Acari

Acari National Park (Parque Nacional do Acari) is one of Brazil's newest and largest national parks, covering approximately 2,242,769 hectares of pristine lowland Amazonian rainforest in the state of Amazonas, in the Brazilian Amazon. Located between the Juruena and Aripuanã river basins and extending into the lower Acari River drainage, the park was created in 2013 to fill a critical gap in the protected areas network of the southern Amazon arc of deforestation. The park protects intact terra firme forest, igapó (black water flooded forest), and várzea (white water floodplain forest) ecosystems largely untouched by human activity. Its enormous size and remoteness make it one of the most intact Amazon wilderness areas under federal protection.

Acari National Park's intact Amazon rainforest harbors the full complement of Amazonian megafauna, including jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), giant armadillo (Priodontes maximus), tapir (Tapirus terrestris), white-lipped and collared peccaries, and three species of otters including the giant otter (Pteronura brasiliensis). Monkey diversity is high with spider monkeys (Ateles belzebuth), howler monkeys (Alouatta seniculus), bearded sakis (Chiropotes satanas), and uakaris (Cacajao calvus) documented. The bird checklist likely exceeds 600 species given the park's ecological diversity and connectivity to other Amazon protected areas. Harpy eagles (Harpia harpyja) and crested eagles (Morphnus guianensis) are present. The Acari and tributary river systems support electric eels, arapaima (Arapaima gigas), and a diverse ichthyofauna.

Acari's vegetation is predominantly terra firme (non-flooded) Amazon rainforest with high canopy reaching 30–40 meters, emergent Brazil nut trees (Bertholletia excelsa) and angelim-pedra (Hymenolobium petraeum) exceeding 50 meters. The park's position at the southern Amazon arc encompasses transitional zones between central Amazonia and the cerrado-Amazon boundary to the south. Igapó forests along blackwater rivers are dominated by flood-tolerant species including Aldina heterophylla and Macrolobium acaciifolium, adapted to months of annual inundation. Várzea floodplain forests along whitewater tributaries support higher nutrient soils and distinct florisitic compositions including Cecropia and Pseudobombax. River margins support canarana (Paspalum repens) grass beds and aquatic macrophyte communities in slower channels. Epiphytic diversity throughout the canopy is extremely high.

Acari National Park sits on the stable Precambrian crystalline basement of the Guiana and Central Brazilian shields, largely mantled by deep lateritic soils developed under intense tropical weathering over tens of millions of years. The Acari River and its tributaries drain over Archean and Proterozoic gneisses, granites, and metasedimentary rocks exposed in scattered outcrops and rapids. The river systems carry the typically dark, acidic blackwater characteristic of river systems draining the nutrient-poor shield geology — the tea-colored water reflects dissolved organic acids from decomposing rainforest vegetation. Some river sections expose granitic inselbergs (exposed rock domes). The park's geology is not well characterized scientifically given its remoteness; detailed geological mapping has not been conducted in much of the park interior.

Acari falls within the humid equatorial climate zone (Köppen Af) with high rainfall distributed year-round, averaging 2,000–2,500 mm annually with no pronounced dry season. Mean temperatures remain relatively stable year-round at 25–27°C. Relative humidity consistently exceeds 85% throughout the year. The park lies in a region where annual dry seasons are shorter than in the southern Amazon arc, resulting in fewer tree-mortality events associated with drought stress. River levels in the Acari and Juruena systems fluctuate significantly between flood season (January–May) and low water (July–October), driving the alternation between flooded igapó forest and exposed riverine habitats. Climate change models project increasing drought frequency and severity in southern Amazonia, creating long-term risks for this ecosystem.

The Acari region has been inhabited by indigenous peoples for millennia, including the Munduruku nation whose territories extend through the Juruena and Tapajós basins. More recently, the Piripkura — one of Brazil's few remaining uncontacted or recently-contacted indigenous peoples — inhabit areas near the park boundary. The extreme remoteness of the Acari basin meant minimal colonial penetration compared to Amazon river corridors. The rubber boom of the late 19th and early 20th centuries brought limited extraction activities to the larger rivers but never penetrated deeply into the Acari headwaters. Since the 1970s, intensifying deforestation on the southern Amazon arc — driven by cattle ranching and soy agriculture — has approached the park's southern boundary, making the region's protection increasingly urgent.

Acari National Park was established on December 5, 2013, by Decree No. 8.186, during the government of President Dilma Rousseff. Its creation was part of Brazil's strategy to expand protected areas in the most threatened zone of the Amazon — the southern arc of deforestation — ahead of expected infrastructure expansion including the BR-319 highway rehabilitation linking Manaus to Porto Velho. The park was created alongside several other protected areas in the region as part of a coordinated conservation expansion. Management by ICMBio (Instituto Chico Mendes de Conservação da Biodiversidade) is limited by the park's extreme remoteness and lack of road access. Scientific expeditions to characterize the park's biodiversity have been limited; a 2017 ICMBio rapid biological assessment documented dozens of species new to science.

Acari National Park is not currently accessible to general tourists due to its extreme remoteness and absence of visitor infrastructure. Access requires helicopter or multi-day river expedition via the Juruena, Aripuanã, or Acari rivers. The park is effectively a wilderness reserve with no established visitor programs. Scientific expeditions have documented pristine blackwater rivers with crystal-clear visibility, extensive igapó flooded forests, and abundant wildlife — jaguar tracks, arapaima surfacing in river pools, and giant otter groups are reported regularly during expedition surveys. The park's sheer scale and pristine condition represent a conservation attraction of global significance. Future ecotourism development is unlikely in the near term given management resource constraints and access challenges.

No public visitor infrastructure exists within Acari National Park. ICMBio maintains minimal presence through mobile surveillance operations using boats along park boundary rivers. Scientific researchers seeking access must apply through ICMBio's research authorization system (SISBIO) and arrange their own logistics (boat, fuel, provisions for multi-week expeditions). The nearest substantial town is Apuí (Amazonas state), approximately 400 km from the park boundary by road from Manaus (950 km total from Manaus via the AM-174/BR-230). There are no commercial tour operators currently running trips into the park interior. The park's inaccessibility is, in many respects, its greatest conservation asset — maintaining the wilderness conditions that protect its extraordinary biodiversity.

Acari National Park faces severe conservation threats despite its legal protection. Illegal gold mining (garimpo) has expanded dramatically in the Amazon since 2018, with illegal airstrips and camps penetrating deep into the southern Amazon. The BR-319 highway rehabilitation — which would connect Manaus to Porto Velho through currently roadless Amazon — is the most serious infrastructure threat, as experience with other Amazon highways shows forest clearing extending 50–100 km from new roads. Illegal logging and land grabbing in the park's southern buffer zones continue despite federal prohibition. ICMBio's surveillance capacity is severely limited by resource shortages. The park is part of the Juruena-Sucunduri-Acari conservation mosaic — a landscape-scale approach to Amazon protection that depends on active international support through bilateral conservation agreements and carbon credit mechanisms.