Mangrove Response to Land Use Change in Estuaries along the Semiarid Coast of Ceará, Brazil

Abstract

Mangroves cover an estimated area of approximately 12 to 20 million ha worldwide and serve as protection for the coastline from erosion and flooding. Nearly 70 mangrove species are considered endangered and could disappear in the next decade, which would have devastating economic and environmental consequences for coastal communities because of their ecological and economic importance. The annual rate of disappearance of coastal ecosystems is four times greater than the rate of the disappearance of rain forests. Mangroves suffer great pressure from the rapid conversion of forests into agricultural and urban areas, and, in these scenarios, climate change promotes specific pressures on mangroves and may increase the effects of anthropogenic activities. The focus of this study was to map the changes in mangrove areas in six river estuaries in Ceará, northeastern Brazil, between the years 1992 and 2011 and identify the main drivers of these changes. The results showed an increase in mangrove areas of five estuaries, while one estuary showed a decrease in mangrove area. Changes in river output capacity and sediment accumulation in the estuaries were associated with dam construction in the watersheds and can be responsible for new upstream mangrove areas in newly formed islands and along river banks. Abandoned saltpans also contributed to expansion of the mangrove areas. Deforestation for the construction of shrimp farms was the main cause of decreases in mangrove area, especially in the Pirangi estuary.