Ecology

Habitat

Baja California Desert Habitat

This taxon is found in the Baja California Desert ecoregion, located on most of the western side of the Baja Peninsula, containing 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. 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 arid with variable temperature. The isolated nature of the peninsula, and its proximity to the sea, maintains a measure of humidity, and creates a stable diurnal temperature.

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.

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 avian 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).

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© C. Michael Hogan & World Wildlife Fund

Supplier: C. Michael Hogan

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