The Andean mountain range runs the full length of the western side of South America forming the ‘backbone’ of the Southern Cone. To the west, there is a strip of land between the Pacific coast and the mountains. Rainfall decreases from south to north, reaching extreme aridity in northern Chile and southern Peru. East of the Andes there are extensive plains and a ‘plateau’ (the planalto ) that reach the Atlantic coast, forming a mosaic of environments.
Major uninterrupted South American grasslands stretch from southern Brazil through Uruguay and Argentina. There are two main subregions: the campos of southern Brazil and Uruguay (northeast of the Rio de Plata) and the pampas of Argentina (southwest of the Rio de Plata). Between the Andes and the campos is the region known as Chaco - a flat and dry forested landscape - and a gallery tropical forest of the Uruguay and Parana Rivers. In the lower portion of the Southern Cone is the Patagonian region, located between 39° and 55° south latitude. Most of this space is a treeless plateau which is deeply cut by several major rivers with courses flowing in a mainly west to east direction. The Straight of Magallanes separate continental Patagonia from Isla Grande of Tierra del Fuego. This island is the largest of an archipelago in the southern Chilean territory which is composed of hundreds of smaller islands.
The southern Andes are part of the Andean Cordillera. They comprise several subregions: the subtropical forest (a narrow band which extends along the foothills of the eastern mountain ranges), the puna (a high altitude dry plain located between 3400 and 4500 masl), and the valleys and quebradas (located below 3000 masl). In the south, below 38° south latitude, the cordillera is covered by a dense forest of Notophagus (Figure 1).
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