Dry Chaco Ecoregion: Gran Chaco

The Dry Chaco ecoregion, or Gran Chaco, or simply Chaco, is a sparsely populated, hot, semi-arid lowland alluvial plain of the Río de la Plata basin.

It is divided among eastern Bolivia, western Paraguay, northern Argentina, and a portion of the Brazilian states of Mato Grosso and Mato Grosso do Sul, connected with the Pantanal region. The region is about 647,500 sq km (250,000 sq mi), though estimates differ.

More than twice as big as the state of California, the Dry Chaco ecoregion contains South America's second-largest forest, behind only the Amazon Rainforest.

The Chaco region is primarily a lowland alluvial sedimentary plain bounded west by the Andes Mountains, the Paraguay River in the northeast and the Paraná River in the southeast.

The two permanent rivers found in the Chaco, the Pilcomayo and the Bermejo (Teuco), flow southeastward across the plain from their Andean headwaters to the Paraguay River and demarcate the three main regional divisions of the region in Paraguay and Argentina:

• Chaco Boreal: north of the Pilcomayo River

• Chaco Austral: south of the Bermejo River

• Chaco Central: between the two rivers

The Dry Chaco ecoregion is subject to climates ranging from tropical in the north to warm-temperate in the south. Most of the region, however, is subtropical.

Average temperatures vary from 60 - 85 °F (16 - 29 °C), with an average relative humidity of 50 - 75%. The average annual precipitation is 865 mm (34 in).

Flora and Fauna

Chaco vegetation is highly varied, complex, and adapted to grow under arid conditions. From dry thorn forests and cactus stands to palm savannas that flood in the wet season, the region has diverse landscapes and high biodiversity, containing approximately:

• 3,400 species of plants

• 500 species of birds

• 150 species of mammals

• 220 species of reptiles and amphibians

Protection Status

The Gran Chaco is one of South America's last agricultural frontiers. Very sparsely populated and lacking good all-weather roads and basic infrastructure, it has long been too remote for crop planting (the central Chaco's Mennonite colonies are a notable exception).

While advancements in agriculture can improve infrastructure and employment for the region, the loss of virgin forest/habitat is proving to be substantial.

From 2010 to 2012, Argentina, Paraguay and Bolivia (the three countries that share most of the Chaco) lost native vegetation at an average rate of more than an acre per minute. By 2030, the region is projected to lose millions of additional acres of native vegetation.

_{Map depicting the approximate location of the Gran Chaco region}