Location and General Description
This tropical ecoregion holds the mangrove patches around the mouth of the Amazon, Baía de Marajó extending north to Cabo Caciporé including the Parque National de Cabo Orange. Its terrain is composed of fine grained clay and sediment deposited by the Amazon River, which form hundreds of islands and mudflats that are continuously colonized and stabilized by the salt tolerant mangrove species. High tidal ranges of 5-7 meters, combined with flat topography, allow the mangroves to extend up to 45 km inland from the coast. The climate is humid tropical, with temperatures ranging between 24° C and 32° C. Exceptional development of the mangroves is also made possible by high freshwater inputs from rainfall that averages 2,500 mm a year but may be as high as 4,000 mm a year, and from the Amazon River system. Although well developed, the distribution of mangroves in this ecoregion is somewhat restricted by the presence of freshwater species, that include typical Amazon freshwater hardwoods. (Kjerfve and Lacerda 1993; Ubiratan et al. 1999).
Rhizopora mangle is the most frequently occurring mangrove species and is found closest to the coast at heights of up to 25 m. Also particularly well developed along the north coast of Brazil is Avicennia germinans and A. schaueriana, which may be over 1 meter in diameter and reach heights of up to 45 meters. R. racemosa R. harrisonii, Laguncularia racemosa and Conocarpus erectus are found in the transition zone, leading to dry forest areas. Non-tree species associated with these mangroves are Spartina alterniflora that grows on the seaward fringe, and Hibiscus tiliaceus and the fern Acrostichum aureum, that are both found in the landward margins and dry saline areas within the mangroves. Species found associated with these mangroves because of their location adjacent to tropical forests and because of high freshwater input include the tropical forest species, leguminosae vine (Dalbergia brownei), and Apocynaceae liana (Rhabdadenia biflora); freshwater macrophytes, Araceae Montrichardia arborescens, and Leguminosae Mora oleifera; and palm species, Euterpe oleracea and Orbygnia martiana (Kjerfve and Lacerda 1993).
Rare and endangered species found in this ecoregion include the birds, scarlet ibis (Eudocimus ruber), and wattled jacana (Jacana jacana), the mammals tucuxi (Sotalia fluviatilis) and manatee (Trichechus manatus), and two marine turtles, the green turtle (Chelonia mydas) and the leatherback (Dermochelys coriacea).
This ecoregion contains approximately 28% of the total Brazilian mangrove area, much of which is intact because of low population density and inaccessibility (Kjerfve and Lacerda 1993). However, the region also includes the urban area of Belém, where much of the region’s population is concentrated. There are 5 environmental protection areas in this coastal zone but it is not clear what percentage of these consist of mangroves.
Types and Severity of Threats
The main economic activities associated with environmental risks and concerns are of the ecoregion are subsistence agriculture, extensive grazing of livestock, tourism, timber extraction, mineral exploration, commercial and industrial development, land speculation in conservation areas, development of transportation infrastructure that involves the filling of mangrove areas, and urban expansion into mangrove areas. These mangroves are also important to the subsistence economy of numerous artisanal fishermen, particularly for their abundance of crabs. In addition to fishing, mangroves are used as timber for construction of boats and houses, and their barks as a source of tannin used to dye ship sails. They are also used for firewood and charcoal (Kjerfve and Lacerda 1993; Ubiratan et al 1999).
Justification of Ecoregion Delineation
Classification and linework for all mangrove ecoregions in Latin America and the Caribbean follow the results of a mangrove ecoregion workshop (1994) and subsequent report (Olson et al. 1996).
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Prepared by: Sylvia S. Tognetti and Christine Burdette
Reviewed by: In process