Air Pollution Impacts

Many visitors come to Point Reyes NS to enjoy views of this narrow, steep-ridged peninsula, “a portion of the diminishing seashore of the U.S. that remains undeveloped.” While natural fog forms over the ocean, blanketing the seashore and obscuring spectacular vistas, occasionally the vistas are obscured by human-caused haze from the San Francisco Bay Area. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze and visibility impairment. Organic compounds, soot, and dust reduce visibility as well.

Visibility effects at Point Reyes NS include:

• Reduced visibility on some days due to human-caused haze and fine particles of air pollution;
• Reduction of the average natural visual range from about 80 miles (without the effects of pollution) to about 40 miles because of pollution at the park;
• Reduction of the visual range from about 50 miles to below 20 miles on high pollution days.

(Source: IMPROVE 2010)

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Nitrogen and sulfur compounds deposited from air pollution can harm surface waters, soils, and vegetation. The arid and semi-arid ecosystems in Point Reyes NS are particularly vulnerable to changes caused by nitrogen deposition. Although atmospheric nitrogen inputs are relatively low in the area, nitrogen loading can disrupt soil nutrient cycling and alter plant communities (Sullivan et al. 2001 [pdf, 6.3 KB]). In other areas of California, nitrogen deposition appears to play an important role in the ongoing replacement of native plant species with exotic, invasive annuals in coastal sage scrub communities (Fenn et al. 2003). Native plants that have evolved under nitrogen-poor conditions are replaced by invasive species that are able to take advantage of increased nitrogen levels.

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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 and seasonal exposures are generally low at Point Reyes NS and unlikely to cause plant injury or reduced growth (Sullivan et al. 2001 [pdf, 6.3 KB]). However, several park species, including Artemisia douglasiana (Douglas’ sagewort) and Sambucus mexicana (blue elderberry), are known to be sensitive to ozone.

Search the list of ozone-sensitive plant species (pdf, 184 KB) found at each national park.

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Toxic air pollutants include pesticides, industrial by-products, heavy metals like mercury, and flame retardants for fabrics. Lichens, a group of non-vascular plants that accumulate such contaminants and are sensitive to airborne pollutants, can be used as indicators of urban pollution and point-source emissions like power plants.

Elevated mercury concentrations have been found in lichens from the seashore at high elevation sites that intercept fog. Additionally, concentrations of arsenic and lead decrease with distance from south to north at the seashore, suggesting these two elements originate in the fine particulate haze that enters the park from San Francisco Bay Area (Bennett and Benson 2005).

Once such toxic contaminants enter the food chain, effects in wildlife and humans can include reproductive problems, impaired growth and development, behavioral abnormalities, reduced immune response, chronic illness, cancer, and death.

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