Áreas alteradas em manguezais: planície costeira bragantina, Pará

Abstract

The Bragantine coastal plain, located in northeastern Pará, has about 40 km of coastline and is embedded in a tidal zone dominated by macromarges. Mangroves are the dominant ecosystem: they occupy about 95% of the tidal plain and constitute a true large coastal forest, interspersed with salt marshes and sandy strands. The alterations in the mangroves of the Coastal Plain are significant, occurring along some transects, of which one of the most representative is the one between the city of Bragança and Ajuruteua beach, along 36 km of highway, where natural and anthropic modifications are observed. This was the main reason that made us choose this area as the location and theme of our work. The methodology consisted of literature review, preparation of reading sheets, presentation of a seminar in the CCTE, participation in other courses and seminars (FCAP, UFPA.), field and office work, and analysis of georeferenced spatial maps. Three main woody species in different states of development were identified, namely: Rhizophora mangle L. (Rhizophoraceae), Laguncularia racemosa (L.) C.F. Gaertn. (Combretaceae ) and Avicennia schaueriana Stapf& Leechm. ex Moldenke (Verbenaceae), as well as associated vegetation. The occurrence of the species as well as the structure of the forests vary according to the stresses acting on the ecosystem. Among others, the construction of the Bragança-Ajuruteua road caused localized changes in the feeding of the mangrove by tidal waters, its decline and death on one side of the road. Another impact is represented by the advance of urbanization, with lack of basic sanitation and pollution of stretches of the beach, as well as the subdivision of mangrove areas near the beach. One of the most representative natural impacts is observed at Ajuruteua beach, where coastal erosion causes the retreat of the coastline and disturbs the mangrove ecosystem at the upper limit of the strand and at the mouth of some water courses. Considering the ecological functions of mangroves and their role in protecting the genetic heritage, it is urgent to preserve habitats like this one, which, despite being officially protected by the Forest Code since 1965 and being permanent preservation areas (law 4771, and resolutions of CONAMA, IBAMA, CIRM...), are being constantly degraded.