Detection of changes in mangroves along the Coreaú River Estuary, Northeastern Brazil from object-oriented classification in orbital images

Abstract

In South America, Brazil is the country with the largest extension of mangroves, covering approximately 7000 km, departing from the Oiapoque River, on the border between Amapá and French Guiana, to Praia do Sonho, in Santa Catarina. With population growth, there was an expansion of cities towards the coast and with them the development of agriculture and aquaculture. With the advent of remote sensors, the changes detected over the years in the extensive area of ​mangroves in Brazil and in the world, have been studied and quantified. In this context, the objective of this work was to evaluate the transformations occurred in the mangrove in a semiarid climate estuary and to quantify the losses and gains of areas, influenced by both natural and anthropic action. The mangrove of the Coreaú River estuary has undergone small and significant transformations over the past 28 years (1985-2013). There was an increase of 3% (7.17 km²) in 2013 compared to 1985, these transformations consisted of a 55% gain in mangrove area, due to the addition of muddy sediment, development of mangrove forest and regeneration of mangrove forests after the deactivation of the shrimp farms, and 45% loss, corresponding 38% to the natural loss of muddy material, due to the growth of apicum area, influence of wind, rain, flow and tides, and loss of 7%, related to anthropic action, represented by the shrimp farm and salt pans, built along the estuary. From the processing of optical images it was possible to identify the share of influence of these transformations (natural and artificial) near the mangrove and in which intervals of years there were the biggest or smallest changes.