The ecology of California can be understood by dividing the state into a number of ecoregions, which contain distinct ecological communities of plants and animals in a contiguous region. The ecoregions of California can be grouped into four major groups: desert ecoregions (such as the Mojave Desert), Mediterranean ecoregions (such as the Central Valley), forested mountains (such as the Sierra Nevada), and coastal forests.
Different authorities define the boundaries of ecoregions somewhat differently: this article follows the definitions of the World Wide Fund for Nature (WWF) and the United States Environmental Protection Agency (EPA)
California's high mountains block most moisture from reaching the eastern parts of the state, which are home to California's desert and xeric shrub ecoregions. The low desert of southeastern California is part of the Sonoran desert ecoregion, which extends into Arizona and parts of northern Mexico.California has two high deserts: the Mojave desert and the Great Basin Desert. The Mojave desert ecoregion is marked by the presence of Joshua trees. The dry cold Great Basin desert of California consists of the Owens Valley, and is classified into Great Basin shrub steppe by the WWF, and into the Central Basin and Range ecoregion by the EPA.
The deserts in California receive between 2 to 10 inches (51 to 254 mm) of rain per year. Plants in these deserts are brush and scrub, adapted to the low rainfall. Common plant species include creosote bush, blackbrush, greasewood, saltbush, big sagebrush, low sagebrush, and shadscale. Higher elevations have more precipitation, which allows drought-resistant trees to grow, such as western juniper and pinyon pine.
The coast of California from Monterey Bay south to the Mexican border, and inland from San Francisco Bay Area to the Sierra Nevada foothills contain California's Mediterranean ecoregions. This region is divided by the WWF into three California chaparral and woodlands ecoregions, plus the Central Valley grasslands.The EPA divides the region between the Central Valley (ecoregion 7), the Southern California chaparral (ecoregion 6), the Southern California mountains (ecoregion 8), and the Southern California coast (ecoregion 85).
The WWF distinguishes between different chaparral ecoregions based on species endemism.In the south, the California coastal sage and chaparral extends across the Mexican border into northwestern Baja California and Los Angeles. The coastal sage ecoregion is notable for having the highest number of native bees in the United States, although much of the ecoregion is now urbanized. The California montane chaparral and woodlands include the Transverse Ranges north of Los Angeles as well as the Santa Lucia Range on the Central Coast. The montane chaparral consists of a mosaic of sage scrub, chaparral, and montane species, depending on altitude. The California interior chaparral and woodlands form a ring around the Central Valley, covering the hills around the Bay Area as well as the foothills of the Sierra Nevada. The interior woodland ecoregion contains several endemic species, due to unique soil types such as serpentine.
These chaparral ecoregions contain numerous plant communities, including oak savanna,oak woodland, conifer woodlands, chamise chaparral, coastal sage scrub, and coastal grassland. These plant communities often occur as a mosaic, caused by fire.
California's Central Valley was once a large temperate grassland containing native bunchgrasses and vernal pools.Grizzly bear, gray wolf, tule elk, and pronghorn antelope used to inhabit the grasslands. The native grasslands and pools have now been largely replaced by livestock ranches and farms. The Carrizo Plain, where the native grass is preserved, is referred to as the "Serengeti of California".
The cooler and wetter mountains of northern California are covered by forest ecoregions. Both the WWF and the EPA divide the mountains into three ecoregions: the Sierra Nevada,the Klamath Mountains, and the Eastern Cascades Slopes and Foothills (occurring on the Modoc Plateau).
The Sierra Nevada are home to half of the vascular plant species of California, with 400 species that are endemic to the region.Like many mountain ranges, the plant communities of the Sierra group into biotic zones by altitude, because of the increasingly harsh climate as elevation increases. These biotic zones include montane forest dominated by conifers such as Jeffrey pine and Lodgepole pine, subalpine forest dominated by whitebark pine, up to alpine tundra which cannot support trees. The Sierra are also notable for giant sequoia trees: the most massive on earth.
The Klamath and Siskiyou Mountains are a notable biodiversity hotspot, containing one of the four most biodiverse temperate forests in the world.The diversity is caused by the ecoregion being adjacent to a number of other ecoregions, diverse soil, and having refugia caused by isolation in the last ice age. Some endemic species in the Klamath mountains are limited to only one mountain or valley.
The Eastern Cascades slopes of the Modoc Plateau are characterized by a mosaic of open ponderosa pine forest, grasslands, and shrublands.Although high, these slopes and mountains are in the rain shadow of the Cascade Range, and hence are drier and more open.
The coast of California north of San Francisco contains the Northern California coastal forests (as defined by the WWF) and the southern section of the Coast Range ecoregion (as defined by the EPA). This ecoregion is dominated by redwood forest, containing the tallest and some of the oldest trees in the world.
The redwood forests thrive in a thin belt up to 35 miles (56 km) wide next to the coast, where the trees are kept moist by winter rains and summer fog. The redwood forests are also notable for having the highest forest productivity in the world.
Chaparral is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean climate and infrequent, high-intensity crown fires. Chaparral features summer-drought-tolerant plants with hard sclerophyllous evergreen leaves, as contrasted with the associated soft-leaved, drought-deciduous, scrub community of coastal sage scrub, found often on drier, southern facing slopes within the chaparral biome. Three other closely related chaparral shrubland systems occur in central Arizona, western Texas, and along the eastern side of central Mexico's mountain chains (mexical), all having summer rains in contrast to the Mediterranean climate of other chaparral formations. Chaparral comprises 9% of California's wildland vegetation and contains 20% of its plant species. The name comes from the Spanish word chaparro, which translates to "place of the scrub oak".
The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface.
The Global 200 is the list of ecoregions identified by the World Wide Fund for Nature (WWF), the global conservation organization, as priorities for conservation. According to WWF, an ecoregion is defined as a "relatively large unit of land or water containing a characteristic set of natural communities that share a large majority of their species dynamics, and environmental conditions". For example, based on their levels of endemism, Madagascar gets multiple listings, ancient Lake Baikal gets one, and the North American Great Lakes get none.
The Great Basin Desert is part of the Great Basin between the Sierra Nevada and the Wasatch Range. The desert is a geographical region that largely overlaps the Great Basin shrub steppe defined by the World Wildlife Fund, and the Central Basin and Range ecoregion defined by the U.S. Environmental Protection Agency and United States Geological Survey. It is a temperate desert with hot, dry summers and snowy winters. The desert spans large portions of Nevada and Utah, and extends into eastern California. The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.
The California chaparral and woodlands is a terrestrial ecoregion of southwestern Oregon, northern, central, and southern California and northwestern Baja California (Mexico), located on the west coast of North America. It is an ecoregion of the Mediterranean forests, woodlands, and scrub biome, and part of the Nearctic realm.
The ecology of the Sierra Nevada, located in the U.S. states of California and Nevada, is diverse and complex: the plants and animals are a significant part of the scenic beauty of the mountain range. The combination of climate, topography, moisture, and soils influences the distribution of ecological communities across an elevation gradient from 500 to 14,500 feet. Biotic zones range from scrub and chaparral communities at lower elevations, to subalpine forests and alpine meadows at the higher elevations. Particular ecoregions that follow elevation contours are often described as a series of belts that follow the length of the Sierra Nevada. There are many hiking trails, paved and unpaved roads, and vast public lands in the Sierra Nevada for exploring the many different biomes and ecosystems.
The California Central Valley grasslands is a temperate grasslands, savannas, and shrublands ecoregion in California's Central Valley. It a diverse ecoregion containing areas of desert grassland, prairie, savanna, riparian forest, marsh, several types of seasonal vernal pools, and large lakes such as now-dry Tulare Lake, Buena Vista Lake, and Kern Lake.
The Madrean pine–oak woodlands are subtropical woodlands found in the mountains of Mexico and the southwestern United States. They are a biogeographic region of the tropical and subtropical coniferous forests and temperate broadleaf and mixed forests biomes, located in North America.
The Coast Ranges of California span 400 miles (644 km) from Del Norte or Humboldt County, California, south to Santa Barbara County. The other three coastal California mountain ranges are the Transverse Ranges, Peninsular Ranges and the Klamath Mountains.
The California Floristic Province (CFP) is a floristic province with a Mediterranean-type climate located on the Pacific Coast of North America with a distinctive flora similar to other regions with a winter rainfall and summer drought climate like the Mediterranean Basin. This biodiversity hotspot is known for being the home of the Sierran giant sequoia tree and its close relative the coast redwood. In 1996, the Province was designated as a biodiversity hotspot allowing it to join ranks among 33 other areas in the world with many endemic species. To be named a biodiversity hotspot, an area has to contain species and plant life that cannot be found anywhere else in the world. The California Floristic Province is home to over 3,000 species of vascular plants, 60% of which are endemic to the province.
Ephedra californica is a species of Ephedra, known by the common names California jointfir, California ephedra, desert tea, Mormon tea, and cañatillo.
The Klamath Mountains ecoregion of Oregon and California lies inland and north of the Coast Range ecoregion, extending from the Umpqua River in the north to the Sacramento Valley in the south. It encompasses the highly dissected ridges, foothills, and valleys of the Klamath and Siskiyou Mountains. It corresponds to the Level III ecoregion designated by the Environmental Protection Agency and to the Klamath-Siskiyou forests ecoregion designated by the World Wide Fund for Nature.
The California coastal sage and chaparral is a Mediterranean forests, woodlands, and scrub ecoregion located in southwestern California and northwestern Baja California (Mexico). It is part of the larger California chaparral and woodlands ecoregion.
The California montane chaparral and woodlands is an ecoregion defined by the World Wildlife Fund, spanning 7,900 square miles (20,000 km2) of mountains in the Transverse Ranges, Peninsular Ranges, and Coast Ranges of southern and central California. The ecoregion is part of the larger California chaparral and woodlands ecoregion, and belongs to the Mediterranean forests, woodlands, and scrub biome.
The California interior chaparral and woodlands ecoregion covers 24,900 square miles (64,000 km2) in an elliptical ring around the California Central Valley. It occurs on hills and mountains ranging from 300 feet (91 m) to 3,000 feet (910 m). It is part of the Mediterranean forests, woodlands, and scrub biome, with cool, wet winters and hot, dry summers. Temperatures within the coast can range from 53° to 65 °F and 32° to 60 °F within the mountains. Many plant and animal species in this ecoregion are adapted to periodic fire.
The Great Basin montane forests is an ecoregion of the Temperate coniferous forests biome, as designated by the World Wildlife Fund (WWF).
Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial factor in shaping plant community, biodiversity, metabolic processes and ecosystem dynamics for montane ecosystems. Dense montane forests are common at moderate elevations, due to moderate temperatures and high rainfall. At higher elevations, the climate is harsher, with lower temperatures and higher winds, preventing the growth of trees and causing the plant community to transition to montane grasslands, shrublands or alpine tundra. Due to the unique climate conditions of montane ecosystems, they contain increased numbers of endemic species. Montane ecosystems also exhibit variation in ecosystem services, which include carbon storage and water supply.
The Cordillera Oriental montane forests (NT0118) is an ecoregion in Venezuela and Colombia along the east slopes of the eastern cordillera of the Andes. The extensive region of submontane and montane forests includes distinctive flora and fauna in the north, center and southern sections. The ecoregion is home to numerous endemic species of fauna. Despite extensive changes due to logging, farming and ranching, large areas of the original habitat remain intact, and the ecoregion has rich biodiversity.