Location and General Description
The Argentine Monte ecoregion is restricted to the pre-Andean region of western Argentina ranging from Salta (24º 35’S) to Chubut (44º 20’S) provinces. It extends from 62º 54’S on the Atlantic coast to 69º 50’S, then from see level to 2800 m elevation. It is a warm scrub desert extending between the Puna, Patagonia and Chaco ecoregions. The climate is temperate-arid with very little rainfall (between 80 and 250 millimeters per year). The northern and central regions of the Monte receive rains in summer but in the south is colder and rainfall is distributed throughout the year (Morello 1958; Cabrera 1976).
The dominant vegetative formation of this ecoregion is scrublands, that at times can be very open. The steppe is formed by resinous evergreen bushes dominated by representatives of the Zygophyllaceae family, such as species from the genera Larrea (jarillas), Bulnesia (retamos) and Plectocarpa (mancapotrillos). They can be found together with Montea aphyla (mata sebo), and Bougainvillea spinosa (monte negro) and Prosopis sp (algarrobo). Other types of vegetation are cactus scrub, xerophilous open woodland, rock associations, psammophilous associations, and halophilous associations (Morello 1958). Cactaceae (Trichocereus and Cereus) and Bromeliacea (Dyckia, Deuterochonia, Tillandsia) are more abundant in the northern part of this ecoregion. There are many herbaceous species that appear after the rain, such as Portulaca grandiflora (flor de seda), wild irises and lilies and some grasses (Cabrera and Willink 1980). Mesquite trees (Prosopis sp) form gallery forests on the river borders or can be found were subterranean water is available (Morello 1958).
The "jarillal" is the most characteristic community of the Monte ecoregion developing in pockets on plains of sandy or rocky-sandy soil. Larrea cuneifolia colonizes the hotter and drier parts of the Monte, while L. divaricata can only grow as riparian species and L. nitida grows in cold environments as well in the slopes of the Andes (Ezcurra et al. 1991). In addition, there are different edaphic communities such as the woods of Prosopis scrubs of Baccharis salicifolia (chilca) and Tessaria dodonaefolia (pájaro bobo) in humid places, Atriplex in clayish soils and Suaeda divaricata and Allenrolfea vaginata in salty soils (Cabrera and Willink 1980; Morello 1958).
The Monte ecoregion was an important setting for the evolution of temperate biota of the continent. Endemism is a consequence of evolution in isolated areas since the Oligocene. This ecoregion has several endemic species of flora and fauna. Among the plants, we can mention Romorinoa girolae (chica), Gomprhena colosacana var andersonii from the Sierra de las Quijadas National Park and species with limited distribution in Argentina like verdolaga (Halophytum ameghinoi), a fleshy grass that grows in bogs (Morello 1958). The insect fauna is quite well known from the northern part of the Monte where there are a high proportion of endemic genera (10%) and out of species (35%) belong to different families (Roig-Juñent et al. 2001).
The most characteristic mammal fauna of the Monte are the edentates quirquincho chico or piche llorón (Chaetophractus vellerosus), pichiciego (Chlamyphorus tuncatus), carnivores such as puma (Felis concolor), zorro gris chico (Pseudalopex griseus), zorrino chico (Conepatus castaneus), huroncito or hurón chico (Lyncodon patagonicus), the ungulate guanaco (Lama guanicoe), and the rodents cuis chico (Microcavia australis), mara (Dolichotis sp). The red viscacha rat (Tympanoctomys barrerae) and the pichiciego (Chlamyphorus truncatus) are mammals endemic to this biome; they are also listed as vulnerable according to IUCN categories. The critically endangered rodent Ctenomys validus (tuco-tuco de Guaymallén) and vulnerable rodent species such as Octomys mimax, Andalgalomys roigi and Salinomys delicatus, the mara (Dolichotis patagonum) and in some parts of the ecoregion the guanaco (Lama guanicoe) can all be found in this ecoregion (Diaz and Ojeda 2000).
Birds include the copetona or martineta común (Eudromia elegans), monterita canela (Poospiza ornata), inambú pálido or petiso (Nothrura darwinii), loro barranquero (Cyanoliseus patagonus), and others. Threatened birds are Falco peregrinus (halcón peregrino) and Harpyhaliaetus coronatus.(águila coronada). There are also threatened reptiles species that inhabit the Monte such as the terrestrial turtle (Chelonoidis chilensis) and lampalagua (Boa constrictor) (Chebez 1988; Bertonatti and González 1992; Chebez 1994; García Fernández et al. 1997). In general, we find various species of reptiles like the lizard or iguana colorada (Tupinambis rufescens) and ophidia such as the falsa yarará (Pseusotomodon trigonatus), yarará ñata (Bothrops ammodytoides), lampalagua (Boa constrictor occidentalis) and falsa coral (Lystrophis semininctus). Among the amphibians, we can mention Pleurodema nebulosa.
In this ecoregion, the most important wetland is the system of lagoons in Guanacache and Rosario in the Mendoza province; a Ramsar site that is home to an interesting diversity of aquatic birds such as Euxenura maguari, Chauna torquata, Plegadis chini, Phoenicopterus chilensis and ducks of the genus Anas. We also find migratory birds like plovers and sandpipers (Sosa 1999).
Human populations preferred to occupy oases in valleys and other locations close to rivers that make irrigation possible. This is why some sections of the ecoregion were intensively altered but others were not. The forest also underwent significant depredation as man occupied patches and used wood for vineyards, mining, furniture making, construction and as fuel. Overgrazing and deforestation has caused erosion that affected 58 million hectares of the ecoregion (Roig-Juñent et al. 2001).
There are national and provincial protected areas in the ecoregion that represent less than 2% of the surface area. They are placed within the central and southern parts of the ecoregion. They include Los Cardones National Park (Salta province), Sierra de las Quijadas National Park (San Luis province), Talampaya National Park (La Rioja province), Valle Fértil Provincial Reserve (partially within the ecoregion), San Guillermo provincial reserve, Ichigualasto Provincial Park (San Juan province), Telteca Provincial Reserve, Nacuñán Provincial and Biosphere Reserve, Laguna de Llancanelo Provincial Reserve, Divisadero Largo Provincial Reserve (Mendoza province), Lihué Calel Provincial and National Park, La Humada Provincial Reserve, La Reforma Provincial Reserve, Salitral Levalle Provincial Reserve (La Pampa province), Cinco Chañares Provincial Reserve, Complejo Islote Lobos Provincial Reserve, Caleta de los Loros Provincial Reserve (Rio Negro province), El Mangrullo Provincial Reserve (Neuquén province), and Península de Valdés provincial Reserve (Chubut province). Even with this extensive list of protected areas the northern parts of the Monte ecoregion is not protected nor are large tracts of land needed by many species to compete their life cycles.
Types and Severity of Threats
The Monte, as well as in the Chaco and Patagonia lowland, is experiencing seriously damaging effects due to human activities, especially overgrazing by goats, sheep and cattle; clear cutting for fuel; and land clearing for agriculture, mining and oil exploration (Ojeda et al. 1998). The deforestation and selective extraction of hardwood and clear cutting of mesquite forests began at the late 19th and early 20th centuries and continues today. Anthropogenic activities during the past 150 years have led to pronounced desertification, disruption of habitats and changes in the biodiversity and geographic ranges of many species (Roig 1991).
Justification of Ecoregion Delineation
The delineation’s for the Argentine Monte were derived from Daniele and Natenzon (1994), and linework follows their classification of "Monte y Cardonales de la Prepuna (woodlands and thistle of the prepuna)" region. Other resources consulted include Cabrera (1976) and Morello (1968).
Bertonatti, C. Y F. González. Lista de Vertebrados Argentinos Amenazados de Extinción. FVSA. 33pp.
Cabrera, A.L. y A. Willink. 1980. Biogeografía de América Latina. O.E.A. Serie Monográfica Nº 4. Washington D.C.
Cabrera, A. L. 1976. Regiones Fitogeográficas de Argentina. Enciclopedia Argentina de Agricultura y Jardinería. Tomo II. Fascículo I. Editorial ACME S.A.C.I. 85pp.
Cabrera, A. L. 1976. Regiones fitogeográficas Argentinas. Enciclopedia Argentina de Agricultura y Jardinería, Second Edition, Vol. II, Buenos Aires, Argentina.
Chebez, J. C. 1988. El deterioro de la Fauna. Capítulo VI del libro El deterioro del Ambiente en la Argentina (suelo, agua, vegetación, fauna). FECIC. 497pp
Chebez, J.C. 1994. Los que se van. Albatros. 604 pp
Daniele, C., and C. Natenzon. 1994. Regiones Naturales de la Argentina. Draft map. Argentina National Parks Department, Buenos Aires, Argentina.
Diaz, G.B. and R.A. Ojeda, editors, 2000. Libro Rojo de los Mamíferos amenazados de Argentina. Sociedad Argentina para el Estudio de los Mamíferos, SAREM. 106 pp.
Ezcurra, E., C. Montaña y S. Arizaga. 1991. Architecture, light interception, and distribution of Larrea species in the Monte desert, Argentina. Ecology 72: 23-34.
García Fernández, J.J., R.A. Ojeda, R.M. Fraga, G.B. Díaz, and R.J. Baigún. 1997.Mamíferos y aves amenazados de la Argentina. FUCEMA, SAREM, AO del Plata, APN. 221pp.
Morello, J. 1958. La provincia fitogeográfica del monte. Opera Lilloana 2: 1-1555.
Morello, J. 1968. La vegetación de la República Argentina, No. 10: Las grandes unidades de vegetación y ambiente del Chaco Argentino. Buenos Aires, Argentina.
Ojeda, RA, Campos, C.M. Gonnet, J.M. Borghi, C.E. and Roig, V.G. 1998. The MaB Reserve of Ñacuñán, Argentina: its role in understanding the Monte Desert Biome. Journal of Arid Environments 39:299-313.
Ringuelet, R. 1961. Rasgos fundametales de la zoogeografía de la Argentina. Physis (Buenos Airtes) 22:151-188.
Roig, V.G. 1991. Desertification and distribution of mammals in the southern cone in South America. In: Mares, M.A.; Schmidly, D. (eds), Latin America Mammalogy. History, biodiversity, and conservation, pp 239-279. Norman: University of Oklahoma Press. 468 pp.
Roig-Juñent, S., G. Flores, S. Claver, G. Debandi and A. Marvaldi. 2001. Monte desert (Argentina): insect biodiversity and natural areas. Journal of Arid Environments 47(1): 77-94.
Sosa, H. 1999. Informe Taller Lagunas de Guanacache, Lavalle - Mendoza, Argentina. Oficina de Medio Ambiente de la Municipalidad de Lavalle.
Prepared by: Claudia Dellafiore
Reviewed by: In process