The world’s largest mangrove ecosystem Sundarbans lies in the southwestern part of the Ganges-Brahmaputra Delta. The health, function, and ecosystem services of the mangrove forest depend on the availability of freshwater flow within the deltaic system. The rivers, which used to feed the delta and nourish the mangrove ecosystem now stand disconnected from their upstream freshwater sources. The unavailability of freshwater restricts the growth of freshwater-loving mangroves and has the potential to affect the health of the existing mangroves limiting their ability to provide ecosystem services. Due to the high salinity, the natural reproduction of these valuable freshwater-loving floral species gradually got ceased. High salinity is considered a stress factor influencing the health, growth, productivity, and distribution of mangrove plants. In this circumstance, the main objective of the study is to monitor the spatiotemporal change of the mangrove ecosystem of Sundarbans in terms of species assemblage, floral diversity, biomass, canopy cover, forest health, etc. Remote sensing techniques and field measurements were used to perform an in-depth mangrove genus-level classification (Maximum Likelihood Classifier). To assess the plant species diversity, Shannon-Wiener Index was used in different plots of the Sundarbans to get an idea of the rich biodiversity of these coastal ecosystems. Different vegetation indices such as NDVI, OSAVI, SAVI, TDVI, etc. were estimated to assess the health of the mangrove forest. The biomass and carbon sequestration potential of the mangrove forest was assessed using field data and microwave remote sensing techniques. The result shows the declining trend of freshwater-loving mangroves from the central section of Sundarbans and an increasing trend of saline water-loving mangroves by replacing the others.