Damage to the vegetation of the parks is of concern. Some plants, such as certain species of oaks and ponderosa and Jeffrey pines, are more sensitive to ozone than others. Even individual plants differ in their sensitivity to pollutants. A study conducted in Sequoia and Kings Canyon National Parks in the mid-1980s revealed that two of every five ponderosa and Jeffrey pines surveyed exhibited needle damage caused by ozone. Injury was most severe on western slopes closest to the San Joaquin Valley.
Research continues on the giant sequoias.
Experiments have documented that sequoia seedlings show damage to needles and reduced growth when exposed to elevated levels of ozone. Acidic Deposition Research, including a seven-year, intensive study of the Emerald Lake watershed, was conducted in the 1980s to establish the effects of acidic deposition upon subalpine vegetation and lakes. Such baseline data will enable managers to assess changes in atmospheric deposition and the subsequent effects on natural ecosystems. The scenic vistas of the parks are viewed by nearly two million visitors annually. The vistas, especially in the summer, are highly obscured by regional haze.