Anavilhanas Ecological Station
The Anavilhanas Ecological Station (ESEC) is made up of 350,018 hectares and is located in the north-eastern Amazonas state, on the lower Rio Negro (Black River), the main tributary of the Amazon River. It is one of the world’s largest fluvial archipelagoes, with approximately 400 islands and hundreds of lakes, rivers, swamps and sandbanks, all rich in animal and plant life.
The Ecological Station is constituted by a 100,000-hectare archipelago, of hundreds of elongated islands and canals within the Rio Negro riverbed, covered by inundated forests. Included are 250,000 hectares of unflooded forests on the riversides.
The archipelago was created by accumulation of sediments resulting from the erosion of the Guyana Hills (Rio Branco) and intense flocculation with organic matter from the black acidic waters of Rio Negro. This process explains the islands peculiar composition (silt and caolinite), form and disposition. Flocculation started in two parallel banks, meeting downstream and trapping sediment to form a delta-like area. Large basins and lakes between the islands, up to 20 metres deep, are temporarily isolated during the dry season. Some channels are permanently open and have a faster stream. Islands and channels location is changing over time, due to the seasonal water cycles, periodic floods, acidity and debit fluctuations.
Islands and river margins are mostly covered by a low, dense, periodically flooded rainforest (igapo forests). Its vegetation shows specific adaptation to long periods of floods, such as the aerial root system, specialized reproduction cycle and fast growth. Palm trees are locally abundant.
Unflooded forests are higher, more complex, with dense canopy, isolated elevated trees and dense subwood vegetation. There are two types: lowland and sub-mountain. Lowland forests occur between 5 and 100 metres altitude, and sub-mountain higher, up to 600 metres.
Forested shrub-lands (Campinarana arborea) are specialized ecosystems occurring on some islands of the archipelago and on dry-land areas, where inundations are irregular and white sand soils too poor to sustain a rich vegetation. High plant endemism and low diversity mark its varied physiognomies. Trees are low, curved and thin. Leaves are thick and resistant to desiccation. Epiphytes are abundant and diversified (orchids, bromeliads, and lichens).
Fauna is adapted to periodical flooding and water cycles. Terrestrial fauna migrates horizontally and/or vertically when waters rise. Aquatic fauna adapted its life cycle and reproduction to the periodic flooding and fructification of the trees. It is partially responsible for their dissemination. Fish diversity is high and its overall abundance is low. Rare river dolphins (Inia geoffroyensis, Sotalia fluviatilis) and manatees (Trichechus inunguis) are observed. More study is needed on insects, reptiles, birds, mammals and dry-land fauna.
Most of the local population of the area has been displaced and financially compensated by the Federal government. Only five families have yet to be installed in more favourable areas (1993). They live from survival small-scale agriculture and fishing.
People from the close-by community of Cauixi (1 family) and cities of Novo Airao and Manaus carry on with traditional and commercial fishing, small scale wood-cutting and hunting. Some building material companies from Manaus extract sands and stones along the river near the Ecological Station.
The Rio Negro is an important Amazonian ship transit channel. Every ship cruising the river has to pass along the Ecological Station’s limits, increasing the risk of pollution and facilitating eventual illegal activities. The area is being monitored to minimize these risks.
Another regional activity is tourism. The landscapes of Anavilhanas attract river excursions from Manaus with little detrimental impact and good income. Novo Airao, situated within the 10 km buffer zone, having 80 percent of its area covered by natural and indigenous reserves, may depend on tourism for enhancing the basic sustainability of its population.
There are two main bases in the Reserve: a floating base and one on the mainland. Both have accommodation, laboratory and lecture space for visiting scientists. It is a paradise for biologists and ecologists.
The Anavilhanas ESEC is surrounded by state-protected areas (The North and South Rio Negro Environmental Protected Areas and a State Park), which create a buffer zone that aids in its protection. In addition, there are approximately 50 communities in the surrounding area.
Access to the Ecological Station is by river, usually involving a 3-hour regional boat ride to reach its southern entrance, or a 4-hour drive (including the ferry ride) to the town of Novo Airao, its north-western entrance (170 km / 106 miles from Manaus).
The period from November to April marks high water on the River Negro, and half the islands are submerged, forcing the animals to take refuge on higher ground. When the waters retreat, the islands expose to view beaches and 90 km / 56 miles of canals, which intersect the whole region. Anavilhanas is near the Jau National Park, the largest forest reserve in South America at 2.27 million hectares, also on the Negro River.
The Anavilhanas Ecological Station was founded in 1981 by the federal government in order to protect the archipelago and in 1999 the Management Plan was elaborated by the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA).