California is a state in the Western United States. California borders Oregon to the north, Nevada and Arizona to the east, the Mexican state of Baja California to the south; and has a coastline along the Pacific Ocean to the west. With over 39.5 million residents across a total area of approximately 163,696 square miles, it is the most populous and the third-largest U.S. state by area.
California boasts several superlatives in its collection of flora: the largest trees, the tallest trees, and the oldest trees. California's native grasses are perennial plants. After European contact, these were generally replaced by invasive species of European annual grasses; and, in modern times, California's hills turn a characteristic golden-brown in summer.
Because California has the greatest diversity of climate and terrain, the state has six life zones which are the lower Sonoran Desert; upper Sonoran, transition and the Canadian, Hudsonian, and Arctic Zones, comprising the state's highest elevations.
Plant life in the dry climate of the lower Sonoran zone contains a diversity of native cactus, mesquite, and paloverde. The Joshua tree is found in the Mojave Desert. Flowering plants include the dwarf desert poppy and a variety of asters. Fremont cottonwood and valley oak thrive in the Central Valley. The upper Sonoran zone includes the chaparral belt, characterized by forests of small shrubs, stunted trees, and herbaceous plants. Nemophila, mint, Phacelia, Viola, and the California poppy 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 California's forests with the redwood and the 'big tree' or giant sequoia, among the oldest living things on earth, Tanbark oak, California laurel, sugar pine, madrona, broad-leaved maple, and Douglas-fir also grow here. Forest floors are covered with swordfern, alumnroot, 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 allow the Jeffrey pine, red fir, and lodgepole pine to thrive. Brushy areas are abundant with dwarf manzanita and ceanothus; the unique Sierra puffball is also found here. Right below the timberline, in the Hudsonian zone, the whitebark, foxtail, and silver pines grow. At about 10,500 feet, begins the Arctic zone, a treeless region whose flora include a number of wildflowers, including Sierra primrose, yellow columbine, alpine buttercup, and alpine shooting star.
Common plants that have been introduced to the state include the eucalyptus, acacia, pepper tree, geranium, and Scotch broom. The species that are federally classified as endangered are the Contra Costa wallflower, Antioch Dunes evening primrose, Solano grass, San Clemente Island larkspur, salt marsh bird's beak, McDonald's rock-cress, and Santa Barbara Island liveforever. As of December 1997, 85 plant species were listed as threatened or endangered.
In the deserts of the lower Sonoran zone, the mammals include the jackrabbit, kangaroo rat, squirrel, and opossum. Common birds include the owl, roadrunner, cactus wren, and various species of hawk. The area's reptilian life include the sidewinder viper, desert tortoise, and horned toad. The upper Sonoran zone boasts mammals such as the antelope, brown-footed woodrat, and ring-tailed cat. Birds unique to this zone are the California thrasher, bushtit, and California condor.
In the transition zone, there are Colombian black-tailed deer, black bears, gray foxes, cougars, bobcats, and Roosevelt elk. Reptiles such as the garter snakes and rattlesnakes inhabit the zone. In addition, amphibians such as the water puppy and redwood salamander are common too. Birds such as the kingfisher, chickadee, towhee, and hummingbird thrive here as well.
The Canadian zone mammals include the mountain weasel, snowshoe hare, and several species of chipmunks. Conspicuous birds include the blue-fronted jay, mountain chickadee, hermit thrush, American dipper, and Townsend's solitaire. As one ascends into the Hudsonian zone, birds become scarcer. While the gray-crowned rosy finch is the only bird native to the high Arctic region, other bird species such as Anna's hummingbird and Clark's nutcracker. Principal mammals found in this region include the Sierra coney, white-tailed jackrabbit, and the bighorn sheep. As of April 2003, the bighorn sheep was listed as endangered by the U.S. Fish and Wildlife Service. The fauna found throughout several zones are the mule deer, coyote, mountain lion, northern flicker, and several species of hawk and sparrow.
Aquatic life in California thrives, from the state's mountain lakes and streams to the rocky Pacific coastline. Numerous trout species are found, among them rainbow, golden, and cutthroat. Migratory species of salmon are common as well. 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 migratory species.
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 kitfox, Point Arena mountain beaver, Pacific pocket mouse, salt marsh harvest mouse, Morro Bay kangaroo rat, Amargosa vole, California least tern, California condor, 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 are also endangered and two that are threatened are on the federal list. 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 of National Wildlife Refuges. As of September 2010, 123 California animals were listed as either endangered or threatened on the federal list. Also, as of the same year, 178 species of California plants were listed either as endangered or threatened on this federal list.