasses (like cheatgrass) and forbs ( like Russian thistle) at the expense of native species (Brooks 2003; Allen et al. 2009; Schwinning et al. 2005). Increased cover of non-native grasses can increase fire risk (Rao et al. 2010). Nitrogen may also increase water use in plants like big sagebrush (Inouye 2006).
Healthy ecosystems can naturally buffer a certain amount of pollution, but as nitrogen and sulfur accumulate, a threshold is passed where the ecosystem is harmed. “Critical load” is a term used to describe the amount of pollution above which harmful changes in sensitive ecosystems occur (Porter 2005). Fortunately, estimated deposition levels at Black Canyon of the Gunnison are low enough that no known critical-loads for park ecosystems are thought to be exceeded.
Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information.
At ground level, ozone is harmful to human health and the environment. Ground-level ozone does not come directly from smokestacks or vehicles, but instead is formed when other pollutants, mainly nitrogen oxides and volatile organic compounds, react in the presence of sunlight.
Over the course of a growing season, ozone can damage plant tissues making it harder for plants to produce and store food. It also weakens plants making them less resistant to disease and insect infestations. A risk assessment that considered ozone exposure, soil moisture, and sensitive plant species concluded that plants in Black Canyon of the Gunnison NP were at low risk of ozone injury (Kohut 2007; Kohut 2004). However, estimated ozone concentrations and cumulative doses at the park are high enough to damage the leaves of sensitive vegetation under certain conditions. The park’s semi-arid conditions cause stomates on plant leaves to close, limiting ozone uptake. At the nearby Rocky Mountain National Park in Colorado, scientists found that in moist areas along streams and seeps, plants may keep stomates open more often, allowing ozone uptake and injury (Kohut et al. 2012). Some plants are more sensitive to ozone than others. Ozone sensitive plants at the park include Amelanchier alnifolia (Saskatoon serviceberry), Populus tremuloides (quaking aspen), and Pinus ponderosa (ponderosa pine) (Binkley et al 1997). Search for more ozone-sensitive plant species found at Black Canyon of the Gunnison NP.
Visit the NPS air quality conditions and trends website for park-specific ozone information.
Allen, E. B., L. E. Rao, R. J. Steers, A. Bytnerowicz, and M. E. Fenn. 2009. Impacts of atmospheric nitrogen deposition on vegetation and soils in Joshua Tree National Park. Pages 78–100 in R. H. Webb, L. F. Fenstermaker, J. S. Heaton, D. L. Hughson, E. V. McDonald, and D. M. Miller, editors. The Mojave Desert: ecosystem processes and sustainability. University of Nevada Press, Las Vegas, Nevada, USA.
Allen, E. B. and L. H. Geiser. 2011. North American Deserts. In L.H. Pardo, M.J. Robin-Abbott and C.T. Driscoll (Eds.). Assessment of Nitrogen Deposition Effects and Empirical Critical Loads of Nitrogen for Ecoregions of the United States. General Technical Report NRS–80. U.S. Forest Service, Newtown Square, PA. pp. 133–142. Available at: http://nrs.fs.fed.us/pubs/38109.
Binkley et al. 1997. Status of Air Quality and Related Values in Class I National Parks and Monuments of the Colorado Plateau. Chapter 5. Black Canyon of the Gunnison National Park. National Park Service, Air Resources Division, Denver, CO. Available at https://irma.nps.gov/DataStore/Reference/Profile/167034.
Brooks, M.L. 2003. Effects of increased soil nitrogen on the dominance of alien annual plants in the Mojave Desert. Journal of Applied Ecology. 40:344–353.
Inouye, R.S. 2006. Effects of shrub removal and nitrogen addition on soil moisture in sagebrush steppe. Journal of Arid Environments. 65: 604–618.
Kohut, B. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the Northern Colorado Plateau Network. Available at https://irma.nps.gov/DataStore/Reference/Profile/2181489.
Kohut R.J. 2007. Ozone Risk Assessment for Vital Signs Monitoring Networks, Appalachian National Scenic Trail, and Natchez Trace National Scenic Trail. NPS/NRPC/ARD/NRTR—2007/001. National Park Service. Fort Collins, Colorado. Available at https://www.nps.gov/articles/ozone-risk-assessment.htm.
Kohut, B., C. Flanagan, E. Porter, J. Cheatham. 2012. Foliar Ozone Injury on Cutleaf Coneflower at Rocky Mountain National Park, Utah. Western North American Naturalist 72(1): 32–42.
Porter, E., Blett, T., Potter, D.U., Huber, C. 2005. Protecting resources on federal lands: Implications of critical loads for atmospheric deposition of nitrogen and sulfur. BioScience 55(7): 603–612. https://doi.org/10.1641/0006-3568(2005)055[0603:PROFLI]2.0.CO;2
Rao, L. E., E. B. Allen, and T. Meixner. 2010. Risk-based determination of critical nitrogen deposition loads for fire spread in southern California deserts. Ecological Applications 20:1320–1335.
Schwinning, S., B. I. Starr, N. J. Wojcik, M. E. Miller, J. E. Ehleringer, R. L. Sanford. 2005. Effects of nitrogen deposition on an arid grassland in the Colorado plateau cold desert. Rangeland Ecology and Management. 58: 565–574.
Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011a. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/313. National Park Service, Denver, Colorado. Available at https://www.nps.gov/articles/nitrogen-risk-assessment.htm
Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011b. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: Northern Colorado Plateau Network (NCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/330. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2168722.
Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011c. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/349. National Park Service, Denver, Colorado. Available at https://www.nps.gov/articles/acidification-risk-assessment.htm.
Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011d. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: Northern Colorado Plateau Network (NCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/366. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170594.
Sullivan, T. J. and T.C. McDonnell. 2014. Mapping of nutrient-nitrogen critical loads for selected national parks in the intermountain west and great lakes regions. Natural Resource Technical Report NPS/ARD/NRTR—2014/895. National Park Service, Fort Collins, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2214130.
Sullivan T.J. 2016. Air quality related values (AQRVs) in national parks: Effects from ozone; visibility reducing particles; and atmospheric deposition of acids, nutrients and toxics. Natural Resource Report. NPS/NRSS/ARD/NRR—2016/1196. National Park Service. Fort Collins, Colorado. Available at https://www.nps.gov/articles/aqrv-assessment.htm.