Series: Park Air Profiles

Park Air Profiles - Rocky Mountain National Park

Hallett Peak reflected in the water of Dream Lake in Rocky Mountain NP
Visitors come to Rocky Mountain NP to enjoy scenic views of alpine lakes, forests, and wildlife in the Rocky Mountains.

Air quality at Rocky Mountain National Park

Most visitors expect clean air and clear views in parks. Rocky Mountain National Park (NP), Colorado, is impacted by many sources of air pollution, including vehicles, power plants, agriculture, fire, oil and gas, and other industry. 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 Rocky Mountain NP, and in parks across the U.S., through science, policy and planning, and by doing our part.

Nitrogen and sulfur

Excess nitrogen and sulfur compounds deposited from the air may have harmful effects, including nutrient imbalances and loss of biodiversity in high elevation lakes, forests, and alpine plant communities in the park. Three-quarters of the park is above 9,000 feet in elevation. These high elevation ecosystems are particularly vulnerable to nitrogen deposition. These systems receive more nitrogen deposition than lower elevation areas because of greater amounts of snow and rain, and short growing seasons and shallow soils limit the capacity of soils and plants to absorb nitrogen.

Long-term research in Rocky Mountain NP has found that, over time, increasing nitrogen deposition has caused changes in soils, alpine tundra plant communities, spruce forests, and alpine lakes (Baron 2006; Rueth et al. 2002). The earliest of these documented changes began in the 1950s, when nitrogen deposition from rain and snow was about 1.5 kilograms per hectare per year; the “critical load” according to scientists. “Critical load” is a term used to describe the amount of pollution above which harmful changes in sensitive ecosystems occur (Porter 2005). Reducing nitrogen deposition to below the critical load is a park resource management goal, and is a goal for the Rocky Mountain NP Initiative to protect and restore natural resources at the park (Porter and Johnson 2007).

Nitrogen effects

  • Nitrogen saturation of soils in high-elevation watersheds. Excess nitrogen leaks from the soils into lakes and streams, altering water chemistry (Baron et al. 2000).
  • Alteration of aquatic communities in alpine lakes, with changes in the amounts and types of microscopic organisms called diatoms (Wolfe et al. 2001).
  • Stimulation of soil microbial activity, resulting in increased mineralization and nitrification, processes that create more available nitrogen; and elevated nitrogen in spruce needles, potentially causing greater susceptibility to forest disease, drought, or insect infestations (Rueth et al. 2002).
  • Excess fertilization of alpine plant communities, placing them at the threshold of shifting from forbs—such as showy wildflowers—to increased grasses (Bowman et al. 2014).
  • Increased nitrogen concentrations in lichens, organisms that grow on trees and rocks (RMNP Initiative 2012).
  • Nitrogen deposition exceeds the critical load for one or more park ecosystems (NPS ARD 2018).

Nitrogen, together with sulfur, can also acidify surface waters and soils. Ecosystems at Rocky Mountain NP are very highly sensitive to acidification relative to other national parks (Sullivan et al. 2011c; Sullivan et al. 2011d). Some plants are sensitive to acidification, search for acid-sensitive plant species found at Rocky Mountain NP.

Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information. Rocky Mountain NP has been monitoring nitrogen and sulfur deposition since 1980. Explore air monitoring data »

Citizen scientists and a park ranger collecting dragonfly larvae in Rocky Mountain NP
A park ranger and citizen scientists participate in the Dragonfly Mercury Project in Rocky Mountain NP.
Mercury and toxics

Airborne mercury, and other toxic air contaminants, when deposited are known to harm birds, salamanders, fish and other wildlife, and cause human health concerns. These substances enter the food chain and accumulate in the tissue of organisms causing reduced reproductive success, impaired growth and development, and decreased survival.

Mercury and toxics effects:

  • Pesticide and mercury concentrations in some fish from Rocky Mountain NP exceed human and/or wildlife health thresholds (Eagles-Smith et al. 2014; Flanagan Pritz et al. 2014; Landers et al. 2008; Landers et al. 2010)
  • Current-use pesticides (chlorpyrifos, dacthal, endosulfans) are particularly high in fish from parks in the Rockies (including Rocky Mountain NP) and Sierra Nevada, as compared to levels found in fish from parks in Alaska and the Cascades (Flanagan Pritz et al 2014).
  • Agricultural and industrial contaminants (e.g., flame retardants, PBDEs) have been detected in fish and sediment. Lake sediment records indicate that PBDEs are increasing rapidly in park ecosystems (Landers et al. 2008; Landers et al. 2010).
  • Elevated concentrations of mercury in snow, rain, and sediment compared to other western U.S. national parks (Landers et al. 2008; Landers et al. 2010).
  • Contaminants are generally higher on the park’s east side compared to the west side (Landers et al. 2008; Landers et al. 2010).
  • Male intersex fish (the presence of both male and female reproductive structures in the same fish) found in the park, which often indicates exposure to contaminants (Landers et al. 2008; Schreck and Kent 2013).
  • Dragonfly larvae collected by citizen scientists from some sites at the park have elevated mercury levels (Nelson et al. 2015; Eagles-Smith et al. 2016).

Ground-level ozone

Park rangers working on an ozone garden in Rocky Mountain NP. Rocky Mountain NP uses gardens of ozone-sensitive plants to educate park visitors on the harmful effects of ground-level ozone.

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.

Especially during the summer months, ozone levels in the park sometimes exceed the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health. Ozone is a respiratory irritant, causing coughing, sinus inflammation, chest pains, scratchy throat, lung damage, and reduced immune system functions. Children, the elderly, people with existing health problems, and active adults are most vulnerable. When ozone levels exceed, or are predicted to exceed, health standards, Rocky Mountain NP staff post health advisories cautioning staff and visitors of the potential health risks associated with exposures to elevated levels.

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. There are at least 15 ozone-sensitive plants in the park, including: cutleaf coneflowers (Rudbeckia laciniata), quaking aspen (Populus tremuloides), Scouler’s willow (Salix scouleriana), white sagebrush (Artemisia ludoviciana), and Canadian goldenrod (Solidago canadensis). Surveys at the park, reveal visible injury to cut-leaf coneflower leaves (Kohut 2012). Search ozone-sensitive plant species found at Rocky Mountain NP.

Visit the NPS air quality conditions and trends website for park-specific ozone information. Rocky Mountain NP has been monitoring ozone since 1987. Explore air monitoring data »

Visibility

Bierstadt Lake in Rocky Mountain NP Clean, clear air is essential to appreciating the scenic vistas at Rocky Mountain NP.

Park vistas are sometimes obscured by haze, reducing 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 park visibility have been documented since the 1990’s. Still, visibility in the park needs improvement to reach the Clean Air Act goal of no human caused impairment.

Visibility effects:
  • Reduction of the average natural visual range from about 175 miles (without the effects of pollution) to about 135 miles because of pollution at the park.
  • Reduction of the visual range in the summer from about 120 miles to below 75 miles on high pollution days.

Explore scenic vistas through three live webcams at Rocky Mountain National Park!

Visit the NPS air quality conditions and trends website for park-specific visibility information. Rocky Mountain NP has been monitoring visibility since 1979. Explore air monitoring »

Baron, J.S., Rueth, H.M., Wolfe, A.N., Nydick, K.R., Allstott, E.J., Minear, J.T., Moraska, B. 2000. Ecosystem responses to nitrogen deposition in the Colorado Front Range. Ecosystems 3: 352–368.

Baron, J.S. 2006. Hindcasting Nitrogen Deposition to Determine an Ecological Critical Load. Ecological Applications 16(2): 433–439.

Bowman, W.D., Gartner, J.R., Holland, K., Wiedermann, M. 2006. Nitrogen Critical Loads for Alpine Vegetation and Terrestrial Ecosystem Response: Are We There Yet? Ecological Applications 16(3): 1183–1193.

Eagles-Smith, C.A., Nelson, S.J., Willacker, J.J., Jr., Flanagan Pritz, C.M., and Krabbbenhoft, D.P., 2016, Dragonfly Mercury Project—A citizen science driven approach to linking surface-water chemistry and landscape characteristics to biosentinels on a national scale: U.S. Geological Survey Fact Sheet 2016-3005, 4 p., http://dx.doi.org/10.3133/fs20163005.

Eagles-Smith, C.A., J.J. Willacker, and C.M.Flanagan Pritz. 2014. Mercury in fishes from 21 national parks in the Western United States—Inter and intra-park variation in concentrations and ecological risk: U.S. Geological Survey Open-File Report 2014-1051, 54 p. Available at: http://dx.doi.org/10.3133/ofr20141051.

Flanagan Pritz, C. M., J. E. Schrlau, S. L. Massey Simonich, T. F. Blett. 2014. Contaminants of Emerging Concern in Fish from Western U.S. and Alaskan National Parks – Spatial Distribution and Health Thresholds. Journal of American Water Resources Association 50 (2): 309–323. Available at https://irma.nps.gov/App/Reference/Profile/2210538.

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, R., C. Flanagan, E. Porter, J. Cheatham. 2012. Foliar Ozone Injury on Cutleaf Coneflower at Rocky Mountain National Park, Colorado. Western North American Naturalist 72(1): 32–42. . Available at https://irma.nps.gov/DataStore/Reference/Profile/2187617.

Landers, D.H., Simonich, S.M., Jaffe, D.A., Geiser L.H., Campbell, D.H., Schwindt, A.R., Schreck, C.B., Kent, M.L., Hafner, W.D., Taylor, H.E., Hageman, K.J., Usenko, S., Ackerman, L.K., Schrlau, J.E., Rose, N.L., Blett, T.F., and Erway, M.M. 2008. The Fate, Transport, and Ecological Impacts of Airborne Contaminants in Western National Parks (USA). EPA/600/R-07/138. U.S. Environmental Protection Agency, Office of Research and Development, NHEERL, Western Ecology Division, Corvallis, Oregon. Available at https://irma.nps.gov/DataStore/Reference/Profile/660829

Landers, D.H., Simonich, S.M., Jaffe, D.A., Geiser L.H., Campbell, D.H., Schwindt, A.R., Schreck, C.B., Kent, M.L., Hafner, W.D., Taylor, H.E., Hageman, K.J., Usenko, S., Ackerman, L.K., Schrlau, J.E., Rose, N.L., Blett, T.F., and Erway, M.M. 2010. The Western Airborne Contaminant Assessment Project (WACAP): An Interdisciplinary Evaluation of the Impacts of Airborne Contaminants in Western U.S. National Parks. Environmental Science and Technology. Vol 44: 855–859.

Nelson, S. J., H. M. Webber, and C. M. Flanagan Pritz. 2015. Citizen scientists study mercury in dragonfly larvae: Dragonfly larvae provide baseline data to evaluate mercury in parks nationwide. Natural Resource Report NPS/NRSS/ARD/NRR—2015/938. National Park Service, Fort Collins, Colorado

[NPS] National Park Service. 2004. Nitrogen Deposition: Issues and Effects in Rocky Mountain National Park. Technical Background Document.

NPSpecies, Information of Species in National Parks. “Rocky Mountain National Park (ROMO).” IRMA Portal version. National Park Service. Accessed June 6, 2018. Available at https://irma.nps.gov/NPSpecies/Reports/Systemwide/Ozone-sensitive%20Species%20in%20a%20Park.

Pardo, L.D., M.J. Robin-Abbott, C.T. Driscoll, eds. 2011. Assessment of nitrogen deposition effects and empirical critical loads of nitrogen for ecoregions of the United States. Gen. Tech. Rep. NRS-80. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. Available at: http://www.nrs.fs.fed.us/pubs/38109.

Porter, E. and Johnson, S. 2007. Translating science into policy: Using ecosystem thresholds to protect resources in Rocky Mountain National Park. Environmental Pollution 149: 268–280.

Rueth, H.M. and Baron, J.S. 2002. Differences in Englemann spruce forest biogeochemistry east and west of the Continental Divide in Colorado, USA. Ecosystems 5:45–57.

Schreck, C.B. and M. Kent. 2013. Extent of Endocrine Disruption in Fish of Western and Alaskan National Parks. NPS-OSU Task Agreement J8W07080024. NPS Final Report, 72 pp.

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: Rocky Mountain Network (ROMN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/313. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2168730

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., McDonnell, T. C., McPherson, G. T., 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: Rocky Mountain Network (ROMN). Natural Resource Report. NPS/NRPC/ARD/NRR—2011/371. National Park Service, Natural Resource Program Center. Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170599

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

Wolfe, A.P., Baron, J. S., Cornett, J.S. 2001. Anthropogenic nitrogen deposition induces rapid ecological changes in alpine lakes of the Colorado Front Range (USA). Journal of Paleolimnology 25: 1–7.

Last updated: June 27, 2018