Southern California Coastal–Baja California is a

freshwater ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

in Western North America. It encompasses parts of central and southern California, west of the Coast Ranges, and the majority of

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

's Baja California Peninsula, extending from the southern end of

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area. San Francisco itself is further north along the coast, by about 75 miles (120 km), accessible via California S ...

to the southern tip of the Baja California Peninsula."Southern California Coastal - Baja California". Freshwater Ecoregions of the World. Accessed 14 September 2021

/ref>

Geography

Most rivers and streams are short and relatively small, originating in the mountains and flowing to the sea. The climate ranges from semi-humid to arid, and rainfall is highly seasonal and can be irregular, so many streams have big seasonal variations in flow, or are intermittent. The ecoregion has an area of . 76% of the ecoregion is in Mexico's states of

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

and

Baja California Sur Baja California Sur, officially the Free and Sovereign State of Baja California Sur, is a state in Mexico. It is the 31st and last state to be admitted, in 1974. It is also the second least populated Mexican state and the ninth-largest state by ...

, and 24% is in California. Elevations range from sea level to over 3300 meters. The ecoregion includes the western slope of the

Santa Lucia Mountains The Santa Lucia Range (sæntə luˈsiːə) or Santa Lucia Mountains is a rugged mountain range in coastal Central California, running from Carmel southeast for to the Cuyama River in San Luis Obispo County. The range is never more than fro ...

in central California, the seaward slopes of the

Transverse Ranges The Transverse Ranges are a group of mountain ranges of Southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Ba ...

and northern

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Pacific Coast Range ...

in Southern California and Northern Baja California, and both the western and eastern (Pacific and

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

) sides of the Peninsular Ranges on the Baja California Peninsula. It also includes the

Channel Islands of California The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. They define the Santa Barbara Channel between the islands and the California mainland. The ...

, and

Cedros Island Cedros Island (''Isla de Cedros'', "island of cedars" in Spanish (language), Spanish) is an island in the Pacific Ocean belonging to the state of Baja California, Mexico. The dry and rocky island had a population of 1,350 in 2005 and has an area o ...

off the western coast of Baja California. Larger rivers include the

Santa Ynez River The Santa Ynez River is one of the largest rivers on the Central Coast, California, Central Coast of California. It is long, ArcExplorer Geographic information system, GIS data viewer. flowing from east to west through the Santa Ynez Valley, re ...

Santa Barbara County Santa Barbara County, officially the County of Santa Barbara (), is a county located in Southern California. As of the 2020 United States census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa M ...

, the

Ventura River The Ventura River, in western Ventura County in southern California, United States, flows from its headwaters to the Pacific Ocean. The smallest of the three major rivers in Ventura County, it flows through the steeply sloped, narrow Ventura ...

Ventura County Ventura County () is a county located in the southern part of the U.S. state of California. As of the 2020 census, the population was 843,843. The largest city is Oxnard, and the county seat is the city of Ventura. Ventura County comprises ...

, the Santa Clara River in

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

and Ventura counties, and the

, San Gabriel, and Santa Ana rivers in the

Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east–west trending chains of mountai ...

.Howard, J., and C. Revenga (2009). "California’s freshwater biodiversity in a continental context". Science for Conservation Technical Brief Series. The Nature Conservancy of California. San Francisco, CA. 29 pp + Appendices. Accessed 18 September 2021

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Fauna

Fish species endemism, endemic to the ecoregion include the Santa Ana sucker (''Catostomus santaanae''), California killifish (''Fundulus parvipinnis''), Peninsular clingfish (''Gobiesox juniperoserrai''), and Baja California killifish (''Fundulus lima''). Two subspecies of

three-spined stickleback The three-spined stickleback (''Gasterosteus aculeatus'') is a fish native to most inland and coastal waters north of 30°N. It has long been a subject of scientific study for many reasons. It shows great morphological variation throughout its ra ...

(''Gasterosteus aculeatus'') are endemic to southern California – the unarmored threespine stickleback (''G. a. williamsoni'') and the Santa Ana stickleback (''G. a. santaeannae'').

Anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

steelhead trout Steelhead, or occasionally steelhead trout, is the anadromous form of the coastal rainbow trout or Columbia River redband trout (''O. m. gairdneri'', also called redband steelhead). Steelhead are native to cold-water tributaries of the Pacif ...

(''Onchorhynchus mykiss'') are found some southern California streams. The ecoregion is the southern limit of their range, and the Southern California steelhead populations are genetically adapted to warmer water than most steelhead and salmon species. The San Pedro Mártir trout is endemic to the

Sierra San Pedro Mártir Sierra (Spanish for "mountain range" or " mountain chain" and "saw", from Latin '' serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nie ...

in northern Baja California. Some authorities consider the San Pedro Mártir trout a separate species (''Onchorhynchus nelsoni''), while others consider it a subspecies of steelhead (''Onchorhynchus mykiss nelsoni'').Kurlansky, Mark (2020). ''Salmon''. Patagonia, Ventura CA.

References

{{DEFAULTSORT:Southern California Coastal-Baja California Freshwater ecoregions Ecoregions of California Ecoregions of Mexico Drainage basins of the Pacific Ocean