Temporal changes of mangrove vegetation boundaries in Amazonia: Application of GIS and remote sensing techniques

The present work analyses a 25-year time series of radar and satellite images, and identifies areas with losses and gains of vegetation coverage along similar to 166 kmof Para's coastline (North Brazil) and in the inner parts of the Braganca peninsula. The geomorphology of this region has significantly changed in recent years. A result of these changes has been a retreat of the mangrove vegetation along the coastline, mainly due to landward sand migration, which covers the mudflat and asphyxiates the vegetation. Image analysis suggests that the loss of vegetation coverage has been the dominating process in the last 25 years, occurring on similar to 42% of the Braganca coastline and adjacent areas. Vegetation has remained stable along similar to 39% of the coastline, while mud sedimentation has allowed mangrove development along similar to 19% of it. On the other hand, during this period of time, mangroves have invaded 3.4 km(2) (similar to 38%) of the elevated herbaceous flats in the highest sectors of the Braganca peninsula. Despite other possible causes for mangrove death along the coastline, such as littoral drift currents or cyclical changes in coastal sediment dynamics, the invasion of mangrove into herbaceous elevated flats in the central peninsula cannot be attributed to these factors. The current dynamics of vegetation coverage change seem to be compatible with a long-term trend related to the predicted rates of sea-level rise.