Ecoregion Description

159: Southern California Coastal - Baja California

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Salvador Contreras Balderas, Universidad Autónoma de Nuevo León. Additional text was modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment

Countries:

Mexico; United States

Boundaries:

This coastal ecoregion begins just south of Monterey, California and encompasses southwestern California and the entire Baja Peninsula in Mexico. The Channel Islands and Isla Cedros are also part of this ecoregion.

Drainages flowing into:

Drainages flow into the Pacific Ocean and Gulf of California.

Main rivers or other water bodies:

There are numerous small rivers and coastal basins within the ecoregion. One of the few major rivers is the Santa Ynez River in Central California.

Topography:

The Peninsular Ranges extend down the center of the ecoregion from southern California through the length of the Baja California Peninsula. Elevations reach over 3300 m asl. Some of the ranges within this chain include the Laguna Mountains, Santa Rosa Mountains, Sierra de la Giganta, Sierra San Pedro Màrtir, and Sierra de Juariz.

Climate:

This ecoregion, sometimes grouped with the Sonoran Desert, is characterized by extreme aridity (Köppen 1936). The mountain chains running through the center of the ecoregion influence the various weather patterns: the northwestern portion of the ecoregion experiences a Mediterranean climate; valleys in central Baja experience a more humid climate; and dry, desert conditions occur along the eastern and southern portion.

Freshwater habitats:

There are almost no permanent watercourses in Baja California. Yet, in spite of the arid conditions, the ecoregion contains high grade mountain creeks, coastal plain creeks, springs, and coastal lagoons.

Terrestrial Habitats:

In the northern part of the ecoregion, coastal sage scrub, chamise chaparral, and oak woodlands predominate over much of the landscape. Other habitats include montane conifer forests, Torrey pine (Pinus torreyana) woodlands, cypress (Cupressu spp.) woodlands, riparian woodlands, and grasslands. Western Baja is dominated by xeric scrubs, including Ambrosia camphorata, Erodium cicutarium, Astragalus prorifer, and many species of cacti. A majority of the perennial vegetation are epiphytes like Tillandsia recurvata and Rocella tinctoria that grow in low, humid areas. The eastern side of the Peninsular Ranges is part of the Sonoran Desert, and includes species like ironwood (Palo fierro), cardón (Pachycereus pringlei), and saguaro (Carnegiea gigantea spp.).

Fish Fauna:

The ecoregion’s peninsular fish fauna is a textbook case on the scarcity of species in peninsular freshwater environments. Most of the species occur at the edge of their respective ranges. When the peninsula separated from the continental plates it did not keep the main continental primary fishes, which inhabit the Lower Colorado River. Instead, much of the fish fauna is marine-derived, and is represented by the killifish (Fundulidae), lamprey (Petromyzontidae), sculpin (Cottidae), and salmonid (Salmonidae) families. This ecoregion is the southernmost range for some anadromous fish, such as the steelhead (Oncorhynchus mykiss) and the Pacific lamprey (Lampetra tridentata).           

Description of endemic fishes:

Most of the endemism of the region is found in the Los Angeles basin, in California. There are four known endemic fish species in the ecoregion. Endemic fish that occur in the Los Angeles basin include the Santa Ana sucker (Catostomus santaanae) and California killifish (Fundulus parvipinnis). Peninsular clingfish (Gobiesox juniperoserrai), killifish (F. lima), threespine stickleback (Gasterosteus aculeatus microcephalus), and San Pedro Mártir rainbow trout (Onchorhynchus nelsoni) are also endemic to the ecoregion.

Ecological phenomena:

The freshwater fish fauna include genetically important populations as well as species with marginal distributional records.

Evolutionary phenomena:

Many of the fish species are of marine origin.

Justification for delineation:

Ecoregion delineations were based on qualitative similarity/dissimilarity assessments of major basins, using the standard administrative hydrographical regions of the Mexican federal government.

Level of taxonomic exploration:

Excellent

References/sources:

Abell, R. A., Olson, D. M., et al. (2000). "Freshwater Ecoregions of North America: A Conservation Assessment" Washington, DC, USA: Island Press.

Minckley, W. L. (2002)"Fishes of the lower most Colorado River, its delta, and estuary: a commentary on biotic change" In Lozano-Vilano, M. (Ed.). Libro Jubilar en Honor al Dr. Salvador Contreras Balderas. Dir. Gral. De Publicaciones. (pp. 63-78) Monterrey, México: Universidad A. de Nuevo León.

Ricketts, Taylor H. Dinerstein Eric Olson David M. Loucks Colby J. (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.

Ruiz-Campos, G., Contreras-Balderas, S., et al. (2000). "Ecological and distributional status of the continental fishes of northwestern Baja California, Mexico" Bulletin of the Southern California Academy of Sciences 99(2) 59-90.