Location and General Description
This Patagonian steppe ecoregion mainly covers the Patagonia region of Argentina from the Atlantic Ocean shore to barely across the border into Chile. The Peninsula Valdés is and outlier of this ecoregion, lying slightly north of the main body. The topography of this ecoregion includes low-lying mountains, plateaus and plains. Soils are variable but generally rocky-sandy and poor in fine materials and organic matter. The climate is very dry and cold with snow during the winter and frosts nearly year-round however annual precipitation does not normally average more than 200 mm. A characteristic of the Patagonian climate is the constant drying wind that blows with great force from the western sector, particularly in the summer months. Winter generally lasts for five months from about June to September with averages of the coldest month between 1° - 3° C below freezing. Elevations range greatly inthis expansive ecoregion from sea level nearer the shores of the Atlantic up to 2000m in the north and about 700 m in the southern extense of the ecoregion due to the Andean areas on the western side (Davis et al. 1997).
In general, the vegetation of this steppe ecoregion is xerophytic and highly adapted for protection against drought, wind and herbivores. The vegetation is considered strongly related to Adean flora by Davis et al. (1997) however the average numbers of endemic species for dominant families is very high with as much as 60% endemism in Leguminosae and 33% in Compositae (Davis et al. 1997). There are three main types of vegetative communities. The most densely covered is semi-desert (45%), shrub-steppe (30%) and grass-steppe (20%). Desert like areas also exist with little to no vegetative cover as well as wet meadow areas which have close to 100% cover.
Semi-desert vegetation has highly adapted features; these dwarf and cushion shrubs are the most widely occuring vegetation type in the ecoregion. Shrubs species of Acantholippia, Benthamiella, Nassauvia and Verbena genera grow in these areas as well as cushion plants of Mulinum spinosum and Brachyclados caespitosus and tuft grasses; the most common being species of Poa and Stipa (Davis et al. 1997; Cabrera 1976). Also abundant are species with heteroblastic growth and small limited-growth branches covered with tight leaves. Junellia tridens and Nassauvia glomerulosa are good examples of this type of plant (Cabrera 1976). Taller woody shrubs indicate a change to shrub steppe communities within the ecoregion. These species of Anarthrophyllum, Berberis, Schinus and Verbena can grow up to 3 meters tall. Valleys and lowlands with higher amounts of water available to vegetation host speacies sedges (Eleocharis), rushes (Juncus), grasses (Agrostis, Hordeum, Polypogon) and in saline areas species of halphytic species (Distichlis, Nitrophila, Puccinellina) (Davis et al.1997).
In this ecoregion we find two endemic species of the genus Prosopis, one species of Larrea and species of the genera Lycium and Schinus. Genera and species endemisms are very frequent in this ecoregion, among them Philipiella, Neobaclea, Xerodraba, Benthamiella, Pantacantha, Saccardophyton, Duseniella, Eriachaenium, and Llepidophylum (Cabrera 1976). There are also numerous endemic species of mammals, birds and amphibians. The National Council for Bird Preservation (NCBP 1992) points to this region as one of the most important in terms of the presence of endemic bird species, and according to the council there are probably ten of such species.
The fauna is very varied in this region. Among birds, we can mention the lesser rhea (Pterocnemia pennata), Patagonian tinamou (Tinamotis ingoufi), grey eagle-buzzard (Geranoaetus melanoleucus), peregrine falcon (Falco peregrinus), band-winged nightjar (Caprimulgus longirostris), lesser canastero (Asthenes pyrrholeuca), Patagonia mockingbird (Mimus patagónicus), Patagonian yellow-finch (Sicalis lebruni) just to name a few. Among mammals we find the mara (Dolichotis patagonum), chinchilla (Lagidium viscacia), Wolffsohn's mountain viscacha (Lagidium wolffsohni), Patagonian weasel (Lyncodon patagonicus), Pategonian opossum (Lestodelphis halli), zorrino patagónico(Conepatus humboldti), puma (Felis concolor), zorro gris chico (Dusicyon griseus), guanaco (Lama guanicoe), etc. Among the reptiles, we can mention lagartijas (Liolaemus fitzingeri and L. kingi), geko patagónico (Homonata Darwin) chelco (Diplolaemus Darwin), among others.
Species in danger of being extinct or vulnerable include the cauquén colorado (Chloephaga rubidiceps), huemul (Hippocamelus bisculus) ñandú petiso (Pterocnemia pennata), macá tobiano (Podiceps gallardoi), mara (Dolichotis patagonum), chinchillón anaranjado (Lagidium wolffsohni), guanaco (Lama guanicoe), zorro gris chico (Dusicyon griseus) and ballena franca (Eubalaena australis) (Chebez 1988; Bertonatti and González 1992; Chebez 1994; García Fernández et al. 1997; Canevari et al. 1998).
The Argentine coasts have high species diversity, including 33 species of cetaceans, 8 species of pinnipeds and more than 450 species of fish in the waters of the Argentine sea (García Fernándz 1994).
Despite the low density of the human population, this ecoregion has been seriously affected due to the fragility of the environment. This ecoregion has many natural reserves. These include the Laguna Blanca National Park (Ramsar), Nahuel Huapi National Park, Perito Moreno National Park, Los Glaciares National Park, Bosques Petrificados Natural Monument, El Payén Provincial Reserve, El Tromen Provincial Reserve, Domuyo Provincial Reserve, Somuncurá Provincial Reserve, Laguna Aleusco Provincial Reserve, Bosques Petrificados José Ormachea Provincial Reserve, Bahía San Julián Provincial Reserve and Península de Valdés Provincial
Types and Severity of Threats
The major problem is desertification due to over-grazing primarily by sheep, damaging the limited plant coverage and exposing the soil to erosion (Soriano and Movia 1986).
In addition, many species of fauna are now in regression due to the tempting prices paid for the skins of chulengos (baby guanacos) and choique [rhea] feathers. There is also pressure on foxes and pumas from hunting and/or poisoning because they are considered a potential threat to flocks.
Justification of Ecoregion Delineation
Within Argentina the delineation’s for the Patagonian Steppe were derived from Daniele and Natenzon (1994), and linework follows their "Estepa Arbustiva Patagónica Arida (arid Patagonian woodland steppe)" region. Other resources consulted include Cabrera (1976) and Morello (1968). The linework for the western portion and within Chile was modified according to UNESCO (1980) and expert opinion at ecoregional priority setting workshops: Valdivia, Chile (April 19-21, 1999), Bariloche, Argentina (October 19 & 20, 1999), and Concepción, Chile (March 24, 2000).
Bertonatti, C. y F. González. Lista de Vertebrados Argentinos Amenazados de Extinción. FVSA. 33pp.
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.
Canevari P., D.E. Blanco, E. Bucher, G. Castro y I. Davidson. 1998. Los Humedales de la Argentina. Clasificación, situación actual, conservación y legislación. Wetlands International. Publicación Nº 46. 208pp.
CIPA 1992. Putting biodiversity on the map, priority areas for global conservation.
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. 604pp
Experts workshops for ecoregional priority setting: Valdivia, Chile (April 19-21, 1999), Bariloche, Argentina (October 19 & 20, 1999), and Concepción, Chile (March 24, 2000)
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, and A.C. Hamilton. 1997. Centres of Plant Diversity. A guide and strategy for their conservation. Volume 3: The Americas. IUCN Publications Unit. Cambridge, U.K.
García Fernández, J.J., R.A. Ojeda, R.M. Fraga, G.B. Díaz, R.J. Baigún. 1997.Mamíferos y aves amenazados de la Argentina. FUCEMA, SAREM, AO del Plata, APN. 221pp.
García Fernández, J. J. 1994. La Biodiversidad de la República Argentina. Informe de Avance para la Administración de Parques Nacionales.
Morello, J. 1968. La vegetación de la República Argentina, No. 10: Las grandes unidades de vegetación y ambiente del Chaco Argentino. Buenos Aires, Argentina.
Soriano. A y C. P. Movia, 1986. Erosión y desertización en la Patagonia. INTERCIENCIA V, 11 (2): 77-83.
UNESCO. 1980. Vegetation map of South America. Map 1:5,000,000. Institut de la Carte Internationale de Tapis Vegetal. Toulouse, France.
Prepared by: Claudia Dellafiore
Reviewed by: In process