A plan for the struggling Sierra Nevada.

In a recently completed 3-year, $6.5 million study, scientists have examined the health of almost every nook and cranny of California's Sierra Nevada and declared the 400-mile-long mountain ecosystem in need of physical therapy. Last week, the authors presented their four-volume report to Congress, which had requested the analysis. Don C. Erman of the University of California, Davis led the more than 100 scientists who worked on the study, which was organized and funded by the U.S. Forest Service.

The report outlines many problems facing the Sierra Nevada and describes an array of possible solutions, including setting up larger forest reserves and slowing development. As for protecting the range, however, it has lobbed the ball into the public's court.

"We have identified problem areas and offered some alternatives for addressing them . . . . Left unresolved is the question of whether our society has the will and the capability to correct such problems," the scientists assert. They note that boosting investment in restoring the Sierra Nevada ecosystem-with activities such as controlling erosion, reclaiming mined areas, and thinning out stands of trees-would provide residents with jobs. Though not calling for a ban on the controversial logging of old-growth forests, the scientists do recommend setting up larger areas of protected forests. Loggers have already cut down much of the area's most accessible pine forests, they note.

Roughly half of California's 7,000 plant species, 200 of them rare, live in the Sierra Nevada. Of the Sierra's fauna, 17 percent, or 69 species, are at risk of extinction, primarily because of habitat loss. Cattle grazing is the primary threat to native land bird populations.

The waterways "are the most altered and impaired habitats of the Sierra," the authors state. Dams have changed the flow of many streams, which are now often clogged with sediment. Non-native fish, such as trout, are thriving, while some natives, such as Chinook salmon, "are now nearly extinct from Sierran rivers." Plans to prevent further degradation must protect the healthiest waterways, restore highly degraded ones, and include all watersheds. In the northern Sierra Nevada year-round, and during the winter in most remote areas, "air quality is some of the cleanest in the nation and even in the world," the authors assert. However, for much of the western slope, located near urban centers, visibility is "severely degraded." Strictly enforcing California's air pollution laws and staging additional controlled fires to decrease wildfires would help plants now suffering from air pollution, they say.

The report seems to be "sensitive to key issues of ecosystem management," as it discusses how all parts of a system work together, says Steward T. A. Pickett of the Institute of Ecosystem Studies in Millbrook, N.Y. He reviewed the document's eight-page summary, released along with the full report to the public this week.