Baja California Desert
The Baja California Desert ecoregion, located on most of the western side of the Baja Peninsula, contains varied habitats such as mountains, plains and coastal dunes. This desert is one of the largest and best preserved in Mexico, and due to its isolation, contains a high level of species richness and endemism. The largest protected area in Mexico is located within this ecoregion, providing habitat for a number of endemic species such as the San Quintín Kangaroo Rat, Baja California Rock Squirrel, as well as a plethora of spider, scorpion and bee species. Unfortunately, intensive cattle ranging and unregulated hunting have taken its toll on much of the original natural environment.
Location and general depiction
The Baja California Desert ecoregion occurs on the western portion of the Baja California peninsula, and occupies most of the Mexican states of Baja California Sur and Baja California Norte. Elevation is variable, ranging from mountain ranges on the western central part varying from 1000 to 1500 metres (m), plains of median elevation (300 to 600 m) and vast extensions of coastal dunes.
A series of ophiolytes – formations of gabrum, ultramafic rocks, and volcanic lava – surround the most prominent orographic feature: The San Andres mountain range. Overall, the climate is dry with variable temperature. The isolated nature of the peninsula, and its proximity to the sea, maintains a certain degree of humidity, and is responsible for keeping temperatures generally stable throughout the day.
The predominant vegetation associations are composed of xeric scrub, which have been subdivided in diverse categories according to dominant species and the ecological conditions in which they occur. Thick-stemmed trees and shrubs, growing on rocky volcanic soils, cover the highest parts of the mountain ranges. Dominant plant species are Ambrosia camphorata, Common Stork's-bill (Erodium cicutarium), and Astragalus prorifer. The Boojumtree (Fouquieria columnaris) can be also found at elevations up to 1200m. Many species of cacti are present. Dominant species within the Baja California Desert vary with elevation. Epiphytes such as Small Ballmoss (Tillandsia recurvata) and Cudbear (Rocella tinctoria) grow in low elevation, humid areas, and account for a majority of the perennial vegetation. Areas previously submerged under the sea (in the Miocene era) are now covered by highly saline and alkaline-tolerant species, such as Ambrosia magdalenae, El Vizcaino Agave (Agave vizcainoensis), Datilillo (Yucca valida), Pitaya Agria (Stenocereus gummosus), and Porter's Muhly (Muhlenbergia porteri). Dune vegetation includes Creosote Bush (Larrea tridentata), Barclay's Saltbush (Atriplex barclayana), Rush Milkweed (Asclepias subulata) and Nicolletia trifida.
One of the largest and best preserved deserts in Mexico, the Baja California Desert is home to many endemic and endangered species. The peninsula’s isolation is largely responsible for the high levels of endemism and diversity. Approximately 500 species of plants, four amphibians, 43 reptiles, around 200 birds and over fifty mammals have adapted to difficult ecological conditions – from inhospitable hot and dry sand dunes, to nutrient-deficient soils in the mountains.
Twenty-three percent of plant species in the Baja California Desert are endemic. In particular, the families Lamiaceae and Fouquieriaceae show considerable radiation within the ecoregion. With moderate faunal species richness, the Baja California Desert is home to 364 vertebrate taxa. In addition, scorpions and spiders show marked radiation here. The close relationship between animals and cacti in the Baja California Desert is recognized as an important ecological process for maintaining the diversity of both groups.
There are numerous special status taxa that are found in the Baja California Desert, denoted variously as Near Threatened (NT), Vulnerable (VU), Endangered (EN), or Critically Endangered (CR).
There are a number of reptilian taxa found in the Baja California Desert including the endemic Baja California Brush Lizard (Urosaurus lahtelai). The Baja California Legless Lizard (Anniella geronimensis EN) is also endemic to the ecoregion, and is restricted to a narrow strip around 87 kilometres (km) long, ranging from about six km north of Colonia Guerrero, southerly to a point south of Punta Baja at the northern edge of Bahia El Rosario. This legless lizard extends to at most four km inland in the Arroyo Socorro, but otherwise found only in the coastal zone; A. geronimensis also occurs on Isla San Gerónimo.
Also found here is the San Lucan Leaf-toed Gecko (Phyllodactylus unctus NT), a species not endemic to the ecoregion, but restricted to the southern Baja Peninsula and the Gulf of California islands of Partida Sur, Gallo, Espiritu Santo, Ballena, Gallina and Cerralvo.
There are only a few amphibians found in the ecoregion. Anuran taxa occurring here include: California Chorus Frog (Pseudacris cadaverina); Pacific Chorus Frog (Pseudacris regilla); and Canyon Treefrog (Hyla arenicolor). Also found here is the Plateau Toad (Anaxyrus compactilis), an endemic to the lower central Mexican Plateau and Baja California Desert; another toad occurring in the ecoregion is the Western Toad (Anaxyrus boreas NT). The Channel Islands Slender Salamander (Batrachoseps pacificus) was earlier thought to occur in this ecoregion, but genetic data shows that this taxon is strictly endemic to the Channel Islands of California.
Endemic mammals include San Quintín Kangaroo Rat (Dipodomys gravipes CR), and Baja California Rock Squirrel (Spermophilus atricapillus EN). Other mammals that are classified as special status are the Lesser Long-nosed Bat (Leptonycteris yerbabuenae VU).
Some shallow coastal saltwater lagoons protruding into the Baja California Desert along the Pacific Ocean provide key breeding habitat for the Grey Whale (Eschrichtius robustus CR). One of the largest such breeding waters is the remote San Ignacio Lagoon, extending many kilometres inland and rarely exceeding fifteen metres in depth.
Important sites for conservation include the Ojo de Liebre lagoon, along the Pacific coast, which is home to millions of overwintering ducks and geese. Bird species in the Baja California Desert include such notable raptor taxa as Golden Eagle (Aquila chrysaetos), Peregrine Falcon (Falco peregrinus), Southern Crested Caracara (Caracara plancus), Osprey (Pandion haliaeutus), and Burrowing Owl (Athene cunicularia).
The Baja California Desert remains partially intact, despite intensive human activity in portions of this desert. There are two federal protected areas, including El Vizcaíno, the largest protected area in Mexico. A number of areas important for bird conservation have been identified ithin this ecoregion, including San Quintin, Bahia Magdalena-Almejas, Complejo Lagunar Ojo de Liebre, Complejo Lagunar San Ignacio, Sierra La Giganta, Sierra San Pedro Martir.
Ecological threat profile
Livestock ranching, salt extraction, and over-hunting are the principal threats. Cattle have effectively displaced populations of Mule deer (Odocoileus hemionus) and Bighorn sheep (Ovis canadensis). Puma (Felis concolor) populations have been reduced as a result of over-hunting. Salt extraction, the main industrial activity of the region, has a negative impact on the breeding and migration of the Gray whale (Eschrichtius robustus) along the coast. An acute threat is the continuing loss of native grassland habitat due to intensive cultivation of Buffel-grass for feeding cattle.
Justification of ecoregion delineation
This ecoregion follows the linework and treatment by the CONABIO workshops on this region, as well as the WWF designation of NA1301 within the Deserts and Xeric Shrublands biome. It should be noted that in some classification schemes the Baja California Desert is considered a sub-unit of the Sonoran Desert.
- California coastal sage and chaparral, ecoregion to the north
- Gulf of California xeric shrub, ecoregion to the east and south
- San Lucan xeric scrub , ecoregion somewhat to the south on the Baja Peninsula, but not directly adjacent
- Sonoran Desert, ecoregion with small contact perimeter at the northwest
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