Nation

Sequoia smog threatens health of redwoods

SEQUOIA NATIONAL PARK, Calif. - The Sierra Nevada forest that is home to the biggest and oldest living things on earth - the giant Sequoia redwoods - also suffers a dubious distinction. It has the worst air pollution of any national park in the country.

Mountaintops that should offer awe-inspiring views of California’s geologic grandeur often are muddled by a disorienting gray soup of smog, and scientists are not sure with the effect will be on the redwoods that have been around for 3,000 years or more.

On a clear day, the view from Beetle Rock in Sequoia National Park extends west for 105 miles across the patchwork of crops in California’s agricultural heartland to the Coast Mountains and the Pacific Ocean beyond. The problem is there are few clear days, even at 6,200 feet.

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“Ozone levels here are comparable to urban settings such as LA,’’ said Emily Schrepf of the nonprofit advocacy group the National Park Conservation Association. “It’s just not right.’’

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Smog is so bad that signs in visitors centers caution guests when it is not safe to hike. The government employment website warns job applicants that the workplace is unhealthy. And park workers are schooled every year on the lung and heart damage the pollution can cause.

Ozone also is to blame for weakening many stands of the park’s Jeffrey and ponderosa pines, leaving telltale yellowing of their long needles. Instead of absorbing carbon dioxide, they soak up ozone through the stoma in their needles, which inhibits photosynthesis. Ozone also stresses young redwood seedlings.

Although weakened trees are more susceptible to drought and pests, the long-term impact on the trees is unclear.