Location and General Description
The Arid Chaco ecoregion lies west of the Córdoba montane savannas ecoregion, and south of the Chaco ecoregion. These ecoregions form the Gran Chaco area described by Davis (1997). The northern, southern, western and eastern boundaries of this ecoregion terminate approximately at the 280 and 330 west latitudes and 680 and 660 south longitudes, respectively (Anon. 1980). Most scientists agree that the Chaco formed during Pleistocene post-glacial fluctuations, from an arid to humid to semi arid environment, as initially proposed by Lüders (1961). The climate is dry, with an annual rainfall of 650-350 mm, and an average temperature of 28°C-12°C. Both of these figures included some data from the semi arid Chaco. The rivers in the region are ephemeral (Davis et al. 1997).
As part of the Gran Chaco center of plant diversity, this ecoregion has a unique flora. Plants more commonly associated with this ecoregion include Aspidosperma quebracho-blanco, Prosopis flexuosa, Ziziphus mistol, abd Opuntia spp. (Fernandez et al. 1997; Davis et al. 1997). Herbaceous species include Bromelia serra, B. hieronymi and Deinacanthon urbanianum. Aside from savanna areas there are areas with saline soils where shrubby steppe species such as Heterostachys serra, B. hieronymi and Deinacanthon urbanianum. Understory species include Caesalpinia paraguarensis, Cercidium australis, Jodina rhombifolia, Ruprechtia triflora and Castella cocinea (Davis et al. 1997).
The arid Chaco and the sorrounding ecoregions contain a high diversity of flora, especially for the genus Prosopis. Twenty of the 44 species of Prosopis are native to the Gran Chaco (Davis et al. 1997). The area is also rich in faunal diversity. Armadillos, with at least ten species, reach their peak diversity in the Argentine Chaco (Zuleta and Bolkovic 1994). Two mammals that are endemic to this region are the pink fairy armadillo (Chlamyphrous truncatus), and the tuco-tuco, Ctenomys pontifex (Olrog and Lucero 1980). An isolated population of pampas deer (Ozotoceros bezoarcticus) may occur here as well (Olrog and Lucero 1980). This is the only region where the lesser maras (Pediolagus salinicola) and Patagonian maras (Dolichotis patagonum) are apparently sympatric (Olrog and Lucero 1980). Moreover, several broadly distributed tropical species reach the southern terminus of their range in this region, such as the crab-eating raccoon (Procyon cancrivorous) (Olrog and Lucero 1980).
The black-legged serieman (Chunga burmeisteri), blue-crowned parakeet (Aratinga acuticadauta), Picui ground dove (Columbina picui), Guira cuckoo (Guira guira), little thornbird (Phacellodomus sibilatrix) and many-colored Chaco finch (Saltaitricula multicolor) make up a large part of the unique avifauna represented in this ecoregion (Narosky and Yzurieta 1989; Fernandez et al. 1997).
Much of the Arid Chaco is in various stages of alteration due to over-grazing and human overpopulation (Roig 1991). By the early 1990s only 10% of the original forested land remained. (Rogi 1991). The region has some protected areas including Reserva Chancani in Cordoba (Fernandez et al. 1997), and Cerro Colorado, a Resource Reserve and World Heritage Site. Davis et al. (1997) recommend the creation of a Nature Reserve of 20,000 km2 to protect a very high diversity of Prosopis species in the region.
Types and Severity of Threats
The area has been severely affected by logging and livestock grazing. Desertification, caused by human development, is indeed the principle threat to this ecoregion. Paved road development provides easy access to remote sites to hunt game and alter pristine regions through agrarian development. Perhaps the main threat to the few pristine regions of the Chaco is increased development.
Justification of Ecoregion Delineation
These arid shrublands of north-central Argentina amongst the Córdoba Mountains, east of the foothills of the Andes – interspersed among montane savannas. Linework follows Daniele and Natenzon (1994) who classify this region as "forests and shrublands of the arid chaco". This ecoregion hosts a number of endemic species. Reference was also made to other literature which helped distinguish this region (Cabrerea 1976 and Morello 1968).
Anon. 1980. Time-Hammond World Atlas. Hammond, Inc., Maplewood, N.J.
Cabrera, A. L. 1976. Regiones fitogeográficas Argentinas. Enciclopedia Argentina de Agricultura y Jardinería, Second Edition, Vol. II, Buenos Aires, Argentina
Caziani, S. M., M. Mosqueira, G. Monasterio-Gonzo, E. Derlindati, y J. Merler. 1997. Informe sobres las especies de Argentina. Pages 492-502 in S. D. Strahl, S. Beaujon, D. M. Brooks, A. J. Begazo, G. Sedaghatkish, and F. Olmos, editors, The Cracidae: Their biology and conservation. Hancock House, WA
Daniele, C., and C. Natenzon. 1994. Regiones Naturales de la Argentina. Draft map. Argentina National Parks Department, Buenos Aires, Argentina.
Davis, S. D., V. H. Heywood, O. Herrera-MacBryde, J. Villa-Lobos and A. C. Hamilton. 1997. Centres of plant diversity: A guide and strategy for their conservation. WWF and IUCN, Oxford, U.K.
Fernandez, E., E. V. Alvarez, and M. B. Martella. 1997. Variacion estacional de la abundancia pobliacional del calancate comun (Aratinga acuticaudata) en la Reserva Chancani, Cordoba, Argentina. Hornero 14: 259-262.
Lüders, R. 1961. Bodenbildungen im Chaco Boreal von Paraguay als Zeugen des spät- und postglazialen Klimaablaufs. Geologisches Jahrbuch 78:603-608.
Morello, J. 1968. La vegetación de la República Argentina, No. 10: Las grandes unidades de vegetación y ambiente del Chaco Argentino. Buenos Aires, Argentina.
Narosky, T., and D. Yzurieta. 1989. Birds of Argentina and Uruguay. Vazquez Mazzini Buenos Aires, Argentina.
Olrog, C. C., and M. M. Lucero. 1980. Guiá de los Mamiferos Argentinos. Fundación Miguel Lill, Tucuman, Argentina.
Olson, D., E. Dinerstein, P. Hedao, S. Walters, T. Allnutt, C. Loucks, Y. Kura, K. Kassem, A. Webster, and M. Bookbinder. 2000. Terrestrial Ecoregions of the Neotropical Realm. Conservation Science Program, WWF-US, Washington D.C.
Roig, V. G. 1991. Desertification and distribution of mammals in the Southern Cone of South America. Pages 239-279 in M.A. Mares and D.J. Schmidly, editors, Latin American Mammalogy: History, Biodiversity and Conservation. Univ. Okla. Press, Norman.
Zuleta, G., and M. L. Bolkovic. 1994. Conservation ecology of armadillos in the Chaco region of Argentina. Edentata 1: 16-17.
Prepared by: Dr. Dan Brooks
Reviewed by: In process