The Iberá Wetlands (Esteros del Iberá, from the Guaraní for "bright water") are a rain-fed maze of marshes, shallow lagoons and floating vegetation islands in the centre and north of Corrientes province, northeastern Argentina, between the Paraná and Uruguay rivers. Estimates of their size run from about 12,000 km² to 20,000 km² depending on where the blurred edge is drawn, which makes Iberá the largest wetland in Argentina and, by most accounts, second in South America only to the Pantanal. About 13,000 km² sits inside the Iberá Provincial Reserve, created in 1983 and the largest protected area in the country; 24,500 hectares were listed as a Ramsar Wetland of International Importance in 2002, and Iberá National Park was created by Argentina's Congress on 5 December 2018.
The simplest way to understand Iberá is to cross it the way its water does: in from the high ground beside the Paraná in the northeast, through the chain of lagoons at its heart, and out again to the southwest, where two small rivers carry the overflow away to two different great rivers.
Ituzaingó and the Yacyretá Reservoir on the Northern Rim
The journey starts on the Paraná at Ituzaingó, a Corrientes town on the Argentina–Paraguay border. A few kilometres away the river is blocked by the Yacyretá Dam, an 808-metre-long hydroelectric dam whose 20 turbines first ran together on 7 July 1998. Its reservoir rises 21 metres above the river's old level and covers about 1,600 km², and from its completion in 1994 the rising water level affected the region and drowned part of the neighbouring ecosystem. Corrientes responded with provincial decree 1577/94, which regulated conservation units in the dam's area of influence and drew funding from the binational entity that runs Yacyretá.
Geologists have long suspected that this corner of the province explains the wetland itself. A basalt fault runs diagonally across Corrientes and meets the Paraná about 90 km downstream of Posadas. One theory holds that the basalt wall once turned the river southeast, through the lowland that now holds the esteros, until erosion opened a path through the rocky rapids at Yacyretá–Apipé. The soils support the idea: layers of river sand and silt sit on a clay floor that stops water from draining downward, so rain that falls on Iberá stays at the surface.
Concepción, Loreto and the Old Northern Edge
Heading south and west from the river, the land drops into the depression locally called La Crespa. Here the wetland's northeastern and northwestern edges have no clear boundary; ranch pasture simply becomes wetter until it becomes marsh. Settlements on this side are old. Concepción, known in full as Concepción Yaguareté-Corá, dates from the colonial era, and the Jesuit reductions of the 17th and 18th centuries occupied land next to the esteros, though the missionaries treated the flooded interior as uninhabitable. For the next two centuries the marshes had no permanent villages and served as a refuge for outlaws and a hunting ground for the trappers called mariscadores.
The first scientific description came from the French naturalist Alcide d'Orbigny, who crossed the area in the late 1820s for the Muséum d'Histoire Naturelle in Paris and recorded it in his seven-volume Voyage dans l'Amérique méridionale. A century later, in the 1930s, Argentina's new National Parks Administration proposed an Iberá national park to Congress. That bill and two later ones failed, partly because Corrientes did not want to give up so much of its territory. Tourism eventually arrived from the private side: in 1983 the Estancia San Juan Poriahú near Loreto opened the first lodge in the area built for ecotourism and birdwatching.
Laguna Iberá, Laguna Luna and Colonia Carlos Pellegrini
The centre of the journey is the chain of permanent lagoons along the wetland's main axis. The largest are Laguna Iberá, which gives the system its name, and Laguna Luna. Fernández, Galarza, Medina, Paraná and Trin each exceed 15 km². None is deep: the average does not pass about 3 metres even in floods, and the annual rise and fall is only about a metre. The floor of the whole basin lies at an average of roughly 65 metres above sea level, and the gradient is so slight that water creeps southwest through the reeds rather than flowing.
On a peninsula pushing into Laguna Iberá stands Colonia Carlos Pellegrini, founded in 1927 and home to 683 people at the 2001 census. It is the usual base for visitors and is linked by road to Mercedes in the southwest. From its jetties boats head out among the embalsados, the floating mats for which Iberá is known. They begin as tangles of water hyacinth (camalote) and other floating plants; wind-blown soil gathers on the roots until some mats can bear a person's weight. Because these islands drift and thicken, the line between water and land keeps moving, and finding your way by eye, on foot or by boat, is notoriously hard.
The lagoons around the village are where most of Iberá's wildlife is seen. The provincial reserve records about 350 bird species. Four mammals have been declared provincial natural monuments: the marsh deer, the pampas deer, the maned wolf and the neotropical otter. Both of Argentina's caimans live here, the yacare caiman (yacaré negro) and the broad-snouted caiman (yacaré overo), along with large numbers of capybara, the world's largest rodent. The climate is subtropical, with very hot, humid summers, occasional winter frosts and rainfall estimated at roughly 1,200 to 1,700 mm a year, most of it in spring and autumn.
Iberá National Park and the Rewilded Ranches, 1999–2022
West of the central lagoons the journey crosses the land that has changed most in the last 25 years. From 1999 the Conservation Land Trust, a foundation set up by the American conservationists Doug and Kristine Tompkins, bought cattle ranches inside the reserve. It removed most of the cattle, took down interior fences and stopped the practice of burning pasture for fodder. In 2015 the trust donated about 150,000 hectares, much of it flooded, to the Argentine state, and on 5 December 2018 Congress created Iberá National Park from those lands, covering about 1,381 km² in the centre of the reserve. Corrientes had already set aside 5,530 km² of public land in the southwest as Iberá Provincial Park in 2009. Together the national and provincial parks form the largest protected area in Argentina.
In 2007 Tompkins Conservation began reintroducing animals that hunting and ranching had wiped out of Corrientes during the 20th century. The work, now run by Rewilding Argentina, has brought back the giant anteater, collared peccary, South American tapir, pampas deer, bare-faced curassow, red-legged seriema, giant otter and ocelot. Red-and-green macaws, thought to have disappeared from Argentina by the 1960s, were imported from captive flocks in Britain in 2015, and the first pair was released in February 2019. Jaguars, gone from the area since the first half of the 20th century, were bred in large enclosures where cubs learned to hunt. In January 2022 the first male was released, bringing the number of jaguars set free in the park to eight.
The same month showed how fragile the recovery is. In January and February 2022, after about two and a half years of drought, wildfires burned nearly 60% of the national park. Lightning started at least one, but many spread from neighbouring ranches where pasture is still managed with fire. The grasslands are adapted to burning, but patches of forest that rarely burn were also lost, and with the lagoons low, many animals had nowhere to escape. Rewilding Argentina staff rescued many of the reintroduced animals.
Mercedes and the Payubré Rise to the South
Leaving Carlos Pellegrini by road, the route runs southwest to Mercedes, a city of 40,667 people at the 2010 census and the nearest town of any size, 275 km from the provincial capital, Corrientes. The land here starts to change. South of the esteros the low hills of the province's southern half mark the wetland's only firm boundary, and the Payubré plateau acts as a natural dam, holding back Iberá's water on its way to the Paraná. Land in the reserve that is outside the two parks is mostly private cattle ranches, and the road from Mercedes is the main way in for visitors bound for the central lagoons.
Out by the Corriente and the Miriñay
The water ends its journey through two outlets. The larger is the Corriente River, which leaves the Itatí lagoon in the centre-north of the province, drains a basin of about 13,000 km² and flows southwest across the bañados (seasonally flooded marshes) until it reaches the floodplain of the Paraná near Esquina. The smaller is the Miriñay, which rises in its own esteros southeast of Iberá and runs about 200 km south to the Uruguay River near Monte Caseros. Iberá therefore feeds both great rivers of the Argentine Mesopotamia.
That double drainage nearly ended the wetland in the 1970s. A provincial development plan proposed a canal near San Miguel to flood the esteros with Paraná water and turn them into an inland lake, then send that water down the Miriñay to raise output at the Salto Grande hydroelectric dam on the Uruguay. It was never built, but the hunting of the same decade did real damage: by the early 1980s the yacare caiman, hunted for leather, along with the jaguar and the deer were scarce or gone. That decline is what pushed Corrientes to pass Law 3771 on 15 April 1983 and create the provincial reserve, the start of the protection that the national park completed 35 years later.
Iberá is one part of the much larger Paraná–Paraguay wetland system that links the Pantanal to the Paraná Delta, so it is worth comparing its rain-fed lagoons with the river-fed floodplains of the Pantanal wetlands in Brazil, Bolivia and Paraguay. The river that frames its northern edge is traced from source to estuary in our Paraná River guide, and the province's place among Argentina's other landscapes is set out in our overview of the geography of Argentina.