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Southern North America: Southern Baja California in western Mexico

Located at the southern most part of the Baja Peninsula, this diverse landscape of mountains, valleys, and plateaus is covered with a variety of xeric vegetation. Plants and animals of this region evolved independently before joining the Baja Peninsula. A dry, arid climate supports a number fauna and species of, about ten percent which are endemic. This region supports a number of endemic birds and is listed as an Endemic Bird Area. Established as a Protected Natural Area (PNA), much of the ecoregion remains intact.

  • Scientific Code
    (NT1314)
  • Ecoregion Category
    Neotropical
  • Size
    1,500 square miles
  • Status
    Vulnerable
  • Habitats

Description
Location and General Description
This ecoregion is contained in a larger area known as the Cape Region, and constitutes the southernmost part of the Baja California peninsula. The area originated in the Miocene as an isolated portion of land prior to joining the peninsula in its present position, and thus is considered an "island" of vegetation (Arriaga & Ortega 1988, Challenger 1998). The region is composed of a vast complex of granitic mountains, valleys, canyons, and plateaus. The ecoregion occupies the plateaus between the coast and the lower limits of the dry forests, which begin around 250m. Precipitation is about 400mm annually. Some elements of the dry forest are present in this community, but xeric elements are dominant and include Opuntia cholla, Bursera microphylla, Lysiloma divaricata, Stenocereus thuberii, Cnidoscolus angustidens, Yucca sp., and Ferocactus spp. Herbaceous elements are present and include Plantago linearis, Bouteloua hirsuta, and Commelina coelestis.

Biodiversity Features
The past and present isolation of Sierra de la Laguna from the rest of the peninsula has played a major role in producing an extraordinary array of unique species. Although the ecoregion has not been studied intensively (Rodríguez-Estrella 1988, Gallina-Tessaro and González 1988, León de la Luz et al. 1988), it is widely recognized that it houses 31 of 48 of the reptile species for the Cape Region (Alvarez-Cárdenas et al. 1988). Almost a third of the region’s recorded species of collembola and spiders (30 of 138 species) have been found in this ecoregion (Jiménez 1988, Vázquez 1988). In general, more than ten percent of animal and plant species found at Sierra de la Laguna are endemic. All of the ecoregion is contained within the extensive Baja California Endemic Bird Area (Stattersfield et al. 1998). The isolation of this region has also contributed to the scarcity of predators, and to the poor competitive ability of some animals (Arriaga & Ortega 1988). Rodents and lagomorphs are virtually absent in this region, favoring certain species of animals that would otherwise be subject to competition. This is the case with Melanerpes formicivorus, for example (Rodríguez-Estrella 1988). The Cape Region has also served as a natural refuge for species migrating from neighboring regions undergoing long-term geological change (Arriaga & Ortega 1988).

Current Status
The Mexican state of Baja California Sur, which includes this ecoregion, contains the highest proportion of intact xeric scrub of any Mexican state (Flores-Villela & Gerez 1994). Large areas of habitat remain intact, as the topography makes this ecoregion difficult to exploit (Arriaga 1988). In June 1994, the region was established as a Protected Natural Area (PNA) with pine-oak forests and subtropical dry forest as the key areas for protection. The fragile nature of this region requires legal protection over a long period, in order to prevent it from disturbances caused by human overpopulation and exploitation of forest resources for livestock.

Types and Severity of Threats
Native villagers often killed wild species (mostly predators) that are considered as threats to their domestic animals (Ortega & Arriaga 1988). If this continues, it could alter the natural processes maintaining biodiversity in the area. Although human disturbance in the Sierra de la Laguna has been kept to a minimum, any uncontrolled perturbation to this fragile ecosystem could create an imbalance. This would ultimately cause the disappearance of an extraordinary array of evolutionary phenomena that has produced such a unique vegetation assemblage in the middle of an enormous desert.

Justification of Ecoregion Delineation
This xeric scrub ecoregion is limited to the southern tip of the Baja Peninsula in Mexico, and is thus isolated from other similar habitats. Delineation’s for this ecoregion follow INEGI (1996), from which we lumped the following vegetation classifications: "sarcocaulous matorral", "crasicaulous matorral", and portions of "agricultural landuse". Reference was also made to Rzedowski (1978), and reviews and revisions to the linework were done by expert opinion at several ecoregional priority setting workshops (CONABIO 1996 and 1997).

References
Alvarez-Cárdenas, S., P. Gallina-Tessaro, y A. González. 1988. Herpetofauna. Pages 167-184 in L. Arriaga, y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

Arriaga, L. 1988. Importancia ecológica de las perturbaciones exógenas en un bosque de pino-encino. Pages 115-132 in L. Arriaga, y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

Arriaga, L., y A. Ortega, 1988. Características generales. Pages 15-26 in L. Arriaga y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de 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.

Flores-Villela, O., y P. Gerez. 1994. Biodiversidad y conservación en México: Vertebrados, vegetación y uso de suelo. México: CONABIO & UNAM..

Gallina-Tessaro, P., y A. González. 1988. Mastofauna. Pages 209-228 in L. Arriaga y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de 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.

Jiménez, M.L. 1988. Aspectos ecológicos de las arañas. Pages 149-166 in L. Arriaga, y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

León de la Luz, J.L., R. Domínguez, y R. Coria. 1988. Aspectos florísticos. Pages 83-144 in L. Arriaga, y A. Ortega, editor, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

Rodríguez-Estrella, R. 1988. Avifauna. Pages 185-208 in L. Arriaga y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

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

Stattersfield, A.J., M.J. Crosby, A.J. Long and D.C. Wege. 1998. Endemic Bird Areas of the World: Priorities for Biodiversity Conservation. Birdlife Conservation. Series No. 7., Birdlife International, Cambridge, UK.

Vázquez, M.M. 1988. Fauna colembológica de hojarasca y suelo. Pages 133-148 in L. Arriaga y A. Ortega, editors, La Sierra de la Laguna de Baja California Sur. México: Centro de Investigaciones Biológicas de Baja California Sur.

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

 

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