Anavilhanas National Park

Anavilhanas National Park, located in Amazonas, Brazil, encompasses a large archipelago in the Río Negro, approximately 70 km (43 mi) upstream from Manaus. Here, the river becomes almost 30 km (18 mi) wide during the wet season. It is part of the Central Amazon Conservation Complex, a World Heritage Site.

The park protects the environment of the Anavilhanas River archipelago in the Río Negro, one of the largest in the world, and its forest formations. Created in 1981 as a strictly protected ecological station, it was reclassified to the more open (but still protected) National Park status in 2008.

The Anavilhanas National Park is administered by ICMBio (Chico Mendes Institute for Biodiversity Conservation). Within the archipelago are two floating and one terrestrial base to support inspection and research. These structures are located near Lago do Prato, the Baipendi River and at the mouth of the Apuaú River.

The fluvial part of the park, 60% of the total, has more than 400 islands. It is about 130 km (81 mi) long and, on average, 20 km (12 mi) wide, with a total area of 350,470 ha (866,000 acres). The islands comprise approximately 100,000 ha (247,000 acres), and the balance is protected riverside forests.

The National Park is bounded north and east by the Rio Negro Left Bank Environmental Protection Area, a 611,008 ha (1,509,830 acres) sustainable use conservation area created in 1995.

The fluvial section extends to the west shore of the Río Negro, which is mainly protected by the Rio Negro Right Bank Environmental Protection Area and the Rio Negro Sustainable Development Reserve.

The terrain ranges from 50 - 150 m (160 - 490 ft) above sea level. The average annual rainfall is 2,100 mm (83 in). Temperatures range from 23 - 34 °C (73 - 93 °F). The park contains a variety of forest types and river and lake ecosystems.

The water level fluctuation during high tide in the wet season and low tide in the dry season is between 8 and 12 m (26 and 40 ft). The islands and most vegetation are flooded during high tide, creating the igapós (blackwater-flooded forests). In the dry season, beaches of different sizes are formed.

Protected species include margay (Leopardus wiedii), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), giant armadillo (Priodontes maximus), giant otter (Pteronura brasiliensis), Amazonian manatee (Trichechus inunguis) and Amazon river dolphin (Inia geoffrensis).

Anavilhanas Archipelago

The Anavilhanas archipelago was created by the buildup of sediments and debris resulting from the erosion of the Guyana Highlands that was brought down by the Rio Branco and deposited here in the dark acidic waters of the Río Negro in a spectacular delta-like formation.

Anavilhanas is the world's second-largest fluvial archipelago (the first is Mariuá, nearby), which describes the aquatic mosaic of floating vegetation. A "fluvial archipelago" sits amid a river or stream and refers to the landmass and deposits created by the action of the water.

The Anavilhanas Archipelago hosts incredible biodiversity and distinct ecosystems that stand out amongst the already rare habitat of the Amazon Rainforest. It is part of the Central Amazon Conservation Complex, the largest protected area in the Amazon Basin.

The Anavilhanas archipelago covers 350,000 ha (866,000 acres) and consists of about 400 islands, 60 lakes, dozens of paranás (river channels), and furos (narrow paths that cross the igapós).

The islands vary in size according to the river's water level. The water level varies by up to 10 m (33 ft) between ebb and flood periods, with high water from October to March and low water from April to September.

Due to the constant movement of the water, the islands are in a continuous process of change as sedimentation and erosion occur. Therefore, with the different seasons, the islands appear to "move," look noticeably different, and offer other activities based on the season.