Acari

Acari National Park (Parque Nacional do Acari) is one of Brazil's newest and largest national parks, covering 896,410 hectares (approximately 8,964 km²) of lowland Amazon rainforest in the state of Amazonas. ^[1] Created on 11 May 2016 by presidential decree, it lies within the Madeira River basin, protected from the watersheds of the Acari, Camaiú, Sucunduri, and Abacaxis rivers and their tributaries, in the southern portion of the Amazon that faces intense deforestation pressure. ^[1] The park covers parts of the municipalities of Apuí, Borba, and Novo Aripuanã in Amazonas. It protects extensive tracts of terra firme forest along with flooded forest ecosystems, and it forms part of a mosaic of protected areas established to shield this region ahead of expanding infrastructure. Managed by ICMBio, Acari is among the most intact and remote wilderness areas under federal protection in Brazil, safeguarding the watersheds of its namesake and neighboring rivers.

Acari's intact forests support the full range of Amazonian wildlife. Large mammals include jaguar, giant anteater, giant armadillo, lowland tapir, and collared and white-lipped peccaries, while the park's rivers shelter giant otters and other aquatic species. Primate diversity is high, with spider monkeys, howler monkeys, sakis, and uakaris among the groups expected across its varied forest habitats. The remoteness and ecological diversity of the park suggest a very rich avifauna, with harpy and crested eagles among the raptors present, alongside numerous parrots, macaws, and forest passerines. The Acari and its tributaries carry a diverse fish fauna adapted to blackwater and mixed-water conditions. Because the park has seen little scientific survey, its documented species lists remain incomplete relative to its likely biodiversity.

The park's vegetation is predominantly terra firme (non-flooded) Amazon rainforest, with a tall closed canopy and emergent trees such as Brazil nut rising above the general forest. Its position toward the southern Amazon places it near the transition between central Amazonia and the drier vegetation to the south, adding floristic variety. Along blackwater rivers, igapó forests are dominated by species tolerant of months of seasonal flooding, while whitewater tributaries support várzea floodplain forest on richer alluvial soils, giving distinct plant communities. River margins carry aquatic and semi-aquatic vegetation in slower channels. Epiphytic orchids, bromeliads, and other plants contribute to a high overall diversity in the canopy, characteristic of intact lowland Amazon forest that has experienced little human disturbance.

Acari sits on the stable Precambrian basement of the Brazilian Shield, largely mantled by deep, heavily weathered soils formed under intense tropical conditions over long geological timescales. The Acari River and its tributaries drain across ancient crystalline and metasedimentary rocks that are exposed here and there as outcrops and rapids. Rivers draining this nutrient-poor shield country tend to carry dark, acidic blackwater, stained tea-colored by dissolved organic matter from decaying forest vegetation. The overall relief is low and gently undulating, typical of the lowland Amazon interior. Because of the park's remoteness and the very limited fieldwork conducted within it, its geology has not been mapped in detail, and much of the interior remains geologically little known.

The park lies within the humid equatorial climate of the southern Amazon, with high rainfall and warm temperatures throughout the year. Annual precipitation is on the order of 2,000 to 2,500 millimeters, and while rainfall is abundant, this part of the Amazon has a more defined lower-rainfall period than areas farther west. Mean temperatures remain stable in the mid-20s Celsius, and relative humidity stays high year-round. River levels in the Acari system rise and fall markedly between the flood season and the low-water months, driving the seasonal alternation between inundated igapó forest and exposed riverbanks. Climate models project increasing drought frequency across southern Amazonia, posing long-term risks to this ecosystem.

The Acari region falls within the ancestral territories of Amazonian indigenous peoples, including groups of the Munduruku and neighboring nations whose lands extend through the surrounding basins. The wider area is significant for the presence of isolated or recently contacted indigenous peoples, whose protection is closely tied to the integrity of these remote forests. The park's inaccessibility historically limited colonial and commercial penetration, so that the rubber-boom extraction of the late 19th and early 20th centuries touched the larger rivers but never fully reached the Acari headwaters. From the 1970s onward, however, deforestation driven by cattle ranching and agriculture advanced across the southern Amazon toward this region, making the protection of the Acari basin increasingly pressing.

Acari National Park was established on 11 May 2016 by presidential decree, as part of a coordinated effort to expand protected areas in the most threatened zone of the Amazon ahead of anticipated infrastructure expansion, including plans to upgrade highways linking the region to the rest of the country. ^[1] The park protects the biodiversity of the Acari, Camaiú, Sucunduri, and Abacaxis rivers and their tributaries, and it was created alongside other units to form a landscape-scale conservation mosaic in southern Amazonas. Management by ICMBio is constrained by the park's extreme remoteness and lack of road access, so protection relies heavily on the area's inaccessibility together with mobile enforcement operations along boundary rivers.

Acari National Park is not currently open to general tourism, owing to its extreme remoteness and the absence of any visitor infrastructure. Reaching the park requires multi-day river expeditions along the Aripuanã, Sucunduri, or Acari rivers, or aircraft, and it functions in practice as a wilderness reserve rather than a destination. Its principal significance is the scale and near-pristine condition of its forests, blackwater rivers, and flooded igapó, which are of global conservation importance. Scientific expeditions have begun to document this biodiversity, but organized visitor programs do not exist and are unlikely to develop in the near term given the logistical challenges and the priorities of managing such a remote unit.

There is no public visitor infrastructure within Acari National Park. ICMBio maintains only a minimal presence, largely through mobile surveillance along boundary rivers. Researchers seeking access must obtain authorization through Brazil's scientific research permitting system and arrange their own logistics for what are inevitably long and expensive journeys. The nearest towns lie at the edges of the region, with the municipality of Apuí in Amazonas among the closer settlements reachable via the regional highway network from larger cities. No commercial operators run trips into the park interior. In practice, the park's very inaccessibility is one of its greatest conservation assets, helping to preserve the wilderness conditions that sustain its exceptional biodiversity.

Despite its legal protection, Acari National Park faces significant conservation pressures. Illegal gold mining has expanded across the Amazon, with clandestine airstrips and camps penetrating remote areas, and illegal logging and land grabbing continue in the park's buffer zones. Proposed and ongoing infrastructure projects, particularly highway improvements that would open currently roadless forest, represent the most serious long-term threat by making the region more accessible to deforestation. ICMBio's capacity to patrol such a vast and remote area is limited by scarce resources. The park is part of a broader conservation mosaic in southern Amazonas designed to protect the landscape at scale, an approach that depends on sustained national commitment and international support to remain effective.