Of the 48 conterminous states, California embraces the greatest diversity of climate and terrain. The state's six life zones are the lower Sonoran (desert); upper Sonoran (foothill regions and some coastal lands); transition (coastal areas and moist northeastern counties); and the Canadian, Hudsonian, and Arctic zones, comprising California's highest elevations.
Plant life in the arid climate of the lower Sonoran zone features a diversity of native cactus, mesquite, and paloverde. The Joshua tree (Yucca brevifolia) is found in the Mojave Desert. Flowering plants include the dwarf desert poppy and a variety of asters. Fremont cottonwood and valley oak grow in the Central Valley. The upper Sonoran zone includes the unique chaparral belt, characterized by forests of small shrubs, stunted trees, and herbaceous plants. Nemophila, mint, phacelia, viola, and the golden poppy (Eschscholtzia californica)—the state flower—also flourish in this zone, along with the lupine, more species of which occur here than anywhere else in the world.
The transition zone includes most of the state's forests, with such magnificent specimens as the redwood (Sequoia sempervirens) and "big tree" or giant sequoia (Sequoia gigantea), among the oldest living things on earth (some are said to have lived at least 4,000 years). Tanbark oak, California laurel, sugar pine, madrona, broad-leaved maple, and Douglas fir are also common. Forest floors are carpeted with swordfern, alumroot, barrenwort, and trillium, and there are thickets of huckleberry, azalea, elder, and wild currant. Characteristic wild flowers include varieties of mariposa, tulip, and tiger and leopard lilies.
The high elevations of the Canadian zone are abundant with Jeffrey pine, red fir, and lodgepole pine. Brushy areas are covered with dwarf manzanita and ceanothus; the unique Sierra puffball is also found here. Just below timberline, in the Hudsonian zone, grow the whitebark, foxtail, and silver pines. At approximately 10,500 ft (3,200 m) begins the Arctic zone, a treeless region whose flora includes a number of wild flowers, including Sierra primrose, yellow columbine, alpine buttercup, and alpine shooting star.
Common plants introduced into California include the eucalyptus, acacia, pepper tree, geranium, and Scotch broom. Among the numerous species found in California that are federally classified as endangered are the Contra Costa
Mammals found in the deserts of the lower Sonoran zone include the jackrabbit, kangaroo rat, squirrel, and opossum. The Texas night owl, roadrunner, cactus wren, and various species of hawk are common birds, and the sidewinder, desert tortoise, and horned toad represent the area's reptilian life. The upper Sonoran zone is home to such mammals as the antelope, brown-footed woodrat, and ring-tailed cat. Birds distinctive to this zone are the California thrasher, bush tit, and California condor.
Animal life is abundant amid the forests of the transition zone. Colombian black-tailed deer, black bear, gray fox, cougar, bobcat, and Roosevelt elk are found. Garter snakes and rattlesnakes are common, as are such amphibians as the water-puppy and redwood salamander. The kingfisher, chickadee, towhee, and hummingbird represent the bird life of this region.
Mammals of the Canadian zone include the mountain weasel, snowshoe hare, Sierra chickaree, and several species of chipmunk. Conspicuous birds include the blue-fronted jay, Sierra hermit thrush, water ouzel, and Townsend solitaire. Birds become scarcer as one ascends to the Hudsonian zone, and the wolverine is now regarded as rare. Only one bird is native to the high Arctic region—the Sierra rosy finch—but others often visit, including the hummingbird and Clark nutcracker. Principal mammals of this region are also visitors from other zones; the Sierra coney and white-tailed jackrabbit make their homes here. The bighorn sheep also lives in this mountainous terrain; as of April 2003, the bighorn sheep was listed as endangered by the US Fish and Wildlife Service. Among fauna found throughout several zones are the mule deer, coyote, mountain lion, red-shafted flicker, and several species of hawk and sparrow.
Aquatic life in California is abundant, from the state's mountain lakes and streams to the rocky Pacific coastline. Many trout species are found, among them rainbow, golden, and Tahoe; migratory species of salmon are also common. Deep-sea life forms include sea bass, yellowfin tuna, barracuda, and several types of whale. Native to the cliffs of northern California are seals, sea lions, and many types of shorebirds, including several migratory species.
The Resources Agency of California's Department of Fish and Game is especially active in listing and providing protection for rare, threatened, and endangered fauna. Joint efforts by state and federal wildlife agencies have established an ambitious—if somewhat controversial—recovery program to revitalize the dwindling population of the majestic condor, the largest bird native to the US.
As of April 2003, 118 California animals were on the federal endangered list; 181 plants were listed as endangered or threatened. Endangered animals include the San Joaquin kit fox, Point Arena mountain beaver, Pacific pocket mouse, salt marsh harvest mouse, Morro Bay kangaroo rat (and five other species of kangaroo rat), Amargosa vole, California least tern, California condor, San Clemente loggerhead shrike, San Clemente sage sparrow, San Francisco garter snake, five species of salamander, three species of chub, and two species of pupfish. Eleven butterflies listed as endangered and two as threatened on the federal list are California species. Among threatened animals are the coastal California gnatcatcher, Paiute cutthroat trout, southern sea otter, and northern spotted owl. California has a total of 290,821 acres (117,6791 ha) of National Wildlife Refuges.