California’s Smog Problem Spreads to National Parks

Trees as far north as Yosemite National Park are feeling the scourge of smog, and hikers at Sequoia and Kings Canyon national parks may soon be warned when the air there is unhealthful to breathe, according to park officials.

The pollution is troubling not only because it is harming some of the nation’s most scenic wilderness preserves but also because it threatens to become substantially worse. The smog comes primarily from the rapidly developing San Joaquin Valley, where weather and geography combine to give it the potential of one day outranking Los Angeles in smog.

Ozone, the most prevalent and most hazardous component of smog, is ravaging trees both in Yosemite and Sequoia parks. Researchers say the pollution weakens trees and makes them more susceptible to the effects of drought and pests. Although smog damage has been well-documented in Southern California forests, researchers are only now studying the mechanism by which it contributes to tree mortality in the Sierra Nevada.

Diane Ewell, air-quality specialist at Sequoia, said ozone levels exceed state health standards an average of 46 days each summer at lower elevations in Sequoia and Kings Canyon and an average of 16 days at the higher elevations.

Medical evidence shows that smog at these levels is harmful to sensitive individuals, including children, the elderly and people with lung or heart ailments. Ozone damages the tissues of the lungs and can cause shortness of breath.

Ewell estimated that 10% to 20% of the parks’ cone-bearing trees are dead--weakened by smog and drought and finished off by a stubborn infestation of bark beetles.

“You can just see the dead trees on the road--the green mixed in with the brown,� Ewell said. “It’s very apparent.�

Smog levels at Sequoia exceeded higher federal ozone standards for two days in 1987 and 10 days in 1982, she said. To warn visitors, Sequoia plans to post advisories describing smog conditions as good, moderate or unhealthful. Unhealthful conditions will include times when the smog exceeds the federal standards.

“We are thinking about doing a number of things, putting up roadside signs, site bulletins at the visitor center and on letter boards� where campground information is posted, she said.

Despite the pollution, hikers at Sequoia and Kings Canyon do not complain about smog. Ozone is invisible, and many hikers confuse its effects, such as shortness of breath, with the effects of higher elevations, Ewell said.

Smog levels tend to be lower in Yosemite than in Sequoia and Kings Canyon. “Yosemite is farther away from the source, and we are in the foothills and more exposed,� Ewell said.

Joan McLaughlin, Yosemite’s air-quality monitoring specialist, said smog exceeds state health standards in parts of the park for several days each summer, but the levels have not surpassed federal standards since the summer of 1987, when there were three days of particularly high ozone. McLaughlin said Yosemite has no plans to issue smog alerts to visitors.

Although unhealthful, air pollution in the Sierra Nevada is still substantially below the levels reached in Los Angeles during first-stage smog alerts. By the time a smog alert is declared in Los Angeles, the pollution is more than double what the state considers to be unhealthful for sensitive individuals.

During first-stage alerts, the air is considered “very unhealthful.� Children, the elderly and individuals with heart or respiratory ailments are cautioned to stay indoors and refrain from physical exercise.

Although the air in the San Joaquin Valley is not yet that bad, the region is vulnerable to smog because it is relatively flat and surrounded on three sides by mountains. Fresno and Kern counties already exceed the national ozone standard more often than do Chicago, Dallas, Houston, New York and Philadelphia. Moreover, state air-quality officials estimate that smog in the valley has reduced by as much as 20% harvests of grapes, cotton, oranges, alfalfa and tomatoes.

“Because of its geography and climate, the San Joaquin Valley has a great potential to be worse than L.A.,� said Bill Sessa, spokesman for the California Air Resources Board. The board has been working with officials in the valley on a large-scale air-quality study to collect data and find scientific solutions to controlling air pollution. About 2.5 million people now live in the valley, up 22% since 1980, and the population is expected to grow another 43% by the year 2005.

Smog in the San Joaquin is exacerbated by temperature inversions--layers of warm air that form a lid over the pollution. Because of the inversion layer, the pollution accumulates in the summer at elevations of 4,000 feet to 6,000 feet for long periods of time.

“Offshore winds come down the mountains in the morning, bringing cool air to the valley,� said Patrick Temple, a UC Riverside professor of botany with the campus’ Statewide Air Pollution Research Center. “Ozone is transported to the mountains and settles there.�

Temple and other researchers recently completed the most thorough study yet of ozone’s damage to pines in the Sierra Nevada. The scientists found that ponderosa pine seedlings exposed to smog lost an average of 20% of their foliage. Needles turned brown and dropped off. Unable to maintain their needles, the trees slowly starve, Temple said.

Other kinds of air pollution also may be harming wildlife in the Sierra Nevada. Scientists suspect that acid precipitation, caused primarily by industrial and vehicle emissions in the valley, may be contributing to a mysterious disappearance of some frogs in the Sierra Nevada.

Yosemite park officials say water in the park’s lakes and streams becomes particularly acidic during a heavy snowmelt in the spring or during a rainfall after a long dry period. Acid accumulates in the atmosphere and falls to the ground in rain and snow.

The increasing rarity of certain species of frogs in the Sierra Nevada is part of a worldwide decline in amphibians. Although no one is really certain what triggered the decline, scientists suspect it could be linked to acid precipitation, pesticides or deforestation. Of particular concern in the Sierra Nevada has been the disappearance of two kinds of yellow-legged frogs and the Yosemite toad. Besides acid precipitation, a virus or some other kind of water pollution could be responsible for the decline in Yosemite.

“In years past, they were pretty common, and all of a sudden they are turning up missing,� said Jeffrey Keay, a wildlife biologist at Yosemite.

NEW EPA RULES: The EPA is expected to propose new smog controls, including possible “no-drive� days. A3