Wetlands are considered the most biologically diverse of all ecosystems and play an important role in maintaining of biodiversity. The wetlands of Bangladesh serve a diverse habitat of various flora and fauna. The majority of country's land was formed by river alluvium from Ganges and the Brahmaputra and their tributaries and possesses a large number of wetland areas which are mainly rivers and streams, freshwater lakes and marshes, flooded cultivated fields, estuaries and mangrove swamp.