Abstract

The present work integrates geomorphological, sedimentological, and palynological data with radiocarbon dating, as well as δ13C, δ15N, and C/N from sedimentary organic matter previously published in order to provide models of mangrove dynamics from northern and southern Brazil. The mangrove dynamics have been analyzed within the context of millennial, secular, and decadal climatic and sea-level changes. According to these models, climatic changes and sea-level fluctuations caused by regional or global climatic change have affected significantly the Brazilian mangrove area during the Holocene. However, the impacts on mangroves, caused by those driving forces, depend on the environmental factors of each littoral such as topography, wave and current energy, coastal morphology, and mainly the input of nutrients, sediment, and freshwater. Consistent with multi-proxy analyses and the projected sea-level rise and climatic changes, mangroves will continue to migrate landward to occupy higher parts of the tidal flats. However, due to the significant topographic difference between tidal flats and coastal plain, this process may cause a decrease in mangrove area along the northern littoral. Considering the decrease in rainfall, it will cause a reduction in fluvial discharge, and consequently, the tidal water salinity will increase upriver. This dynamic of the estuarine salinity gradients will cause a replacement of várzea vegetation (freshwater wetland) by mangroves (brackish water wetland) along the fluvial flood flats. Regarding the southeastern Brazilian littoral, erosion of beach ridges, and expansion of lagoons, estuaries, and mangroves are expected according to sea-level rise and decrease of rainfall. The assessment of mangrove dynamics according to climatic and sea-level changes in a millennial, secular, and decadal time scale have been crucial for the understanding of their survival ability under future scenarios with probable accelerated SLR rates as well as intensification of extreme climatic events for this century.