Gran Chaco
The Gran Chaco, is a vast semiarid lowland region in central South America, spanning over one million square kilometers across eastern Bolivia, western Paraguay, northern Argentina, and parts of Brazil. It forms part of the Río de la Plata basin.
Gran Chaco features a mix of tropical and subtropical dry broadleaf forests, thorn scrub, savannas, wetlands, and palm groves, making it the continent’s second-largest forested ecoregion and a region of high ecological diversity.
The Gran Chaco is home to more than 3,400 plant species, around 500 bird species, 150 mammals, and more than 200 reptiles and amphibians, including jaguars, giant armadillos, peccaries, and maned wolves. Its forests and soils also store carbon and regulate water cycles, playing a significant role in climate moderation.
The region has been sparsely inhabited for centuries by Indigenous peoples, including the Wichí, Qom, Pilagá, Guaraní, and Ayoreo, among others. Today, it supports approximately 4 million people, many of whom maintain traditional livelihoods closely tied to the land.
In recent decades, the Gran Chaco has experienced extensive environmental degradation. Expanding cattle ranching, soybean farming, illegal logging, and fire-driven deforestation have led to the large-scale conversion of native forests. Argentina alone lost about seven million hectares of forest between 1998 and 2023, much of it in the Chaco. As of 2024, deforestation has continued to intensify.
Conservation efforts include the establishment of protected areas such as Kaa-Iya National Park in Bolivia, sustainable land-use initiatives, Indigenous-led stewardship programs, and local alliances for climate resilience. However, governance challenges, weak enforcement, and legal gaps continue to limit progress.
Toponymy
The name Chaco comes from the Quechua word chaqu meaning "hunting land", an indigenous language from the Andes and highlands of South America, and comes probably from the rich variety of animal life present throughout the entire region.Geography
The Gran Chaco is about 647,500km2 in size, though estimates differ. It is located west of the Paraguay River and east of the Andes, and is mostly an alluvial sedimentary plain shared among Paraguay, Bolivia, and Argentina. It stretches from about 17 to 33°S latitude and between 65 and 60°W longitude, though estimates differ.Historically, the Chaco has been divided in three main parts: the Chaco Austral or Southern Chaco, south of the Bermejo River and inside Argentinian territory, blending into the Pampa region in its southernmost end; the Chaco Central or Central Chaco between the Bermejo and the Pilcomayo River to the north, also now in Argentinian territory; and the Chaco Boreal or Northern Chaco, north of the Pilcomayo up to the Brazilian Pantanal, inside Paraguayan territory and sharing some area with Bolivia.
Locals sometimes divide it today by the political borders, giving rise to the terms Argentinian Chaco, Paraguayan Chaco, and Bolivian Chaco.
The Chaco Boreal may be divided in two: closer to the mountains in the west, the Alto Chaco, sometimes known as Chaco Seco, is very dry and sparsely vegetated. To the east, less arid conditions combined with favorable soil characteristics permit a seasonally dry higher-growth thorn tree forest, and further east still higher rainfall combined with improperly drained lowland soils result in a somewhat swampy plain called the Bajo Chaco, sometimes known as Chaco Húmedo. It has a more open savanna vegetation consisting of palm trees, quebracho trees, and tropical high-grass areas, with a wealth of insects. The landscape is mostly flat and slopes at a 0.004-degree gradient to the east. This area is also one of the distinct physiographic provinces of the Parana-Paraguay Plain division.
The areas more hospitable to development are along the Paraguay, Bermejo, and Pilcomayo Rivers. It is a great source of timber and tannin, which is derived from the native quebracho tree. Special tannin factories have been constructed there. The wood of the palo santo from the Central Chaco is the source of oil of guaiac. Paraguay also cultivates mate in the lower part of the Chaco.
Large tracts of the central and northern Chaco have high soil fertility, sandy alluvial soils with elevated levels of phosphorus, and a topography that is favorable for agricultural development. Other aspects are challenging for farming: a semiarid to semihumid climate with a six-month dry season and sufficient fresh groundwater restricted to roughly one-third of the region, two-thirds being without groundwater or with groundwater of high salinity. Soils are generally erosion-prone once the forest has been cleared. In the central and northern Paraguay Chaco, occasional dust storms have caused major topsoil loss.
History
The Chaco was occupied by nomadic peoples, notably the various groups making up the Guaycuru, who resisted Spanish control of the Chaco, often with success, from the 16th until the early 20th centuries.Prior to national independence of the nations that compose the Chaco, the entire area was a separate colonial region named by the Spaniards as Chiquitos.
The Gran Chaco had been a disputed territory since 1810. Officially, it was supposed to be part of Argentina, Bolivia, and Paraguay, although a bigger land portion west of the Paraguay River had belonged to Paraguay since its independence. Argentina claimed territories north of the Bermejo River until Paraguay's defeat in the War of the Triple Alliance in 1870 established its current border with Argentina.
Over the next few decades, Bolivia began to push the natives out and settle in the Gran Chaco, while Paraguay ignored it. Bolivia sought the Paraguay River for shipping oil out into the sea, and Paraguay claimed ownership of the land. This became the backdrop to the Gran Chaco War between Paraguay and Bolivia over supposed oil in the Chaco Boreal. Eventually, Argentine Foreign Minister Carlos Saavedra Lamas mediated a ceasefire and subsequent treaty signed in 1938, which gave Paraguay three-quarters of the Chaco Boreal and gave Bolivia a corridor to the Paraguay River with the ability to use the Puerto Casado and the right to construct their own port. No oil was found in the region until 2012 when Paraguayan President Federico Franco announced the discovery of oil in the area of the Pirity river.
Image:Aerial view of Km 75 Ruins.jpg|thumb|left|220px|Road construction in the deep Gran Chaco during the 1960s
Mennonites immigrated into the Paraguayan part of the region from Canada in the 1920s; more came from the USSR in the 1930s and immediately following World War II. These immigrants created some of the largest and most prosperous municipalities in the deep Gran Chaco.
The region is home to over 9 million people, divided about evenly among Argentina, Bolivia, and Brazil, and including around 100,000 in Paraguay. The area remains relatively underdeveloped, In the 1960s, the Paraguayan authorities constructed the Trans-Chaco Highway and the Argentine National Highway Directorate, National Routes 16 and 81, in an effort to encourage access and development. All three highways extend about from east to west and are now completely paved, as is a network of nine Brazilian highways in Mato Grosso do Sul state.
Flora
The Gran Chaco has some of the highest temperatures on the continent.It has high biodiversity, containing around 3,400 plant species, 500 birds, 150 mammals, and 220 reptiles and amphibians.
The floral characteristics of the Gran Chaco are varied given the large geographical span of the region. The dominant vegetative structure is xerophytic deciduous forests with multiple layers, including a canopy, subcanopy, shrub layer, and herbaceous layer. Ecosystems include riverine forests, wetlands, savannas, and cactus stands, as well.
At higher elevations of the eastern zone of the Humid Chaco, mature forests transition from the wet forests of southern Brazil. These woodlands are dominated by canopy trees such as Handroanthus impetiginosus and characterized by frequent lianas and epiphytes. This declines to seasonally flooded forests, at lower elevations, that are dominated by Schinopsis spp., a common plains tree genus often harvested for its tannin content and dense wood. The understory comprises bromeliad and cactus species, as well as hardy shrubs such as Schinus fasciculata. These lower areas lack lianas, but have abundant epiphytic species such as Tillandsia. The river systems that flow through the area, such as the Rio Paraguay and Rio Parana, allow for seasonally flooded semievergreen gallery forests that hold riparian species such as Tessaria integrifolia and Salix humboldtiana. Other seasonally flooded ecosystems of this area include palm-dominated savannas with a bunch grass-dominated herbaceous layer.
To the west, in the Semiarid/Arid Chaco, medium-sized forests consists of white quebracho and red quebracho with a slightly shorter subcanopy made up of several species from the family Fabaceae, as well as several arboreal cacti species that distinguish this area of the Chaco. There is a scrub-like shrub and herbaceous understory. On sandy soils, the thick woodlands turn into savannas where the aforementioned species prevail, as well as species such as Jacaranda mimosifolia. The giant Stetsonia coryne, found throughout the western Semiarid/Arid region becomes very conspicuous in these sandy savannas. Various upland systems of plant associations occur throughout the Gran Chaco. The Highlands of the Argentinian Chaco are made up of, on the dry, sunny side, Schinopsis haenkeana woodlands. The cooler side of the uplands hosts Zanthoxylum coco and Schinus molleoides as the predominant species. Other notable species include Bougainvillea stipitata, and several species from the Fabaceae. The Paraguayan uplands have other woodland slope ecosystems, notably, those dominated by Anadenanthera colubrina on moist slopes. Both of these upland systems, as well as numerous other Gran Chaco areas, are rich with endemism.