species of fish, 315 species of birds and 53 species of reptiles; besides numerous species of phytoplankton, fungi, bacteria, zooplankton, benthic invertebrates, molluscs, reptiles, amphibia and mammals. Species composition and community structure varies east to west, and along the hydrological and salinity gradients. Ecologically, the forest is particularly important as a barrier to cyclones, tidal upsurges, etc. It is also acting as a huge sink of unlimited capacity for absorbing CO2 and other pollutants from air and water which makes the surrounding environment free from pollution.
The mangroves of the Sundarban are unique when compared to non-deltaic coastal mangrove forest. Unlike the latter, the Rhizophoraceae are of only minor importance and the prime species are sundri Heritiera fames, from which the Sundarban takes its name, and gewa Excoecaria agallocha. The reason for this difference is the large freshwater influence in the north-eastern part and the elevated level of the ground surface. The Sundarban can be classified as moist tropical seral forest, comprising a mosaic of beach forest and tidal forest. Of the latter, there are four types: low mangrove forests, tree mangrove forests, salt-water Heritiera forests and freshwater Heritiera forests. Sundarban West occurs within the salt-water zone, which supports sparse Ecoecaria agallocha, a dense understory of Ceriops, and dense patches of hantal palm Phoenixpaludosa on drier soils. Dhundal and passur Xylocalpus spp., and Bruguiera occur sporadically throughout the area. Sundri and gewa cover most of the Sundarban but Oryza coarctata, Nypa fruticans and Imperata cylindrica are prevalent on mud flats. Large stands of keora Sonneratia apetala are found on newly accreted mudbanks and provide important wildlife habitat.
The Sundarban is the only remaining habitat in the lower Bengal Basin for a variety of fauna1 species. The presence of 49 mammal species has been documented. Of these, no less than five spectacular species, namely
Page 3 of 8
Javan rhinoceros Rhinoceros sondaicus (CR), water buffalo Bubalus bubalis (EN), swamp deer Cervus duvauceli (VU), gaur Bosfrontalis (VU) and probably hog deer Axis porcinus (LR) have become locally extirpated since the beginning of this century. The Sundarbans of Bangladesh and India support one of the largest populations of tiger Panthera tigris (EN), with an estimated approximately 700 (2004). These tigers are well-known for the substantial number of people they kill; estimates range from twenty and eighty people per year. They are the only man-eating tigers left in the world, though they are not the only tigers who live in close proximity to humans.
The varied and colorful bird-life to be seen along its waterways is one of the Sundarbans’ greatest attractions. A total 315 species have been recorded, including about 95 species of waterfowl and 38 species of raptors. Among the many which may be readily seen by the visitor are no less than nine species of kingfisher, including brown-winged and stork-billed kingfishers, Pelargopsis amauropterus (NT) and P. capensis, respectively; the magnificent white-bellied sea-eagle Haliaeetus Zeucogaster which, at a density of one individual per 53. l km of waterways, is quite common; also the much rarer grey-headed fish eagle Zchthyophaga ichthyaetus (NT), Pallas’s fish-eagle Haliaeetus Zeucoryphus and several other raptors. Herons, egrets, storks, sandpipers, whimbrel, curlew and numerous other waders are to be seen along the muddy banks and on the chars or sandbanks which become exposed during the dry season. There are many species of gulls and terns, especially along the coast and the larger waterways. Apart from those species particularly associated with the sea and wetlands, there is also a considerable variety of forest birds such as woodpeckers, barbets, shrikes, drongos, mynahs, minivets, babblers and many others.
Some 53 reptile species and eight of amphibians have been recorded and of these, mugger Crocodyluspalustris (VU) is now extinct, probably as a result of past over-exploitation, although it still occurs in at least one location nearby. Estuarine crocodile C. porosus still survives but its numbers have been greatly depleted through hunting and trapping for skins.
Four species of marine turtle have been recorded from the area, olive ridley Lepidochelys olivacea (EN) being the most abundant. Green turtle Chelonia mydas (EN) is rare due to excessive fishing, while loggerhead Caretta caretta (EN) and hawksbill Eretmochelys imbricata (CR) are not common although there have been some reported on the beaches (Hussain and Acharya, 1994). River terrapin Batagur baska (EN) is also present. The eighteen recorded snake species include king cobra Ophiophagus hannah and spectacled cobra Naja naja, three vipers and six sea-snakes(S alter, 1984). Over 120 species of fish are reported to be commonly caught by commercial fishermen in the Sundarban. Freshwater species are alarmingly decreased day by day. Crustacea account for by far the largest proportion of animal biomass, with an estimated 40 million kilograms of fiddler crabs and 100 million kilograms of mud crabs (Hendrichs, 1975). The nutrient-rich waters of the Sundarban also yield a considerable harvest of shrimps, prawns and lobsters. The area supports a varied insect population including large numbers of ants, honey-bees etc. and honey and beeswax are economically very important products. The insect life of the Sundarban has been little studied.