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Southern North America: Baja California Peninsula in Mexico

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

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.

  • Scientific Code
    (NA1301)
  • Ecoregion Category
    Nearctic
  • Size
    30,000 square miles
  • Status
    Relatively Stable/Intact
  • Habitats

Description
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 - 1500m), 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 (Padilla et al. 1991). 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 (Salinas-Zavala et al. 1991; Challenger 1998).

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 (León de la Luz et al. 1991). 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
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 (Rzedowsky 1988). In particular, the families Lamiaceae and Fouquieriaceae show considerable radiation within the ecoregion (Ramamoorthy & Elliott 1993).

Endemic mammals include San Quintín Kangaroo Rat (Dipodomys gravipes), and Baja California rock squirrel (Spermophilus atricapillus) (Gallina 1991). A high number of bee species are also endemic to the ecoregion (Ayala 1993). In addition, scorpions and spiders show marked radiation here (Robles Gil et al. 1993). 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 (Challenger 1998). 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 (Castellanos & Mendoza 1991). 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 (Benitez et al. 1999).

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 (Castellanos & Mendoza 1991). 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 covers most of the western half of northern and central Baja Peninsula, Mexico. The ecoregion encompasses a unique and diverse assemblage of species, and with many endemics (see detailed description above). Linework follows INEGI (1996) vegeation classifications, from whivh we lumped the following: "halophitic vegetation", "microphyll desert matorral", "sarcocaulous matorral", "crasicaulous matorral", "sarco-crasicaulous matorral", "spiny matorral", "desert vegetation", and all subsequent agricultural regions within this polygon. Reference was also made to Rzedowski (1978). All lines and ecoregion delineation’s were reviewed at a number of experts workshops (CONABIO 1996 & 1997).

References
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. Base de datos de las AICAS. Mexico: CIPAMEX, CONABIO, FMCN y CCA.

Castellanos, A. V., y S. R. Mendoza. 1991. Aspectos Socioeconómicos. Pages 33-52 in A. Ortega y L. Arriaga, editors, La Reserva de la Biosfera "El Vizcaíno" en la Peninsula de Baja California. México: Centro de Investigaciones Biológicas de Baja California Sur, A.C. Baja California Sur.

Challenger, A. 1998. Utilización y conservación de los ecosistemas terrestres de México. Pasado, presente y futuro. México: Conabio, IBUNAM y Agrupación Sierra Madre.

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. Pages 177-212 in A.Ortega, and L. Arriaga, editors, La Reserva de la Biosfera "El Vizcaíno" en la Peninsula de Baja California. México: Centro de Investigaciones Biológicas de Baja California Sur, A.C. Baja California Sur.

INEGI Map (1996) Comision Nacional Para el Conocimiento y Uso de la Biodiversidad (CONABIO) habitat and land use classification database derived from ground truthed remote sensing data Insitituto Nacional de Estastica, Geografia, e Informática (INEGI). Map at a scale of 1:1,000,000.

León de la Luz, J.L., H.J. Cancino, y C.L. Arriaga. 1991. Asociaciones fisonómico florísticas y flora.Pages 145-176 in Ortega, A. & L. Arriaga, editors, La Reserva de la Biosfera "El Vizcaíno" en la Peninsula de Baja California. Centro de Investigaciones Biológicas de Baja California Sur, A.C. Baja California Sur, México.

Padilla, G., S. Pedrín, y E. Troyo-Diéguez. 1991. Geología. Pages 71-93 in A. Ortega, y L. Arriaga, editors, La Reserva de la Biosfera "El Vizcaíno" en la Peninsula de Baja California México: Centro de Investigaciones Biológicas de Baja California Sur, A.C. Baja California Sur.

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. Cemex & Sierra Madre, México.

Rzedowski, J. 1978. Vegetación de Mexico. Editorial Limusa. Mexico, D.F., Mexico

Salinas-Zavala, C., B. R. Coria, and R.E. Díaz. 1991. Climatología y meteorología. Pages 95-116 in A. Ortega and L. Arriaga, editors, La Reserva de la Biosfera "El Vizcaíno" en la Peninsula de Baja California. Centro de Investigaciones Biológicas de Baja California Sur, A.C. Baja California Sur, México.

Prepared by: Alejandra Valero, Jan Schipper, and Tom Allnutt
Reviewed by: In process

 

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