Manguezal

The Brazilian coast has, in a surface of around 20 thousand km2, from the Orange Cape, in Amapá, to the municipality of Laguna, in Santa Catarina, a narrow strip of forest called "Manguezal" or "mangue" (mangrove swamp). This is composed by a small number of tree species and develops mainly in the estuaries and river mouths, where there is salt water and places semi-protected from the action of the waves, but open to receive sea waters. This is an environment with a good supply of nutrients, where under the muddy soils there is a texture of roots and vegetable matter partially decomposed, called peat. In the estuaries, the muddy beds are crossed by tide channels ("gamboas") used by the fauna for their movements between the sea, rivers and the "Manguezal".

Brazil has one of the largest extensions of "manguezal" in the world. Underrated in the past because the presence of the "mangue" was intimately associated to yellow fever and malaria - illnesses already under control - the word "mangue" has, unfortunately acquired a meaning of disorder, dirtiness or suspicious place. The "Manguezal" has been considered, for a long time, an inhospitable environment, due to the constant presence of different species of mosquitoes such as "borrachudos", "pólvora" and "mutucas". The dark, muddy, unattractive forests, infested with irritant insects, has caused people to think, until the mid 70's, that the progress of the marine coast was equivalent to clean beaches, landfills with sanitation, ports confined by concrete, and cultivation experiments to use the lands of the old "manguezais". Despite the great economic and social importance of the "Manguezal" this approach was in part responsible for the construction of ports, bathing resorts and coastal roads in its areas, reducing the extension of the "mangues".

Contrary to other forests, the "manguezais" are not rich in species, but stand out for the great abundance of the populations living in them. For that reason they may be considered one of the most productive natural environments in Brazil.

Only three trees constitute the "mangue" forests: the red or "bravo" mangrove, the white mangrove and the "seriba" or "seriuba" mangrove. They live in the tidal zone and have a series of adaptations: buttress roots (which supply with oxygen the other buried roots and reduce the impact of the waves from the tides), capacity for ultra-filtration of the salt waters and development of plantules in the maternal plant, to be later dispersed by sea water. A few species can be added to the flora of "Manguezal" such as the fern of the "mangue", the Spartina grass, the bromeliad Tillandsia usneoides, the lichen Usnea barbata (the last species are known as old man's beard, and very similar to each other) and the hibiscus.

In the North of the country, the thick "mangue" forests have trees which might reach 20 meters of height. In the Northeast region, there is a kind of "Manguezal" known as "dry mangue", with small sized trees in a sub-stratum of high salinity. In the Southeast of Brazil, the "mangue" has the aspect of a shrub forest.

The "mangue's" dark ground is covered by water in the high tide. Rich algae communities grow over the buttress roots of trees, in the area covered by the tide, including red, green and blue algae. The trunks permanently exposed and the tree tops are poor in epiphytal plants. Bacteria and fungi decompose the "Manguezal" leaves and the food chain is based on the use of the dregs resulting from this decomposition.

The fauna includes various species of crabs, forming enormous populations in the muddy beds. The oysters, mussels and barnacles feed themselves by filtering from water the small fragments of vegetable dregs, rich in bacteria. There are also species of mollusks that perforate the wood of tree trunks, building in them their calciferous tubes and feeding on micro-organisms which decompose the trunks' lignin, helping the natural renovation of the ecosystem through the fall of old trees, heavily perforated.

Prawns also enter the "mangues", during the high tide, to feed. Many fish species of the Brazilian coast depend on the food sources of the "Manguezal", at least in their young phase. They include "bagre" (catfish), robalo, "manjuba" (sea fish of the family Engraulidae) and mullet. The richness of fish attract predators such as some species of shark and dolphins. The yellow chin alligator and the frog Bufo marinus might occasionally be found there.

Typical birds are few, due to the small diversity of flora; however, some species use the "mangue" trees as points of observation, rest and nesting. These birds feed on fish, crustaceans and mollusks, especially at low tide, when the muddy beds are exposed. Among the mammals, the "coati" (a tropical raccoonlike mammal) is specialist in feeding on crabs. The otter, an agile fisherman, is frequent, as is the "guaxinim" (crab eating raccoon).

The "manguezais", used by the "sambaqui" men (tribes which inhabited the Brazilian coast during the pre-historic period) more than 7 thousand years ago, and since then by the populations who succeeded them, provide protein rich food for the Brazilian coastal population. The fishing of prawns, crabs, molluscs and fish is a survival source for the inhabitants of the coast.

Although protected by law, the "Manguezal" still suffers with gratuitous destruction, domestic and chemical pollution of waters, petrol spillages and badly planned landfills.

by Francis Dov Por