The Sundarbans within Bangladesh and India is the largest single chunk of deltaic mangrove forest on this planet, formed at the mouth of the mighty Ganga- Brahmaputra river system. This Sundarbans is also the only mangrove habitat tiger-land on the globe, where the world famous 'Royal Bengal Tiger' (Panthera tigris tigris) is found their beautiful abode. The mangrove ecosystem in Indian Sundarbans covers an area of 4,266.6 km' (Naskar & Guha Bakshi, 1987). Out of this total, about 1,952.88 km' is covered by dense mangrove forests and 226.18 km' is as sparse mangrove cover area, spreading a total of 2,179.06 km' and the remaining 2088 km' is the estuarine rivers, tidal creeks and canals, which is estimated by the Department of Environment, Government of West Bengal along with Space Application Center, Ahmedabad, India in the year 1996. Naskar & Mandal (1999) emphasized the total land area of the Indian Sundarbans mangrove forest is about 2,300 km', consisting of about 56 major and several minor islands and the total water spread area is about 1,750 km'. The denuded sea shore and sand char-land/ mud flat area of the Sundarbans is also calculated about 216.6 km'. Total length of the coast line in Indian Sundarbans is about 120 km and it is spread over about 60 km - 90 km inside the main land, towards south to north.
Sundarbans mangrove forest area in Bangladesh is estimated to be about 66%, while only 34% of the total area falls under the political jurisdiction within Indian Sundarbans (Naskar & Mandal, 1999). Indian Sundarbans is situated within the longitude 88.10' E - 89.51' E and latitude 21.31' N - 22.30' N, under the jurisdiction of both 24 Parganas Districts (South and North) of West Bengal. This sea-land interphase mangrove ecosystem of Sundarbans comprises of about 55% forest land area and 45% water spread area, in the forms of tidal rivers, creeks, canals and vast estuarine mouths of the river Hugli, Baratala, Saptamukhi, Thakuran, Matla, Goasaba and Harinbhanga (Herobhanga), as encountered from west to east (Naskar & Guha Bakshi, 1987). These rivers along with numerous tidal creeks and canals render this entire mangrove ecosystem a criss-cross network like look. All these rivers are connected with the Bay of Bengal in their southern extremities. The tidal estuarine mouths are sometimes about 12 km broad, which carry the tidal sea-water and flood the mangrove forests at regular intervals. In the extreme west of this mangrove forest, the river Hugli (Ganga) meets the Bay, carrying fresh water from the upstream. Most of these other estuarine rivers mentioned above have lost their earlier connection with the river Ganga and as such, their tidal water have become more saline.