From page 1 of the report:

"The Sierra Nevada Ecosystem Project assessed all vegetated areas of the Sierra Nevada (15.6 million acres); 89.7% of the region is covered by plants (plate 5.1). The rest is rocky barrens, water, or settled lands. Eighty-eight natural plant community types have been described within the Sierra; about one-quarter of them have ranges of less than 6,000 acres. Conversely, twelve community types collectively contribute twothird of the region’s total vegetated acreage.

Of California’s 7,000 vascular plant species, about 50% occur in the Sierra Nevada. Of these, more than 400 species are found only in the Sierra Nevada, and 200 are rare.  Threats to Plant Diversity Three plant species marginally within the Sierra Nevada (Monardella leucocephala, Mimulus whipplei, and Erigeron mariposanus) appear to have become extinct in the last hundred years.  Vertebrate Diversity About 300 terrestrial vertebrate species (including mammals, birds, reptiles, and amphibians) use the Sierra Nevada as a significant part of their range, although more than 100 others include the Sierra Nevada as a minor part of more extensive ranges elsewhere.

Three modern vertebrate species once well distributed in the range are now extinct from the Sierra Nevada: Bell’s vireo, California condor, and grizzly bear.  Vertebrate Species at Risk Sixty-nine species of terrestrial vertebrates (17% of the Sierra fauna) are considered at risk by state or federal agencies, which list them as endangered, threatened, of “special concern,” or “sensitive.

Eighty-five terrestrial vertebrate species require west-slope foothill savanna, woodland, chaparral, or riparian habitats to retain population viability; 14% of these are considered at risk.

The most important identified cause of the decline of Sierran vertebrates has been loss of habitat, especially foothill and riparian habitats and late successional forests.

Activities occurring in the Sierra Nevada that pose the greatest indirect and direct threats to genetic diversity are those that break the chain of natural selection and adaptation.

Genetic guidelines that alert managers to activities likely to have genetic consequences and inform managers about preferred management of seeds, plants, mushrooms, animals, insects, and other germ plasm have been mostly lacking, inadequate, or poorly implemented in land management of the Sierra.

Excluding marginal plant communities mainly distributed in the Mojave Desert and Great Basin, the Sierra Nevada encompasses eighty-eight plant community types as defined by California's Natural Heritage Division.

Many of the foothill community types fall largely within private lands, notably grassland (88% of the mapped distribution on private lands), valley oak woodland (98%), blue oak woodland (89%), interior live oak woodland (71%), and foothill pine–oak woodland (82%).

Livestock grazing has been implicated in plant compositional and structural changes in foothill community types, meadows, and riparian systems, and grazing is the primary negative factor affecting the viability of native Sierran land bird populations.

Six forest types are mostly found on lands available for firewood cutting or timber harvest, including interior live oak (81%), black oak (56%), east-side ponderosa pine (72%), Sierran mixed conifer (67%), Sierran white fir (62%), and lower cismontane mixed conifer–oak (70%).

Nearly 800,000 acres of oak woodlands in the Sierra Nevada have been converted to other land uses and vegetation types over the last forty years, a decline of almost 16%.