Description
Location and General Description
The Patagonian grasslands are located at the bottom tip of South America. The region extends from the Santa Cruz Province in Argentina to the Tierra del Fuego in Chile and Argentina. The ecoregion also includes the Islas Malvinas or Falkland Islands on the Atlantic Ocean. The Strait of Magellan divides the ecoregion in two. The northern section is part of mainland South America and the southern section constitutes the Tierra del Fuego Island. The Patagonian grasslands show a relief of low mountains, mesas and plains. The soils are rich with high concentrations of fine materials and have a lot of organic material. The climate is cold and humid with 200- 300 mm of rain per year and an average temperature below 8 ºC.
The dominant vegetation of this ecoregion consists of grass-steppe interspersed with shrubs (Cabrera, 1976). Some of the plant species include the coirón blanco (Festuca pallescens), senecio (Senecio patagonicus) and Palntago maritime. Atriplex reichei and Lepidophyllum cupressiforme (a stocky shrub with alternating scaly leaves) are found in salty soils near the sea. Common genera in the region include Adesmia, Anarthrophyllum Berberis, Chuquiraga, Lycium, Mulinum, Schinus and Verbena (Villamil 1997). In the Tierra del Fuego the steppe's dominant vegetation is coirón (Festuca gracillima), a perennial grass 30 – 70 cm high, with thin, stiff, pleated leaves. Other grasses include Poa atropidiformis, Trisetum sp., and Hordeum comosum. The bottom of the valleys and plains are dominated by cebada silvestre (Hordeum comosum), with Alopecurus antarticus, Phleum conmutatus, Poa pratensis, Agrosti sp. (Cabrera 1976).
Biodiversity Features
Wetlands are of great importance in this ecoregion including the following: marsh and lagoons of Tero, marsh of Rio Pelque, Lago Argentino, lagoons of Puerto Bandera, Lake Viedma, lagoons of the Meseta del Tobiana, lagoons Escarchados. Areas with a high importance in the coastal zone include Río Santa Cruz, Monte León, Río Coig, Ría Gallegos, Cabo Vígenes, Bahía San Sebastián, Río Grande, Península Mitre, Canal Beagle and Isla of the Estados (Canevari et al. 1998).
The fauna is very diversified in this region. Some of the mammals include the Patagonian Mara (Dolichotis patagonum), the Southern Viscacha (Lagidium viscacia), the Wolffsohn's Viscacha (Lagidium wolffsohni), the Patagonian Weasel (Lyncodon patagonicusi), the Humboldt's Hog-nosed Skunk (Conepatus humboldti), the puma (Felis concolor), the Falkland Island wolf (Dusicyon australis), the Guanaco (Lama guanicoe). There are numerous birds in the ecoregion, some of them are the Lesser rhea (Pterocnemia pennata), the Patagonian tinamou (Tinamotis ingoufi), the Black-chested buzzard-eagle (Geranoaetus melanoleucus), the Peregrine (Falco peregrinus), the Band-winged nightjar (Caprimulgus longirostris), the Patagonian mockingbird (Mimus patagónicus), and the Patagonian yellowfinch (Sicalis lebruni).
The Patagonian grasslands and the southern part of the Patagonian steppe ecoregion have various endemic birds. These birds inhabit various types of habitat from freshwater lakes to coastal water and rocky shores. Endemic birds frequently found in the Santa Cruz Province and north of the Straits of Magellan include the hooded grebe (Podiceps gallardoi), Magellanic plover (Pluvianellus socialis), chocolate-vented tyrant (Neoxolmis rufiventris), canary-winged finch (Melanodera melanodera), short-billed miner (Geositta antarctica), ruddy-headed goose (Chloephaga rubidiceps), and striated caracara (Phalcoboenus australis), which is found also south of the Straits of Magellan (Stattersfield et al. 1998). The blackish cinclodes (Cinclodes antarcticus) is found in the Tierra del Fuego Island. Endemic birds of the Falkland Islands are the Falkland steamerduck (Tachyeres brachypterus) and the Cobb’s wren (Troglodytes cobbi). The Islands are also very important for various seabirds including the Gentoo penguins (Pygoscelis papua) (Stattersfield et al. 1998).
Threatened species in the ecoregion include the cauqué colorado (Chloephaga rubidiceps), the ñandú petiso (Pterocnemia pennata), the Patagonian Mara (Dolichotis patagonum), the guanaco (Lama guanicoe), the zorro gris chico (Dusicyon griseus), and the lobo de dos pelos (Aretocephalus australis) (Chebez 1988; Bertonatti and González 1992; Chebez 1994; García Fernández et al 1997).
Current Status
The human population in the ecoregion is low, but the area has been affected by grazing livestock and introduced herbivores (Dinerstein et al 1995). The natural grassland, in particular tussock grass, has been destroyed, and endemic birds in the area rely directly or indirectly on this grass (Stattersfield et al. 1998). There are not many protected areas in this ecoregion; some of them are Dicky Private Reserve, the Reserva Costa Atlántica Tierra del Fuego, and Magallanes National Reserve.
Types and Severity of Threats
Desertification is the most serious threat to this ecoregion. Grazing of cattle and introduced herbivores deteriorates the scarce vegetation cover, leaving the soil exposed to processes of erosion (Soriano and Movia 1988; Dinerstein et al 1995). The destruction of the natural habitat has severely affected the avifauna in the area, especially endemic species. Three species are of particular concern: Great grebe (Podiceps gallardoi), with few than 5,000 individuals remaining, Ruddy-headed goose (Chloephaga rubidiceps), with a serious decline in population numbers, and Striated caracara (Phalcoboenus australis), whose numbers have declined due to hunting (Stattersfield et al. 1998).
Justification of Ecoregion Delineation
The delineation’s for the Patagonian Grasslands were derived from Daniele and Natenzon (1994), and linework follows their classification of "Pastizales Australes (austral grasslands)" region. Other resources consulted include Cabrera (1976) and Morello (1968).
References
Bertonatti, C., y F. González. Lista de Vertebrados Argentinos Amenazados de Extinción. FVSA, Buenos Aires, Argentina.
Cabrera, A.L. 1976. Regiones Fitogeográficas de Argentina. Enciclopedia Argentina de Agricultura y Jardinería. Tomo II. Fascículo I. Editorial ACME S.A.C.I., Buenos Aires Argentina
Canevari P., D.E. Blanco, E. Bucher, G. Castro, e I. Davidson. 1998. Los Humedales de la Argentina. Clasificación, situación actual, conservación y legislación. Humedales para las Americas, Buenos Aires, Argentina.
Chebez, J.C. 1988. El deterioro de la Fauna. En El deterioro del Ambiente en la Argentina (suelo, agua, vegetación, fauna). Fundación para la Educación, la Ciencia y la Cultura, Buenos Aires, Argentina.
Daniele, C., and C. Natenzon. 1994. Regiones Naturales de la Argentina. Draft map. Argentina National Parks Department, Buenos Aires, Argentina.
Dinerstein, E., D.M. Olson, D.J. Graham, A.V. Webster, S.A. Primm, M.P. Bookbinder, y G. Ledec. 1995. Una evaluación del estado de conservación de las ecoregiones terrestres de América Latina y el Caribe. Fondo Mundial para la Naturaleza, Banco Mundial Washington, D.C.
García Fernández, J.J., R.A. Ojeda, R.M. Fraga, G.B. Díaz, y R.J. Baigún. 1997. Mamíferos y aves amenazados de la Argentina. FUCEMA, SAREM, AO del Plata, APN, Buenos Aires, Argentina.
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
Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. (1998). A global directory of Endemic Bird Areas. BirdLife Conservation Series. BirdLife International, Cambridge, U.K.
Villamil, Carlos B. 1997. Patagonia. S.D. Davis, V.H. Heywood, O. Herrera-MacBryde, J. Villa-Lobos, and A.C. Hamilton, editors. Centres of plant diversity: A guide and strategy for their conservation, Vol. 3 The America. IUCN, WWF, Oxford, U.K.
Prepared by: Claudia Dellafiore
Reviewed by: In process