Análise espaço-temporal da vegetação do manguezal no rio Ceará, Ceará, Brasil

Abstract

Mangrove ecosystem occurs in Brazil in estuaries, shore lagoons and marine channels inside land, from the extreme North of the country, to well beyond the Tropic of Capricorn, near Laguna, Brazilians’ south coast. In the Ceará state (02°46 S), Brazil´s northeast region, the climate is semi-arid, with seasonal rains and high reception of solar radiation. In the last few decades the human occupations intensify in Ceara river estuarine complex, and modify the landscape in results of their actions, interfering in the natural development of the mangrove ecosystem. This case study reports a description and an analyses of the temporal-spatial development of the mangrove area in the Ceará river (Fortaleza – CE), focusing on new colonization areas in abandoned saltworks. It was produced thematic maps estimating the mangrove areas and the saltwork areas in the years of: 1968, 1997, and 2009 using remote sensing techniques. In 2009 the mangrove area was 1006.6 ha, 65% more than in 1968, the growth rate was 133.25 ha/10years between 1997 and 2009. In abandoned saltworks areas it was evidenced 395 ha of new colonized mangroves areas. A fitosociologic study was accomplished to demonstrate the detailed description of the mangrove forest structure. The mangrove forest near the main channel of the Ceará river is described as fringe, an advance development forest, with dominance of Rhizophora mangle and Avicennia spp., medium height of 10 meters, medium DHB 14,06 cm and density of 1333.33 trunk/ha. Down to the terrestrial environment it´s evidenced basin mangrove forests, in new mangrove´s colonization areas. The pioneer specie was Laguncularia racemosa associated with other associated species Portulaca oleracea (beldroega) and Batis marítima (brejo do mangue). Although the quantitative increment in mangrove forest areas the environment quality was considered low, due the evidenced of the variety of environmental impacts. To highlight the environment services it was necessary a systemic analysis approach of the flows of energy and matter. The relation between the human activities and the environment fluxes related shows the interference of the environment impacts in the environment services, for example, the shore fluxes (sediment deficit) fluvial-marine flux (estuary salinization and water contamination) and the gravitational fluxes (abandoned saltwork, soil impermeabilization and dense urban occupation in dune areas). Consideration about the state resolution COEMA n° 02/2002 were made to discuss the recent flexibilization of Brazilian environmental legislation, in order to provide legal tools to appropriations of mangrove areas to industry exploration, the case of shrimp farms legalization. A new posture in mangrove conservation programs in the Ceará river would represent higher costs of opportunities in a sustainability receipt of human development in estuary regions and shore areas in the Ceará state, in Brazil and in the whole world. The Ceará river recuperation will only be possible after the mitigation of the main environmental impacts. It is recommended to install priority conservation zones, natural regeneration monitoring zones and environment rehabilitation zones, in order to enhance the mangrove management plan.