Gran Chaco - Flora and Fauna

Flora and Fauna

The Gran Chaco has some of the highest temperatures on the continent.

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, sub-canopy, shrub layer and herbaceous layer. There are ecosystems such as riverine forests, wetlands, savannas, and cactus stands as well.

At higher elevations of the eastern zone of the Humid/Sub-humid Chaco there are transitional mature forests from the wet forests of Southern Brazil. These woodlands are dominated by canopy trees such as Tabebuia impetiginosa 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 like Schinus fasciculatus. These lower areas lack lianas but have abundant epiphytic species like Tillandsia. The river systems that flow through the area, such as the Rio Paraguay and Rio Parana allow for seasonally flooded semi evergreen gallery forests that hold riparian species such as Tessaria integrifolia and Salix humboltiana. Other seasonally flooded ecosystems of this area include palm dominated (Copernicia alba) savannas with a bunch grass dominated herbaceous layer.

To the west, in the Semi-Arid/Arid Chaco, there are medium sized forests consisting of Aspidospermum quebracho-blanco and Schinopsis quebracho with a slightly shorter subcanopy made up of several species from the Fabaceae family as well as several arboreal cacti species that distinguish this area of the Chaco. There is a scrub-like shrub and herbaceous layer. On sandy soils, the thick woodlands turn into savannas where the aforementioned species prevail as well as species like Jacaranda mimosifolia. The giant Stetsonia coryne, found throughout the western Semi-Arid/Arid region becomes very conspicuous in these sandy savannas. There are various upland systems of plant associations that occur throughout the Gran Chaco. The Highlands of the Argentenian Chaco are made up of, on the dry, sunny side (up to 1800m), Schinopsis haenkeana woodlands. The cooler side of the uplands hosts Zanthoxylum coco (locally referred to as Fagara coco) and Schinus molleoides (locally referred to as Lithrea molleoides) as the predominant species. Other notable species include Bougainvillea stipitata, and several spp. from Fabaceae. The Paraguyan uplands have other woodland slope ecosystems, notably, those dominated by Anadenanthera colubrina on moist slopes. Both of these upland systems, as well as a lot of other areas in the Gran Chaco are rich with endemism.

Faunal diversity in the Gran Chaco is high as well. Animals regularly associated with tropical and subtropical forests are often found throughout the eastern humid chaco including jaguars, howler monkeys, peccaries, deer, and tapirs. Edentate species, including anteaters and armadillos are readily seen here as well. Being home to at least ten species, armadillos are at their peak diversity in the Argentenian Chaco. Included in the species present are both the Nine-banded Armadillo (Dasypus novemcinctus) whose range extends north to the southern US, and the Southern Three-banded Armadillo (Tolypeutes matacus). The Pink Fairy Armadillo (Chlamyphrous truncates), is found nowhere else in the world. The Giant Armadillo (Priodontes maximus), while not found in the eastern humid Chaco, can be seen in the drier arid Chaco of the west. Some other notable endemics of the region include the San Luis Tuco-tuco (Ctenomys pontifex). This small rodent is only found in the Argentenian Chaco. All of 60 species of Ctenomys are endemic to the continent of South America. The Chacoan Peccary (Catagonus wagneri), locally known as tauga, is the largest of the three peccary species found in the area. This species was thought to be extinct by scientists until 1975, when it was recorded by Dr. Ralph Wetzel.

Due to the climatic regime of the Gran Chaco, herptopfauna are restricted to moist refugium in various places throughout the chaco. Rotting logs, debris piles, old housing settlement, wells, and seasonal farm ponds are examples of such refugia. The Black-legged Serieman (Chunga burmeisteri), Blue-crowned Parakeet (Aratinga acuticadauta), Picui Ground Dove (Columbina picui), Guira Cuckoo (Guira guira), Little Thornbird (Phacellodomus sibilatrix) and Many-colored Chaco Finch (Saltaitricula multicolor) are notable of the 409 bird species that are resident or breed in the Gran Chaco. 252 of these chaco species are endemic to South America.

In September 1995, the Kaa Iya del Gran Chaco National Park was established in an area of the Chaco in Bolivia. It is administered and was established solely by the indigenous peoples, including the Izoceño Guaraní, the Ayoreode, and the Chiquitano.