Introduction

Near San Fernando, Baja California, Mexico (Source: Photograph by Timothy Green)

This ecoregion is 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 of 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 and provides habitat for a number of endemic species such as the San Quintín Kangaroo Rat, Baja California rock squirrel, as well as a wealth of spider, scorpion, and bee species. Unfortunately, cattle ranging and unregulated hunting have taken its toll on much of this habitat.

Location and General Description

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 (1000 - 1500 meters (m)), plains of median elevation (300 – 600m), 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 more or less stable throughout the day.

The main vegetation associations are composed of xeric scrubs, 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 species are Ambrosia camphorata, Erodium cicutarium, and Astragalus prorifer. Fouquieria columnaris can be also found up to 1200m. Many species of cacti are present. Dominant species vary with elevation. Epiphytes like Tillandsia recurvata and Rocella tinctoria grow in low, humid areas, and account for a majority of the perennial vegetation. Areas previously submerged under the sea (in the Miocene) are now covered by highly salt- and alkaline-tolerant species (e.g. Ambrosia magdalenae, Agave vizcainoensis, Yucca valida, Stenocereus gummosus, and Muhlenbergia porteri). Dune vegetation includes Larrea tridentata, Atriplex barclayana, Asclepia subulata and Nicolletia trifida, among other species.

Biodiversity Features

Western diamondback rattlesnake (''Crotalus atrox''), Baja California, Mexico (Source: Photograph by Gerald and Buff Corsi)

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. Close to 500 species of plants, 4 amphibians, 43 reptiles, around 200 birds and over 50 mammals have adapted to difficult ecological conditions – from almost inhospitable hot and dry sand dunes, to nutrient-deficient soils in the mountains. Twenty-three percent of plant species in Baja California are endemic. In particular, the families Lamiaceae and Fouquieriaceae show considerable radiation within the ecoregion.

Endemic mammals include San Quintín Kangaroo Rat (Dipodomys gravipes), and Baja California rock squirrel (Spermophilus atricapillus). A high number of bee species are also endemic to the ecoregion. 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. 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 include such rare ones as golden eagle (Aguila chrysaetos), peregrine falcon (Falco peregrinus), crested caracara (Caracara plancus), osprey (Pandion haliaeutus), and burrowing owl (Athene cunicularia).

Current Status

The Baja California Desert remains partially intact, despite intensive human activity. 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.

Types and Severity of Threats

Livestock ranching, salt extraction, and 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 gray whales (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.

Further Reading

• Ayala, R., T. L. Griswold, and S. H. Bullock. 1993. Las abejas nativas de México. Pages 179-226 in T. P. Ramamoorthy, R. Bye, A. Lot, and J. Fa, editors, Diversidad Biológica de México. Orígenes y Distribución. México: Instituto de Biología, UNAM.
• Benitez, H., C. Arizmendi, y L. Marquez. 1999. Mexico: CIPAMEX, CONABIO, FMCN y CCA.
• Challenger, A. 1998. Utilización y conservación de los ecosistemas terrestres de México. Pasado, presente y futuro. México: Conabio, IBUNAM y Agrupación Sierra Madre. ISBN: 9709000020
• CONABIO Workshop, 17-16 September, 1996. Informe de Resultados del Taller de Ecoregionalización para la Conservación de México.
• CONABIO Workshop, Mexico, D.F., November 1997. Ecological and Biogeographical Regionalization of Mexico.
• Gallina, P. T., C. S. Alvarez, R. A. González, y T. S. Gallina. 1991. Aspectos generales sobre la fauna de vertebrados.
• León de la Luz, J.L., H.J. Cancino, y C.L. Arriaga. 1991. Asociaciones fisonómico florísticas y flora.
• Padilla, G., S. Pedrín, y E. Troyo-Diéguez. 1991. Geología.
• Ramamoorthy, T.P., and M. Elliott. 1993. Lamiaceae de México: diversidad, distribución, endemismo y evolución. Pages 501-526 in T.P. Ramamoorthy, R. Bye, A. Lot, and J. Fa, editors, Diversidad Biológica de México. Orígenes y Distribución. México: Instituto de Biología, UNAM.
• Robles Gil, P., G. Ceballos, and F. Eccardi. 1993. Mexican diversity of fauna.
• Rzedowski, J. 1978. Vegetación de Mexico. Editorial Limusa.
• Salinas-Zavala, C., B. R. Coria, and R.E. Díaz. 1991. Climatología y meteorología.

Additional information on this ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage