For more information about National Park Service air resources, please visit http://www.nature.nps.gov/air/.
Air Pollution Impacts
Redwood National Park
Natural and scenic resources in Redwood National Park (NP) are susceptible to the harmful effects of air pollution. Fine particles, nitrogen, and ozone impact natural resources such as vegetation and surface waters, 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 Redwood NP.
- Visibility
- Nitrogen & Sulfur
- Ozone
Many visitors come to Redwood NP to enjoy views of primeval redwood forests against the rugged coastline of the Pacific Ocean. Unfortunately, this scene is 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 haze and visibility impairment. Additionally, organic compounds, soot, dust, and wood smoke reduce visibility. Naturally-occurring marine fog, which also impairs visibility at the park, provides necessary water to the moisture-loving redwood needles.
Visibility effects at Redwood NP include:
- Reduced visibility, at times, due to human-caused haze and fine particles of air pollution;
- Reduction of the average natural visual range from about 100 miles (without the effects of pollution) to about 65 miles because of pollution at the park;
- Reduction of the visual range to below 40 miles on high pollution days.
(Source: IMPROVE 2010)
Nitrogen (N) and sulfur (S) compounds deposited from air pollution can harm surface waters, soils, and vegetation. Atmospheric N and S inputs are relatively low at Redwood NP, and the park’s well-buffered streams and well-developed soils are relatively insensitive to acidification from N and S (Sullivan et al. 2011c; Sullivan et al. 2011d [pdf, 2.6 MB]). However, while Redwood NP trees and streams are not particularly sensitive to N enrichment (Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 6.8 MB]), some species of forest lichens are very sensitive, and may decrease in abundance as nitrogen increases (Fenn et al. 2010).
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 forest lichen communities, with sensitive species gradually replaced by pollution-tolerant species. The amount of nitrogen that ecosystems can tolerate without significant harm is called the critical load. Critical loads can be used to establish air quality goals for ecosystem protection and management. In California, the critical load for sensitive forest lichen species is about 3.1 kg N/ha/yr (Fenn et al. 2010). N deposition in the area is relatively low (estimated at less than 1 kg/ha/yr), but if development increased in the region, emissions of nitrogen oxides and other pollutants would increase deposition at the park and subsequent risk to forests, lakes, and streams.
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.
An ozone monitor from 1987–1995 at Redwood NP reported low ozone concentrations compared to other California parks (Sullivan et al. 2001 [pdf, 6.3 MB]). However, there are a few ozone-sensitive plants in Redwood NP including Pinus jeffreyi (Jeffrey pine), Alnus rubra (red alder), and Artemisia douglasiana (Douglas’ sagewort). A risk assessment that considered ozone exposure, soil moisture, and sensitive plant species concluded that plants in Redwood NP were at moderate risk of foliar ozone injury (Kohut 2004 [pdf, 120 KB]). The USDA Forest Service did not find ozone injury on trees examined near the park (specifically, in the northern end of the North Coast air basin) (Campbell et al. 2007 [pdf, 2.3 MB]). However, that survey did not look at understory plants.
Search the list of ozone-sensitive plant species (pdf, 184 KB) found at each national park.
Featured Content
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 Redwood NP.
Related Links
Last Updated: January 13, 2012
