- Air quality at Mesa Verde National Park
- Related references
Air quality at Mesa Verde National Park
Most visitors expect clean air and clear views in parks. Mesa Verde National Park (NP), Colorado, is well known for the archeological heritage of the Ancestral Pueblo people that it preserves. The park is also affected by air pollution from coal-fired power plants in the Four Corners region, nearby mining, and urban and industrial pollutants from the Southwestern US, California, and Mexico. 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 Mesa Verde NP, and in parks across the U.S., through science, policy and planning, and by doing our part.
Nitrogen and sulfur
Nitrogen and sulfur compounds deposited from the air may have harmful effects, including acidification on soils, lakes, ponds, and streams. Soils and streams in the park generally well-buffered and unlikely to be acidified by atmospheric deposition (Binkley et al. 1997). Still, ecosystems in the park were rated as having high sensitivity to acidification effects relative other national parks (Sullivan et al. 2011c; Sullivan et al. 2011d). Acidification effects can include changes in water and soil chemistry that impact ecosystem health. Some plants are sensitive to acidification, search for acid-sensitive plant species found at Mesa Verde NP.
Excess nitrogen can also lead to nutrient enrichment, a process that changes nutrient cycling and alters plant communities. Ecosystems in the park were rated as having high sensitivity to nutrient-enrichment effects relative to other national parks (Sullivan et al. 2011a; Sullivan et al. 2011b). Non-native grasses thrive in areas with high nitrogen deposition, displacing native vegetation adapted to low nitrogen conditions. Fire risk can subsequently increase due to extensive areas of weedy grasses (Fenn et al. 2003). Wildfires in or near Mesa Verde NP also contribute increased nitrogen to park ecosystems by re-emitting formerly deposited nitrogen from power plants and other sources. Weed density at Mesa Verde NP increases in post-fire environments that tend to support higher soil nitrogen levels (Floyd-Hanna et al. 2004).
Healthy ecosystems can naturally buffer a certain amount of pollution, but as nitrogen accumulates, 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).
Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information. Mesa Verde NP has been monitoring atmospheric nitrogen and sulfur deposition since 1982. Explore air monitoring »
Pollutants like mercury and pesticides are concerning because they are persistent and toxic in the environment. These contaminants can travel in the air thousands of miles away from the source of pollution, even depositing in protected places like national parks. In addition, while some of these harmful pollutants may be banned from use, historically contaminated sites continue to endure negative environmental consequences.
When deposited, airborne mercury and other toxic air contaminants are known to harm wildlife like birds and fish, and cause human health concerns. Many of these substances enter the food chain and accumulate in the tissues of organisms causing reduced reproductive success, impaired growth and development, and decreased survival.
- Mesa Verde experiences high levels of mercury dry deposition, despite the national MATS rule limiting emissions. A study at Mesa Verde showed a statistically significant increase in mercury dry deposition between 2009-2011 (pre-MATS) and 2017-2019 (post-MATS). Evidence suggests that local mercury emissions from nearby cities and oil/gas production areas, as well as large regional wildfires, notably contribute to dry deposition of mercury at Mesa Verde NP (Sather et al. 2021).
- Mercury concentrations in fish sampled at Mesa Verde did not exceed any known toxicity thresholds for fish or birds. Speckled dace (prey fish) were sampled and analyzed for mercury from one site at the park and compared to data across 21 western parks. The average fish mercury concentration (74.9 ng/g ww) was slightly lower than the study-wide mean (77.7 ng/g ww). However, the data may not reflect the risk at other unsampled locations in the park (Eagles-Smith et al. 2014).
- Related studies found mercury in fish exceeding wildlife and human health consumption thresholds (Peterson et al. 2007; CDPHE 2009) and elevated levels of mercury in lake sediments and zooplankton (Nydick 2010). However, a pilot study of mercury in park biota did not find elevated mercury levels in songbirds, invertebrates, stream fish, or crayfish (Nydick and Williams 2010).
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. The risk of injury to plants is generally low in the park (Kohut 2004) partly because in arid areas plants close leaf stomata to limit moisture loss, which also limits ozone uptake. No signs of ozone damage to plant leaves have been reported in or near to the park (Binkley et al. 1997; Nydick 2009). Some plants are more sensitive to ozone than others. Ozone-sensitive plant species in Mesa Verde NP include Populus tremuloides (quaking aspen), Apocynum androsaemifolium (spreading dogbane), and Rhus trilobata (skunkbush). Search for more ozone-sensitive plant species found at Mesa Verde NP.
Visit the NPS air quality conditions and trends website for park-specific ozone information. Mesa Verde NP has been monitoring ozone since 1993. View live ozone and meteorology data, and explore air monitoring »
Visitors come to Mesa Verde NP to enjoy a spectacular look into the lives of the park’s early inhabitants, the Ancestral Puebloans who made it their home from the years 600 to 1300. Unimpaired visibility has special importance at Mesa Verde NP from a historical context. The Ancestral Puebloans were highly dependent on visual contact for long-distance communication. Preserving clear views is critical for understanding of this culture and sharing the experience of distant viewing with current and future generations.
Unfortunately, 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, and dust reduce visibility as well. Mesa Verde NP participates in a multi-agency dust monitoring network spread across the Colorado plateau. A special sampler collects airborne particles, while a live webcam records dust storms in the area. Large dust deposition events that reduce visibility and cause restrictions in air traffic have occurred. Dust deposited on snow can also cause the early onset of snowmelt reducing spring runoff.
Significant improvements in park visibility on the clearest days have been documented since the 1990’s. Overall, visibility in the park still needs improvement to reach the Clean Air Act goal of no human caused impairment.
- Reduced visibility sometimes due to human-caused haze and fine particles of air pollution, including dust;
- Reduction of the average natural visual range from about 175 miles (without the effects of pollution) to about 130 miles because of pollution at the park;
- Reduction of the visual range to below 90 miles on high pollution days.
Visit the NPS air quality conditions and trends website for park-specific visibility information. Mesa Verde NP has been monitoring visibility since 1989. View live webcams and explore air monitoring »
Binkley, D., Giardina, C., Dockersmith, I., Morse, D., Scruggs, M., Tonnessen, K. 1997. Status of Air Quality and Related Values in Class I National Parks and Monuments of the Colorado Plateau. National Park Service, Air Resources Division, Denver, Colorado. Chapter 11: Mesa Verde National Park. Available at https://irma.nps.gov/DataStore/Reference/Profile/167034.
Caldwell, C. A., Swartzendruber, P. Prestbo, E. 2006. Concentration and dry deposition of mercury species in arid south central New Mexico (2001–2002). Environ. Sci. Technol. 40: 7535–7540.
[CDPHE] Colorado Department of Public Health and Environment. 2009. Colorado Fish Tissue Study. Available at https://www.colorado.gov/cdphe/wq-fish-consumption.
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
Fenn, M. E., Haeuber, R., Tonnesen, G. S., Baron, J. S., Grossman-Clarke, S., Hope, D., Jaffe, D. A., Copeland, S., Geiser, L., Rueth, H. M., and Sickman, J. O. 2003. Nitrogen emissions, deposition and monitoring in the western United States. Bioscience 53: 391–403.
Floyd-Hanna, L., Hanna, D., Romme, W. H., Crews, T. 2004. Non-native invasions following fire in Southwestern Colorado: Long-term effectiveness of mitigation treatments and future predictions. Joint Fire Science Program, product number 1496-BLM2-454.
Four Corners Air Quality Task Force. 2007. Four Corners Air Quality Task Force Report of Mitigation Options. Available at https://www.env.nm.gov/air-quality/fcaqg/.
Kohut, R. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the Southern Colorado Plateau Network. Available at https://irma.nps.gov/DataStore/Reference/Profile/2181544
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
[NADP] National Atmospheric Deposition Program. 2010. National Atmospheric Deposition Program 2009 Annual Summary. NADP Data Report 2010-01. Illinois State Water Survey, University of Illinois at Urbana-Champaign, IL.
[NPS] National Park Service. 2010. Air Quality in National Parks: 2009 Annual Performance and Progress Report. Natural Resource Report NPS/NRPC/ARD/NRR—2010/266. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/662783.
Nydick, K. 2009. Assessment of Foliar Ozone Injury: Pilot Project. A Report to the San Juan Public Lands Center (USFS/BLM). Mountain Studies Institute, San Juan Mountains, Colorado.
Nydick, K. 2010. Mercury in Precipitation and Lakes of Southwestern Colorado. Mountain Studies Institute Report 2010-02.
Nydick, K. and Williams, K. 2010. Final Report: Pilot Study of the Ecological Effects of Mercury Deposition in Mesa Verde National Park, Colorado. Mountain Studies Institute Report 2010-01.
Peterson, S. A., Van Sickle, J., Herlihy, A. T., and Hughes, R. M. 2007. Mercury Concentration in Fish from Streams and Rivers throughout the Western United States. Environ. Sci. Technol. 41: 58–65.
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
Sather, Mark E., Shaibal Mukerjee, Luther Smith, Johnson Mathew, Clarence Jackson, Michael Flournoy. 2021. Gaseous Oxidized mercury dry deposition measurements in the Four Corners area, U.S.A., after large power plant mercury emission reductions. Atmospheric Pollution Research 12(1): 148-158. https://doi.org/10.1016/j.apr.2020.08.030
Sather, M., Mukerjee, S., Landis, M., Mathew, J., Brunette, B., Karlstrom, J., Van der Jagt, G., Lewis, N., Faverman, J. 2010. Passive Monitoring of Ambient Reactive Gaseous Mercury in the Four Corners Area and Eastern Oklahoma. Presented at the 2010 NADP Annual Meeting and Scientific Symposium, Lake Tahoe, CA, October 21, 2010.
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: Southern Colorado Plateau Network (SCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/330. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2168742.
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. 2011c. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: Southern Colorado Plateau Network (SCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/349. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170600.
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.