Sundarbans is the largest mangrove forest of the world. It is an evergreen forest which can withstand saline water of the sea. The Sundarban forest lies in the vast delta on the Bay of Bengal formed by the super confluence of the Ganges, Hooghly, Padma, Brahmaputra and Meghna rivers across southern Bangladesh. The seasonally flooded Sundarbans freshwater swamp forests lie inland from the mangrove forests on the coastal fringe. Most parts of Sundarbans is located in the south-west part of Bangladesh in Khulna division. The Sundarbans extends about 274 km (170 mi) along the Bay of Bengal and about 100 km (62 mi) inland. It contains a vast number of tidal rivers and innumerable islands, but very little development or agriculture.
Sundarbans is the habitat of diverse flora and fauna, including 109 indigenous species of mammals, 295 types of birds, 119 kinds of reptiles, 19 different amphibians, 200 varieties of marine and freshwater fish and countless varieties of plants. The rhesus monkey is common, and gibbons and lemurs are also found. Countless birds and insects also live in the forest. The Sundarbans area is one of the principal remaining domains of the endangered Royal Bengal Tiger, which is one of the most exotic and rarest animals on earth. Although the tiger is officially protected, illegal poaching is known to occur. Besides tigers various animals such as spotted deer, black bear, crocodile, monkey, leopard, fresh water dolphins and so on resides in Sundarbans. Other animals living in Sundarbans include mongoose, jackal, Bengal fox, wild boar, parakeet, kingfisher, vulture, and swamp crocodile.
The dominant mangrove species of Sundarbans is Heritiera fomes, which is locally known as sundri or sundari. Mangrove forests are not home to a great variety of plants. They have a thick canopy, and the undergrowth is mostly seedlings of the mangrove trees. Besides the sundari, other tree species in the forest include Avicennia, Xylocarpus mekongensis, Xylocarpus granatum, Sonneratia apetala, Bruguiera gymnorhiza, Ceriops decandra, Aegiceras corniculatum, Rhizophora mucronata, and Nypa fruticans palms. Twenty-six of the fifty broad mangrove species found in the world grow well in the Sundarbans. The commonly identifiable vegetation types in the dense Sundarbans mangrove forests are salt water mixed forest, mangrove scrub, brackish water mixed forest, littoral forest, wet forest and wet alluvial grass forests. The Bangladesh mangrove vegetation of the Sundarbans differs greatly from other non-deltaic coastal mangrove forests and upland forests associations. Unlike the former, the Rhizophoraceae are of minor importance.
The varieties of the forests that exist in Sundarbans include mangrove scrub, littoral forest, saltwater mixed forest, brackish water mixed forest and swamp forest. Besides the forest, there are extensive areas of brackish water and freshwater marshes, intertidal mudflats, sandflats, sand dunes with typical dune vegetation, open grassland on sandy soils and raised areas supporting a variety of terrestrial shrubs and trees.
The Sundarbans is intersected by a complex network of tidal waterways, mudflats and small islands of salt-tolerant mangrove forests. The interconnected network of waterways makes almost every corner of the forest accessible by boat. The area is known for the Bengal tiger (Panthera tigris tigris), as well as numerous fauna including species of birds, spotted deer, crocodiles and snakes. The fertile soils of the delta have been subject to intensive human use for centuries, and the ecoregion has been mostly converted to intensive agriculture, with few enclaves of forest remaining. The remaining forests, taken together with the Sundarbans mangroves, are important habitat for the endangered tiger.
Additionally, the Sundarbans serves a crucial function as a protective barrier for the millions of inhabitants in and around Khulna and Mongla against the floods that result from the cyclones. The Sundarbans has also been enlisted among the finalists in the New7Wonders of Nature.
The physical development processes along the coast are influenced by a multitude of factors, comprising wave motions, micro and macro-tidal cycles and long shore currents typical to the coastal tract. The shore currents vary greatly along with the monsoon. These are also affected by cyclonic action. Erosion and accretion through these forces maintains varying levels, as yet not properly measured, of physiographic change whilst the mangrove vegetation itself provides a remarkable stability to the entire system. During each monsoon season almost all the Bengal Delta is submerged, much of it for half a year. The sediment of the lower delta plain is primarily adverted inland by monsoonal coastal setup and cyclonic events. One of the greatest challenges people living on the Ganges Delta may face in coming years is the threat of rising sea levels caused mostly by subsidence in the region and partly by climate change.
In a study conducted in 2012, the Zoological Society of London (ZSL) found out that the Sunderban coast was retreating up to 200 metres (660 ft) in a year. Agricultural activities had destroyed around 17,179 hectares (42,450 acres) of mangroves within three decades (1975–2010). Shrimp cultivation had destroyed another 7,554 hectares (18,670 acres). The rising sea levels had also submerged around 7,500 hectares (19,000 acres) of forest areas. This, coupled with an around 1.5 °C (2.7 °F) rise in surface water temperatures and increased levels of salinity have posed a problem for the survival of the indigenous flora and fauna. The Sundari trees are exceptionally sensitive to salinity and are being threatened with extinction.
A 2015 ethnographic study, conducted by a team of researchers from Heiderberg university in Germany, found a crisis brewing in the Sunderbans. The study contended that poor planning on the part of the India and Bangladesh governments coupled with natural ecological changes were forcing the flight of human capital from the region.
Loss of the mangrove forest will result in the loss of the protective biological shield against cyclones and tsunamis. This may put the surrounding coastal communities at high risk. Moreover, the submergence of land mass have rendered up to 6,000 families homeless and around 70,000 people are immediately threatened with the same.
The Sundarbans is not only a natural asset for Bangladesh and India but also a global buffer for the earth’s environment which is essential to maintain the delicate balance of the ecosystem of earth. So we need to take effective measures to preserve the forest of Sundarbans and other forests around the world.