The name Sundarbans is thought to be derived from sundri or sundari (Heritiera fomes), the name of the large mangrove trees that are most plentiful in the area. The forestland transitions into a low-lying mangrove swamp approaching the coast, which itself consists of sand dunes and mud flats. Mangrove forests constitute about two-fifths of the Sundarbans region’s overall surface area, with water covering roughly half of that area. The landscape is constantly being transformed by the erosional forces of the sea and wind along the coast and by the enormous loads of silt and other sediments that are deposited along the myriad estuaries. Human activity has also altered the landscape, notably through forest removal, which accelerates erosion. In addition, because considerable amounts of river water have been diverted upstream for irrigation and other uses, salinity in the mangrove swamps has moved farther inland, especially in the Indian sector of the territory.