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Air Pollution Impacts
Pinnacles National Park
Natural and scenic resources in Pinnacles National Park (NP) are susceptible to the harmful effects of air pollution. Nitrogen, ozone, mercury, and fine particles impact natural resources such as surface waters and vegetation, and scenic resources such as visibility. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Pinnacles NP.
- Nitrogen & Sulfur
Visitors come to Pinnacles NP to enjoy spectacular views of the namesake rock pinnacles, chaparral-covered Gabilan Mountains, and talus passages. Unfortunately, park vistas are sometimes obscured by haze caused by fine particles in the air. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze and visibility impairment. Additionally, organic compounds, soot, and dust reduce visibility. Smoke from nearby forest or chaparral fires also contribute to particulate matter in the region.
Visibility effects at Pinnacles NP include:
- Reduced visibility, at times, due to human-caused haze from fine particles of air pollution;
- Reduction of the average natural visual range from about 140 miles (without pollution) to about 60 miles because of pollution at the park;
- Reduction of the visual range to below 35 miles on high pollution days.
(Source: IMPROVE 2010)
Nitrogen (N) and sulfur (S) compounds deposited from air pollution can harm soils and vegetation at Pinnacles NP. While N and S deposition is relatively low, N deposition may disrupt soil nutrient cycling and alter plant communities. In other areas of California, increased N deposition has allowed weedy annual grasses to invade shrublands, grasslands, and coastal chaparral communities, similar to those present at Pinnacles NP (Fenn et al. 2003). These grasses have replaced native plants that evolved under N-poor conditions. The monument is highly sensitive to N-enrichment effects (Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 5.9 MB]). At Joshua Tree NP in southern California, increased N deposition has contributed to invasions of annual grasses and increased fire risk in shrublands (Rao et al. 2010).
The monument’s physical characteristics, including steep-sided watersheds and the presence of very small uppermost streams (i.e. low-order), are typically associated with high acid sensitivity (Sullivan et al. 2011c; Sullivan et al. 2011d [pdf, 2.1 MB]). However, site-specific data indicate that sensitivity to acidification at the monument is low due to high availability of base cations in soils and streams to buffer acid deposition (Sullivan et al. 2001 [pdf, 6.3 KB]).
How much nitrogen is too much?
Nitrogen is a fertilizer and some nitrogen is necessary for plants to grow. However, in natural ecosystems, too much nitrogen can disrupt the balance of plant communities, allowing weedy species to grow faster. For example, too much nitrogen causes changes in lichen communities, with sensitive species gradually replaced by pollution-tolerant species. The amount of nitrogen that ecosystems (e.g., lichen communities) can tolerate without significant harm is called the critical load. In California, the critical load for sensitive lichen species is about 3.1 kilogram N per hectare per year (kg/ha/yr) (Fenn et al. 2010). N deposition can also promote invasive species like cheatgrass, which could be a problem in grasslands like those in Pinnacles NP (Vasquez et al. 2008). Wet N deposition in the area is relatively low (less than 0.5 kg/ha/yr), but total N deposition may be as high as 5–10 kg/ha/yr (Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 5.9 MB]). Pinnacles NP contains an abundant lichen community, which give the namesake pinnacle rocks their varied hues. Many of the species present are known to be sensitive to air pollution; N and (S) species have been detected in lichens sampled at the monument (Jovan 2008 [pdf, 4.5 MB]; Jovan and McCune 2005 [pdf, 334 KB]. Critical loads can be used to establish air quality goals for ecosystem protection and management.
Naturally-occurring ozone in the upper atmosphere absorbs the sun’s harmful ultraviolet rays and helps to protect all life on earth. However, in the lower atmosphere, ozone is an air pollutant, forming when nitrogen oxides from vehicles, power plants, and other sources combine with volatile organic compounds from gasoline, solvents, and vegetation in the presence of sunlight. In addition to causing respiratory problems in people, ozone can injure plants. Ozone enters leaves through pores (stomata), where it can kill plant tissues, causing visible injury, or reduce photosynthesis, growth, and reproduction.
Ozone concentrations at Pinnacles NP are elevated (NPS 2010 [pdf, 2.8 MB]) and sometimes exceed levels known to harm sensitive vegetation. Pinnacles NP contains ozone-sensitive plants including Artemisia douglasiana (mugwort), Sambucus mexicana (blue elderberry), and Apocynum cannabinum (Indian hemp). A risk assessment that considered ozone exposure, soil moisture, and sensitive plant species concluded that plants in Pinnacles NP were at high risk of foliar ozone injury (Sullivan et al. 2001 [pdf, 6.3 MB]; Kohut 2004 [pdf, 137 KB]), however surveys to evaluate injury have not been conducted in the park. The USDA Forest Service surveyed two forested sites near the Monument (North Central Coast air basin), finding a high level of injury at one site but no injury at the other site (Campbell et al. 2007 [pdf, 2.3 MB]).
Search the list of ozone-sensitive plant species (pdf, 184 KB) found at each national park.
Studies and monitoring help the NPS understand the environmental impacts of air pollution. Access air quality data and see what is happening with Studies and Monitoring at Pinnacles NP.
Last Updated: February 03, 2016