Anavilhanas Ecological Station

Description

Area: 350.018 hectares - Perimeter: 380 Km
Climate: hot and humid tropical, with one to two month dry season.
temp: 27,1 ° year average
pluv: 2.075 mm total /year
Altitude: 5 - 600 m.

Geomorpholoqy: The Ecological station is constituted by a 100.000 ha. archipelago, of hundreds of elongated islands and canals within the Rio Negro riverbed, covered by inundated forests. Included to these are 250.000 ha. of not-flooded forests on the riversides. The river is 1 to 3 Km wide and 5 to 35 m deep. Sessonal variation of the water is +/- 10 m. Water pH varies between 3,7 and 5,5.

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 (stilt 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 m deep, are temporarily isolated during the dry season. Some channels are permanently open and have faster stream. Islands and channels location is changing overtime, due to the seasonal water cycles, periodic floods, acidity and debit fluctuations.

Not-flooded area's of the margin separate minor affluent of the Rio Negro. They are tabular formations of yellow laterite soils and smooth altitude variation.

Vegetation

Periodicaliv-flooded forests: islands and river margins are mostly covered by a low, dense, periodically-flooded rainforest (Igapo forests). Its vegetation shows specific adaptation to months duration floods, like aerial root system, specialised reproduction cycle and fast grow. Palm-trees are locally abundant.

Not-flooded forests are higher, more complex, with dense canopy, isolated elevated trees and dense sub-wood vegetation. There are two types: lowland and sub-mountain. Lowland forests occurs between 5 and 100 m altitude and sub-mountain, higher up to 600 m.

Forested shrub-lands (Campinarana arborea) are specialised ecosystems occurring on some islands of the archipelago and on dry-land area's, where inundation's 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, bromelieds, lichens).

Fauna

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.

Local Ponulation and thrests on the area.

Most of the local population of the area has been displaced and financially compensated by the Federal govemment. Five families only remain to be installed in more favourable area's (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 (+I-15.000 inhab.) and Manaus (more than 1 million) do traditional and commercial fishing, small scale wood-cutting and hunting. Some building material companies from Manaus extract sands and stones along the river neor the Station. Legal protection and surveillance is reducing threats on the area.

The Rio Negro is an important Amazonian ship transit channel. Every ship cruising the river has necessarily to pass along the Ecological Station limits, putting it at risk of pollution and facilitating eventual illegal activities. The area is being monitored to minimise these risks.

Other regional activity is tourism. The landscapes of Anavilbanas attract river excursions from Manaus with little impact and good income. Novo Airao, situated within the 10-Km buffer zone, having 80% of its area covered by natural and indigenous reserves, may depends on tourism for enhancing the basic sustain of its population.

Access and infrastructure

Main access is by boat, on the Rio Negro, from the City of Manaus. The Station has three floating posts located in the centre of the archipelago, and one guard post on firm-land. There is no tourism infrastructure.