Air quality at Bryce Canyon National Park
Most visitors expect clean air and clear views in parks. Bryce Canyon National Park (NP), Utah, is home to the largest concentration of hoodoos—totem-shaped rock spires resistant to erosion—in the world. The park enjoys relatively good air quality given its remote location on the Colorado Plateau. However, upwind urban and industrial sources, including large power plants and mines, can harm the park’s natural and scenic resources such as vegetation, surface waters, and visibility. The National Park Service works to address air pollution effects at Bryce Canyon NP, and in parks across the U.S., through science, policy and planning, and by doing our part.
Visitors come to Bryce Canyon NP to experience the spectacular terrain of the Bryce Amphitheater against the forests and meadows of the Paunsaugunt Plateau, and the spectacular night sky. Park vistas, while usually quite clear, 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.
Smoke from wildfires often affects visibility on the haziest days. At night, pollution can make stargazing more difficult because it scatters artificial light — increasing the impact of light pollution. Significant improvement in park visibility on the clearest days has been documented since the 1990’s, but visibility on the haziest days has not changed significantly. Overall, visibility in the park still needs improvement to reach the Clean Air Act goal of no human caused impairment.
- Reduction of the average natural visual range from about 175 miles (without pollution) to about 140 miles because of pollution at the park
- Reduction of the visual range to below 95 miles on high pollution days
Visit the NPS air quality conditions and trends website for park-specific visibility information. Bryce Canyon NP has been monitoring visibility since 1988. Check out the live air quality webcam and explore air monitoring »
Nitrogen and sulfur
Nitrogen and sulfur compounds deposited from the air may have harmful effects, including nutrient imbalances and loss of biodiversity. 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). Nitrogen deposition exceeds the critical load for one or more park ecosystems (NPS ARD 2018). Ammonium, a species of nitrogen that often indicates nearby agricultural sources, has been increasing in wet deposition at the park (Lehmann et al. 2007).
Nitrogen, together with sulfur, can also acidify surface waters and soils. Given the abundance of base cations in park soils and rocks, surface waters in Bryce Canyon NP are generally well-buffered from acidification. However, the park’s seeps and springs may be sensitive to acid inputs. Additionally, small streams with steep-sided canyon walls in the park have little ability to retain nutrients and water, hindering their ability to buffer potentially acidic run-off. The ecosystem sensitivity to acidification from nitrogen and sulfur at Bryce Canyon NP relative to other national parks is high (Sullivan et al. 2011c; Sullivan et al. 2011d). Some plants are sensitive to acidification, search for acid-sensitive plant species found at Bryce Canyon NP.
Although nitrogen is necessary for plants to grow, too much nitrogen can lead to nutrient enrichment, a process that disrupts the balance of plant communities, promoting the growth and spread of fast-growing invasive grasses (e.g., cheatgrass) and forbs (e.g., Russian thistle) at the expense of native species (Brooks 2003; Schwinning et al. 2005; Allen et al. 2009). Plants in arid shrubland and grassland ecosystems are particularly vulnerable to changes caused by nitrogen deposition. Widespread invasive grasses can increase fire risk (Rao et al. 2010; Balch et al. 2013) and affect plant biodiversity. A study rated ecosystems at Bryce Canyon NP as low sensitivity for nutrient enrichment from nitrogen deposition relative to other national parks (Sullivan et al. 2011a; Sullivan et al. 2011b). Excess nitrogen may also increase water use in plants like big sagebrush (Inouye 2006).
Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information. Bryce Canyon NP has been monitoring nitrogen and sulfur deposition since 1985, explore air monitoring »
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 the leaves of plants, reducing their growth rate and making them less resistant to disease and insect infestations. An ozone risk assessment concluded that plants in Bryce Canyon NP were at low risk of foliar ozone injury (Kohut 2004). However, estimated ozone concentrations and cumulative doses at the park are high enough to induce foliar injury to sensitive vegetation under certain conditions.
Generally, dry conditions in the park during peak ozone concentrations are likely to limit ozone uptake by plants. However along streams and seeps, where conditions are wetter, plants may have higher ozone uptake and injury (Kohut et al. 2012). Ozone sensitive plants at the park include Apocynum cannabinum (common dogbane) and Populus tremuloides (quaking aspen). Past surveys at the park found probable ozone injury on Sambucus caerulea (blue elderberry) (NPS 2000). Some plants are more sensitive to ozone than others. Search ozone-sensitive plant species found at Bryce Canyon 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 6. Bryce Canyon National Park. National Park Service, Air Resources Division, Denver, CO. Available at https://irma.nps.gov/DataStore/Reference/Profile/167034.
Bowman, W. D., J. S. Baron, L. H. Geiser, M. E. Fenn, E. A. Lilleskov. 2011. Northwestern Forested Mountains. 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.
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.
Lehmann, C. M. B., V. C. Bowersox, R. S. Larson, S. M. Larson. 2007. Monitoring Long-term Trends in Sulfate and Ammonium in US Precipitation: Results from the National Atmospheric Deposition Program/National Trends Network. Acid Rain-Deposition to Recovery: 59–66. Water Air Soil Pollution: Focus.
[NPS] National Park Service. 2000. Results of 1999 ozone injury surveys at Bryce Canyon NP, Cedar Breaks NM and Zion NP. Memorandum. Available at https://irma.nps.gov/App/Reference/Profile/581126.
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 Utah 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—2011/313. 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, Utah. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170594.
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.