Sundar Ban Forest The word “Sundarban” most probably comes from the Bangla words for “beautiful forest”. A large part of the forest is made up of Sundari trees. The Sundarban mangroves surround the Ganges delta and are the largest mangrove area in the world. One third of the area belongs to India, two thirds to Bangladesh – the mangrove trees don’t care much about borders, and neither do the animals living there. Everywhere you can see their roots coming up through the soil; as the soil is very muddy, almost no oxygen comes through and this is the way the trees can still breath. The walking does not get any easier, though. Sundari tree grows in saline waters and has very hard wood, two qualities that make it excellent boat material and liable to illegal cutting. The animals are also at risk because of our human interests. Poverty makes it almost impossible to implement the environmental laws. If you have nothing to eat, it is hard to lie awake over the continued existence of a mangrove forest, however beautiful it may be. Sundarbans, The largest single block of tidal halophytic mangrove forest in the world, located in the southern part of Bangladesh. It lies on the Ganges-Brahmaputra Delta at the point where it merges with the bay of bengal. The forest lies a little south to the Tropic of Cancer between the latitudes 21º30´N and 22º30´N, and longitudes 89º00´E and 89º55´E. With its array of trees and wildlife the forest is a showpiece of natural history. It is also a centre of economic activities, such as extraction of timber, fishing and collection of honey. The forest consists of about 200 islands, separated by about 400 interconnected tidal rivers, creeks and canals. Sundarbans was originally measured (about 200 years ago) to be of about 16,700 sq km. Now it has dwindled to about 1/3 of the original size. Because of the partition of India, Bangladesh received about 2/3 of the forest; the rest is on the Indian side. It is now estimated to be about 4,110 sq km, of which about 1,700 sq km is occupied by waterbodies. The forest lies under two forest divisions, and four administrative ranges viz Chandpai, Sarankhola, Khulna and Burigoalini and has 16 forest stations. It is further divided into 55 compartments and 9 blocks. The Sundarbans was declared as a Reserve Forest in 1875. About 32,400 hectares of the Sundarbans have been declared as three wildlife sanctuaries, and came under the UNESCO World Heritage Site in 1999. These wildlife sanctuaries were established in 1977 under the Bangladesh Wildlife (Preservation) (Amendment) Act, 1974. These are Sundarbans West (9,069 ha), Sundarbans South (17,878 ha), and Sundarbans East (5,439 ha). Geology :- The tract of the Sundarbans is of recent origin, raised by the deposition of sediments formed due to soil erosion in the Himalayas. The process has been accelerated by tides from the sea face. The substratum consists mainly of Quaternary Era sediments, sand and silt mixed with marine salt deposits and clay. Geologists have detected a southeastern slope and tilting of the Bengal basin during the Tertiary. Because of neo-tectonic movements during the 10th-12th century AD, the Bengal Basin titled eastward. Evidence from borehole studies indicate that while the western side of the Sundarbans is relatively stable, the southeastern corner is an active sedimentary area and is subsiding. Soil:- Soils of the Sundarbans mangrove forest differ from other inland soils in that they are subjected to the effects of salinity and waterlogging, which naturally affect the vegetation. In places soils are semi-solid and poorly consolidated. The pH ranges widely from 5.3 to 8.0. Although the Sundarbans soil is in general medium textured, sandy loam, silt loam or clay loam, the grain size distribution is highly variable. Silt loam is dominant textural class. Sodium and calcium contents of the soil vary from 5.7 to 29.8 meq/100g dry soil and are generally low in the eastern region and higher towards the west. The available potassium content of the soil is low, 0.3-1.3 meq/100g dry soil. Organic matter content varies between 4% and 10% in dry soil. Soil salinity increases from east (slight to moderate) to west (highly saline), but the salinity is not uniform from north to south throughout the forest. Climate Since the forest is located on the south of the Tropic of Cancer and bounded by the northern limits of the Bay of Bengal, it is classified as tropical moist forest. The temperatures in the Sundarbans are fairly equable than those of the adjacent land areas. The average annual maximum and minimum temperatures vary between 30º and 21ºC. High temperatures occur from mid-March to mid-June and low in December and January. The mean maximum temperature for the hottest months has been recorded as 32.4ºC at Patuakhali, in the east of the Sundarbans. The mean annual relative humidity varies from 70% at Satkhira to 80% at Patuakhali. Humidity is highest in June-October and lowest in February. Annual rainfall in the Sundarbans is in the range of 1640-2000 mm, rainfall increases from west to the east. Most rainfall occurs during the monsoon from May to October. Frequent and heavy showers occur from mid-June to mid-September. Often storm accompanied by tidal waves result widespread inundation and cause damage to vegetation and animal life. Vegetation The vegetation is largely of mangrove type and encompasses a variety of plants including trees, shrubs, grasses, epiphytes, and lianas. Being mostly evergreen, they possess more or less similar physiological and structural adaptations. Most trees have pneumatophores for aerial respiration. The prominent species is Sundari (Heritiera fomes) and Gewa (Excoecaria agallocha). Prain (1903) recorded 334 species under 245 genera. Of these 17 are pteridophytes, 87 monocotyledons and the rest are dicotyledons. The plant species include 35 legumes, 29 grasses, 19 sedges, and 18 euphorbias. Of the 50 true mangrove plant species recorded, the Sundarbans alone contain 35. Almost all mangrove plant species are evergreen, dwarf, shrubby or tall trees, and grow gregariously without leaving any space on the floor. In the Sundarbans the saltwater forest is situated in the south-western part where Gewa (E. agallocha), Goran (Ceriops decandra), Keora (Sonneratia apetala), Ora (S. caseolaris), Passur (Xylocarpus mekongensis), Dhundul (X. granatum), Bain (Avicennia alba, A. marina, A. officinales), and other rhizophores, and Hantal (Phoenix pelludosa) dominate. The typical mangrove species dominate the central part of the forest. The moderate saltwater forest covers most of the southern parts of Khulna and Bagerhat districts where Sundari is the dominant species. There is a thick mat of the nipa palm or \'Golpata\' (Nipa fruticans) by the side of almost all the canals. The moderately freshwater zone results from the large amount of water, which flows down the Passur, Haringhata and Burisher, maintaining the surface water at a lower level of salinity. The Sundarbans shows some distinct phyto-succession, where the newly formed lands are occupied by some pioneer species viz Leersia hexandra, wild rice (Potresia species), followed by Avicennia, Sonneratia and Aegiceras. The secondary succession occurs due to Ceriops, Excoecaria, Bruguiera, Heritiera, Xylocarpus and Rhizophora. Tiger fern (Achrostichum aureum) mostly covers the ground floor, which is common in saltwater and moderately saltwater zones. Tigers use these bushes to camouflage themselves. Fauna The Sundarbans hosts a large variety of animals. It is the last stronghold of the bengal tiger (Panthera tigris). Within the forest habitats there are about 50 species of mammals, about 320 species of inland and migratory birds, about 50 species of reptiles, 8 species of amphibians, and about 400 species of fish. Besides the spectacular Royal Bengal Tiger, the other notable mammalian fauna are Spotted deer (Cervus axis), Barking deer (Muntiacus muntjak), Rhesus macaque (Macaca mulatta), Jungle cat (Felis chaus), Leopard cat (Prionailurus bengalensis), the Indian porcupine (Hystrix indica), Otter (Lutra perspicillata), and wild boar (Sus scrofa). deer and wild boar constitute the main prey for the tiger. Some species including the Bengal tiger are endangered. The ecological diversity of the Sundarbans supports a large variety of birds. Among the total number of species recorded, most are resident. Over 50 species are known to be migratory and are mostly represented by the waterfowls. The egrets, storks, herons, bitterns, sandpipers, curlew, and numerous other waders are seen along the muddy banks. There are many species of gulls and terns, especially along the seacoast and the larger waterways. Accipitridae (kites, eagles, vulture, harrier etc) is represented by about 22 species. Nine species of kingfishers are available in the forest. The rich avifaunas of the forest include species of woodpeckers, barbets, owls, bee-eaters, bulbul, shrikes, drongos, starlings, mynas, babblers, thrush, oriole, flycatchers, and many others. Of about 50 species of reptiles the largest member in the Sundarbans is the Estuarine crocodile (Crocodylus porosus), some of which may attain a length of about seven metres. Although once they were abundant in this mangrove habitat, their total number is now estimated to be around 250. Species of lizards, including the Monitor Lizards Varanus, turtles, and snakes are well- represented. Among the snakes, the King Cobra (Ophiophagus hannah), Russell\'s Viper (Vipera russellii), Rock python (Python molurus), Banded Krait (Bungarus fasciatus) and several species of sea snakes are notable/ Only eight species of amphibians have been reported from the Sundarbans. The green frog (Euphlyctis hexadactylus) is mostly observed in Chandpai area of the mangrove forest. The other forest amphibians include the Skipper frog (E. cyanophlyctis), Cricket frog (Limnonectes limnocharis), Tree frog (Polypedates maculatus), and the common toad.