Humid Chaco

The Humid Chaco ecoregion occupies the lowlands of the Paraná River, covering portions of northeastern Argentina, the center of Paraguay, and small areas in southwestern Brazil. Asuncion, Paraguay's capital, lies within the ecoregion.

The topography is generally flat or gently rising, and the soils are primarily fine alluvium deposited by the area's rivers. The natural vegetation is a mosaic of grasslands, palm savanna, and forest.

Grasslands and savannas are generally found on higher ground and forests along streams and river floodplains. Bogs form seasonally or year-round over impermeable soil layers.

The Humid Chaco is bounded west by the Dry Chaco, the Alto Paraná Atlantic forests in the east, and the Cerrado grasslands to the northeast.

The climate is tropical, becoming subtropical towards the south. The average annual temperature ranges from 23 °C (73.4 °F) along the Paraguay border in the north to 18 °C (64.4 °F) in Argentina in the south.

Average annual rainfall generally decreases towards the west and ranges from 1,300 mm (50 in) in the wetter eastern portions to 750 mm (30 in) in the west near the transition to the Dry Chaco. Rainfall is highest in summer (January to April) and lowest in winter (June to August).

Flora and Fauna

The forests comprise hardwood trees: willow-leaf red and white quebracho. Other notable trees are the pink trumpet and silk floss.

Lower areas often flood, forming bogs containing the trees black carob, spiny hackberry, Jerusalem thorn, and white carob. In addition, palm savannas, including the palm Copernicia alba, are typical.

The grasslands of the Humid Chaco are quite varied: Elionurus muticus is dominant in forests, Sorghastrum agrostoides in flooded soils, and Panicum prionites in ravine and depression bottoms without permanent water.

The diverse flora in this ecoregion naturally supports high faunal diversity. Mammals of note include the vulnerable white-lipped peccary, giant anteater, and marsh deer.

Other large mammals include the black howler monkey, Azara's night monkey, maned wolf, collared peccary, capybara, pampas deer, cougar, and jaguar.

Restricted range birds that inhabit this ecoregion, among others, include the vulnerable chestnut seedeater and the endangered marsh seedeater. Other birds common to the area include savannah hawk, pale-crested woodpecker, undulated tinamou, and greater rhea.

Reptiles dominate the aquatic environments, including spectacled caiman, broad-snouted caiman, black spine-neck swamp turtle, and yellow anaconda.

Protection Status

Historically, cattle ranching and forest exploitation have profoundly reduced the original vegetation of the ecoregion through grazing, logging, and burning for agriculture.

Protected areas include Chaco National Park, Río Pilcomayo National Park, Mburucuyá National Park in Argentina, and Ypoá National Park in Paraguay.

The Iberá Wetlands, located in the southeast of the ecoregion adjacent to the Southern Cone Mesopotamian savanna, are protected by Argentina's Iberá Provincial Reserve and Iberá National Park.

_{Map depicting the location of the Humid Chaco (in purple)}