Сундарбан: крупнейший мангровый лес в дельте Ганга и Брахмапутры

Mangrove forest in the Bay of Bengal

Sundarbans (pronounced /s//ʌ//n//'//d//ɑːr//b//ə//n//z/) is a mangrove area in the delta formed by the confluence of the Ganges, Brahmaputra and Meghna Rivers in the Bay of Bengal. Spread across parts of India and Bangladesh, this forest is the largest mangrove forest in the world. It spans the area from the Baleswar River in Bangladesh's division of Khulna to the Hooghly River in India's state of West Bengal. It comprises closed and open mangrove forests, land used for agricultural purpose, mudflats and barren land, and is intersected by multiple tidal streams and channels. Sundarbans is home to the world's largest area of mangrove forests. Four protected areas in the Sundarbans are enlisted as UNESCO World Heritage Sites, viz. Sundarbans West (Bangladesh), Sundarbans South (Bangladesh), Sundarbans East (Bangladesh) and Sundarbans National Park (India). Despite the protected status, the Indian Sundarbans were considered endangered in a 2020 assessment under the IUCN Red List of Ecosystems framework. The Sundarbans mangrove forest covers an area of about , of which forests in Bangladesh's Khulna Division extend over and in West Bengal's Presidency division, they extend over across the South 24 Parganas and North 24 Parganas districts. The most abundant tree species are sundri (Heritiera fomes) and gewa (Excoecaria agallocha). The forests provide habitat to 453 fauna wildlife, including 290 bird, 120 fish, 42 mammal, 35 reptile and eight amphibian species. Despite a total ban on all killing or capture of wildlife other than fish and some invertebrates, there has been a consistent pattern of depleted biodiversity or loss of species in the 20th century, with the ecological quality of the forest declining. Despite preservation commitments from both governments, the Sundarbans are under threat from both natural and human made causes. In 2007, the landfall of Cyclone Sidr damaged around 40% of the Sundarbans. The forest is also suffering from increased salinity caused by sea level rise due to effects of climate change and reduced freshwater supply. In May 2009, Cyclone Aila devastated the Sundarbans with massive casualties. At least 100,000 people were affected by this cyclone. The proposed coal fired Rampal power station situated north of the Sundarbans at Rampal Upazila of Bagerhat District in Khulna, Bangladesh, is anticipated to further damage this unique mangrove forest according to a 2016 report by UNESCO. Climate change is expected to continue to negatively affect both natural systems and human populations in the region, resulting in further ecosystem degradation and climate migration. Experts examining the region recommend further focus on mangrove restoration and management and advocating for adaptation of human populations, through processes like managed retreat and investments in resilient infrastructure.

The literal meaning of Sundarbans is "beautiful forest". Alternatively, it was proposed that the name is a corruption of Samudraban, Shomudrobôn ("Sea Forest"), or Chandra bandhe, the name of a tribe. However, the likely origin of the word is Sundari or Sundri, the local name of the mangrove species Heritiera fomes abundant in the area.

The history of human settlement in the Sundarbans area can be traced back to Mauryan era (4th 2nd century BCE). A ruin of an abandoned city was found in the Baghmara Forest Block that is attributed to Chand Sadagar, a pre Mauryan semi historical figure in Bengali folklore. During the Mughal period, forest tracts were leased out by the local rulers for establishing settlements. In 1757, The British East India Company obtained proprietary rights over Sundarbans from the Mughal Emperor Alamgir II and completed mapping the area in 1764. However, systematic forest management started a century later. The first Forest Management Division to have jurisdiction over the Sundarbans was established in 1869. In 1875 a large portion of the mangrove forests was declared as reserved forests under the Indian Forest Act of 1865 (Act VIII of 1865). The remaining portions of the forests were declared a reserve forest the following year and the forest, which was so far administered by the civil administration district, was placed under the control of the Forest Department. A Forest Division, which is the basic forest management and administration unit, was created in 1879 with the headquarters in today Khulna, Bangladesh. The first management plan was written for the period 1893–1898.

The Sundarban forest lies in the vast delta on the Bay of Bengal formed by the super confluence of the Hooghly, Padma (both are distributaries of Ganges), Brahmaputra and Meghna rivers across southern Bangladesh. The seasonally flooded Sundarbans freshwater swamp forest lies inland from the mangrove forests on the coastal fringe. The forest covers of which about are in Bangladesh. The Indian part of Sundarbans is estimated to be about , of which about is occupied by water bodies in the forms of river, canals and creeks of width varying from a few metres to several kilometres.

The mangrove dominated Ganges Delta – the Sundarbans – is a complex ecosystem comprising one of the three largest single tracts of mangrove forests of the world. The larger part is situated in Bangladesh, a smaller portion of it lies in India. The Indian part of the forest is estimated to be about 40 percent, while the Bangladeshi part is 60 percent. To the south the forest meets the Bay of Bengal; to the east it is bordered by the Baleswar River and to the north there is a sharp interface with intensively cultivated land. The natural drainage in the upstream areas, other than the main river channels, is everywhere impeded by extensive embankments and polders. The Sundarbans was originally measured (about 200 years ago) to be of about Now it has dwindled into about one third of its original size. The total land area today is , including exposed sandbars with a total area of ; the remaining water area of encompasses rivers, small streams and canals. Rivers in the Sundarbans are meeting places of salt water and freshwater. Thus, it is a region of transition between the freshwater of the rivers originating from the Ganges and the saline water of the Bay of Bengal. Biotic factors here play a significant role in physical coastal evolution, and for wildlife a variety of habitats have developed which include beaches, estuaries, permanent and semi permanent swamps, tidal flats, tidal creeks, coastal dunes, back dunes and levees. The mangrove vegetation itself assists in the formation of new landmass and the intertidal vegetation plays a significant role in swamp morphology. The activities of mangrove fauna in the intertidal mudflats develop micromorphological features that trap and hold sediments to create a substratum for mangrove seeds. The morphology and evolution of the eolian dunes is controlled by an abundance of xerophytic and halophytic plants. Creepers, grasses and sedges stabilise sand dunes and uncompacted sediments. The Sunderbans mudflats (Banerjee, 1998) are found at the estuary and on the deltaic islands where low velocity of river and tidal current occurs. The flats are exposed in low tides and submerged in high tides, thus being changed morphologically even in one tidal cycle. The tides are so large that approximately one third of the land disappears and reappears every day. The interior parts of the mudflats serve as a perfect home for mangroves.

Sundarbans features two ecoregions — "Sundarbans freshwater swamp forests" (IM0162) and "Sundarbans mangroves" (IM1406).

The Sundarbans freshwater swamp forests are a tropical moist broadleaf forest ecoregion of Bangladesh and India. It represents the brackish swamp forests that lie behind the Sundarbans Mangroves, where the salinity is more pronounced. The freshwater ecoregion is an area where the water is only slightly brackish and becomes quite fresh during the rainy season, when the freshwater plumes from the Ganges and the Brahmaputra rivers push the intruding salt water out and bring a deposit of silt. It covers of the vast Ganges Brahmaputra Delta, finishing at the mouth of the Bay of Bengal from the northern part of Khulna District and the southern part of North 24 Parganas district in the Indian state of West Bengal. The Sundarbans freshwater swamp forests lie between the upland Lower Gangetic plains moist deciduous forests and the brackish water Sundarbans mangroves bordering the Bay of Bengal. A victim of large scale clearing and settlement to support one of the densest human populations in Asia, this ecoregion is under a great threat of extinction. Hundreds of years of habitation and exploitation have exacted a heavy toll on this ecoregion's habitat and biodiversity. There are two protected areas – Narendrapur (110 km2) and Ata Danga Baor (20 km2) that cover a mere 130 km2 of the ecoregion. Habitat loss in this ecoregion is so extensive, and the remaining habitat is so fragmented, that it is difficult to ascertain the composition of the original vegetation of this ecoregion. According to Champion and Seth (1968), the freshwater swamp forests are characterised by Heritiera minor, Xylocarpus molluccensis, Bruguiera conjugata, Sonneratia apetala, Avicennia officinalis, and Sonneratia caseolaris, with Pandanus tectorius, Hibiscus tiliaceus, and Nipa fruticans along the fringing banks. 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.

Ecological succession is generally defined as the successive occupation of a site by different plant communities. In an accreting mudflats the outer community along the sequence represents the pioneer community which is gradually replaced by the next community representing the seral stages and finally by a climax community typical of the climatic zone. Robert Scott Troup suggested that succession began in the newly accreted land created by fresh deposits of eroded soil. The pioneer vegetation on these newly accreted sites is Sonneratia, followed by Avicennia and Nypa. As the ground is elevated as a result of soil deposition, other trees make their appearance. The most prevalent, though one of the late species to appear, is Excoecaria. As the level of land rises through accretion and the land is only occasionally flooded by tides, Heritiera fomes begins to appear.

A total of 245 genera and 334 plant species were recorded by David Prain in 1903. While most of the mangroves in other parts of the world are characterised by members of the Rhizophoraceae, Avicenneaceae or Combretaceae, the mangroves of Bangladesh are dominated by the Malvaceae and Euphorbiaceae. However, very little exploration of the botanical nature of the Sundarbans has been made to keep up with these changes. Differences in vegetation have been explained in terms of freshwater and low salinity influences in the Northeast and variations in drainage and siltation. The Sundarbans has been classified as a moist tropical forest demonstrating a whole mosaic of seres, comprising primary colonisation on new accretions to more mature beach forests. Historically vegetation types have been recognised in broad correlation with varying degrees of water salinity, freshwater flushing and physiography.

The Sundarbans provides a unique ecosystem and a rich wildlife habitat. According to the 2015 tiger census in Bangladesh, and the 2011 tiger census in India, the Sundarbans have about 180 tigers (106 in Bangladesh and 74 in India). Earlier estimates, based on counting unique pugmarks, were much higher. The more recent counts have used camera traps, an improved methodology that yields more accurate results. Tiger attacks were historically common in the area, and are still frequent in the Sundarbans, with around 40 people killed in 2000–2010. Two amphibians, 14 reptiles, 25 aves and five mammals are endangered. and is an area suitable for watching and studying avifauna. The management of wildlife is restricted to, firstly, the protection of fauna from poaching, and, secondly, designation of some areas as wildlife sanctuaries where no extraction of forest produce is allowed and where the wildlife face few disturbances. Although the fauna of Bangladesh have diminished in recent times

The Sundarbans are an important habitat for the Bengal tiger (Panthera tigris). The forest also provides habitat for small wild cats such as the jungle cat (Felis chaus), fishing cat (Prionailurus viverrinus), and leopard cat (P. bengalensis). Several predators dwell in the labyrinth of channels, branches, and roots that poke up into the air. This is the only mangrove ecoregion that harbors the Indo Pacific region's largest terrestrial predator, the Bengal tiger. Unlike in other habitats, tigers live here and swim among the mangrove islands, where they hunt scarce prey such as the chital deer (Axis axis), Indian muntjacs (Muntiacus muntjak), wild boar (Sus scrofa), and Rhesus macaque (Macaca mulatta). It is estimated that there are now 180 Bengal tigers

Forest inventories reveal a decline in standing volume of the two main commercial mangrove species – sundari (Heritiera spp.) and gewa (Excoecaria agallocha) — by 40% and 45% respectively between 1959 and 1983. Some species such as hog deer (Axis porcinus), water buffalos (Bubalus bubalis), barasingha or swamp deer (Cervus duvauceli), Javan rhinoceros (Rhinoceros sondaicus), Indian rhinoceros (Rhinoceros unicornis) and the mugger crocodile (Crocodylus palustris) started to become extinct in the Sundarbans towards the middle of the 20th century, because of extensive poaching and hunting by the British and locals. There are other threatened mammal species, such as the capped langur (Semnopithecus pileatus), smooth coated otter (Lutrogale perspicillata), Asian small clawed otter (Aonyx cinerea) and large Indian civet (Viverra zibetha).

According to a report created by UNESCO, the landfall of Cyclone Sidr damaged around 40% of Sundarbans in 2007.

In August 2010, a memorandum of understanding was signed between Bangladesh Power Development Board (BPDB) and India's state owned National Thermal Power Corporation (NTPC) where they designated to implement the coal fired Rampal power station by 2016. The proposed project, on an area of over 1,834 acres of land, is situated north of the Sundarbans. This project violates the environmental impact assessment guidelines for coal based thermal power plants. Environmental activists contend that the proposed location of the Rampal Station would violate provisions of the Ramsar Convention. The government of Bangladesh rejected the allegations that the coal based power plant would adversely affect the world's largest mangrove forest. On 9 December 2014 an oil tanker named Southern Star VII, of Sundarbans after it had been hit by a cargo vessel. The oil spread over area after the clash, as of 17 December. The slick spread to a second river and a network of canals in the Sundarbans and blackened the shoreline. The event was very threatening to trees, plankton, and vast populations of small fishes and dolphins. The event occurred at a protected Sundarbans mangrove area, home to the rare Irrawaddy and Ganges dolphins. Until 15 December 2014 only of oil from the area had been cleaned up by local residents, the Bangladesh Navy, and the government of Bangladesh. Some reports indicated that the event killed some wildlife.

The Sundarbans plays an important role in the economy of the southwestern region of Bangladesh as well as in the national economy. It is the single largest source of forest produce in the country. The forest provides raw materials for wood based industries. In addition to traditional forest produce like timber, fuelwood, pulpwood etc., large scale harvest of non wood forest products such as thatching materials, honey, beeswax, fish, crustacean and mollusc resources of the forest takes place regularly. The vegetated tidal lands of the Sundarbans function as an essential habitat, produces nutrients and purifies water. The forest also traps nutrient and sediment, acts as a storm barrier, shore stabiliser and energy storage unit. Last but not the least, the Sunderbans provides an aesthetic attraction for local and foreign tourists. The water houseboat in the Sundarbans is also a recent attraction among the tourists. The forest has immense protective and productive functions. Constituting 51% of the total reserved forest estate of Bangladesh, it contributes about 41% of total forest revenue and accounts for about 45% of all timber and fuel wood output of the country.

The Sundarbans has a population of over 4 million but much of it is mostly free of permanent human habitation. Despite human habitations and a century of economic exploitation of the forest well into the late 1940s, the Sundarbans retained a forest closure of about 70% according to the Overseas Development Administration (ODA) of the United Kingdom in 1980.

The Sundarbans area is one of the most densely populated areas in the world, and the population is increasing. As a result, half of this ecoregion's mangrove forests have been cut down to supply fuelwood and other natural resources. Despite the intense and large scale exploitation, this still is one of the largest contiguous areas of mangroves in the world. Another threat comes from deforestation and water diversion from the rivers inland, which causes far more silt to be brought to the estuary, clogging up the waterways. The Directorate of Forest is responsible for the administration and management of Sundarban National Park in West Bengal. The Principal Chief Conservator of Forests (PCCF), Wildlife & Bio Diversity & ex officio Chief Wildlife Warden, West Bengal is the senior most executive officer looking over the administration of the park. The Chief Conservator of Forests (South) & Director, Sundarban Biosphere Reserve is the administrative head of the park at the local level and is assisted by a Deputy Field Director and an Assistant Field Director. The park area is divided into two ranges, overseen by range forest officers. Each range is further sub divided into beats. The park also has floating watch stations and camps to protect the property from poachers. The park receives financial aid from the State Government as well as the Ministry of Environment and Forests under various Plan and Non Plan Budgets. Additional funding is received under the Project Tiger from the Central Government. In 2001, a grant of US$20,000 was received as a preparatory assistance for promotion between India and Bangladesh from the World Heritage Fund. A new Khulna Forest Circle was created in Bangladesh back in 1993 to preserve the forest, and Chief Conservators of Forests have been posted since. The direct administrative head of the Division is the Divisional Forest Officer, based at Khulna, who has a number of professional, subprofessional and support staff and logistic supports for the implementation of necessary management and administrative activities. The basic unit of management is the compartment. There are 55 compartments in four Forest Ranges and these are clearly demarcated mainly by natural features such as rivers, canals and creeks. Recently West Bengal Cabinet has approved a new district in South 24 Parganas and proposed district was named Sundarban.

The Bangladesh part of the forest lies under two forest divisions, and four administrative ranges viz Chandpai (Khulna District), Sarankhola (Khulna), and Burigoalini (Satkhira District) and has sixteen forest stations. It is further divided into fifty five compartments and nine blocks.

Sundarbans East Wildlife Sanctuary extends over an area of in Bangladesh. Sundari trees (Heritiera fomes) dominate the flora, interspersed with Gewa (Excoecaria agallocha) and Passur (Xylocarpus mekongensis) with Kankra (Bruguiera gymnorhiza) occurring in areas subject to more frequent flooding. There is an understory of Shingra (Cynometra ramiflora) where, soils are drier and Amur (Aglaia cucullata) in wetter areas and Goran (Ceriops decandra) in more saline places. Nypa palm (Nypa fruticans) is widespread along drainage lines.

Sundarbans South Wildlife Sanctuary extends over an area of in Bangladesh. There is evidently the greatest seasonal variation in salinity levels and possibly represents an area of relatively longer duration of moderate salinity where Gewa (Excoecaria agallocha) is the dominant woody species. It is often mixed with Sundri, which is able to displace in circumstances such as artificially opened canopies where Sundri does not regenerate as effectively. It is also frequently associated with a dense understory of Goran (Ceriops tagal) and sometimes Passur.

Sajnakhali Wildlife Sanctuary is a area in the northern part of the Sundarbans delta in South 24 Parganas district, West Bengal, India. It is mainly mangrove scrub, forest and swamp. It was set up as a sanctuary in 1976. It is home to a rich population of different species of wildlife, such as water fowl, heron, pelican, spotted deer, rhesus macaques, wild boar, tigers, water monitor lizards, fishing cats, otters, olive ridley turtles, crocodiles, batagur terrapins, and migratory birds.

The Sundarbans is celebrated through numerous Bengali folk songs and dances, often centred around the folk heroes, gods and goddesses specific to the Sunderbans (like Bonbibi and Dakshin Rai) and to the Lower Gangetic Delta (like Manasa and Chand Sadagar). The Bengali folk epic Manasamangal mentions Netidhopani and has some passages set in the Sundarbans during the heroine Behula's quest to bring her husband Lakhindar back to life. The area provides the setting for several novels by Emilio Salgari, (e. g. The Mystery of the Black Jungle). Sundarbaney Arjan Sardar, a novel by Shibshankar Mitra, and Padma Nadir Majhi, a novel by Manik Bandopadhyay, are based on the rigors of lives of villagers and fishermen living in the Sunderbans region, and are woven into the Bengali psyche to a great extent. Part of the plot of Salman Rushdie's Booker Prize winning novel Midnight's Children is set in the Sundarbans. This forest is adopted as the setting of Kunal Basu's short story "The Japanese Wife" and the subsequent film adaptation. Most of the plot of an internationally acclaimed novelist, Amitav Ghosh's 2004 novel, The Hungry Tide, is set in the Sundarbans. The plot centres on a headstrong American cetologist who arrives to study a rare species of river dolphin, enlisting a local fisherman and translator to aid her. The book also mentions two accounts of the Bonbibi story of "Dukhey's Redemption". Manik Bandopadhyay's Padma Nadir Majhi was made into a movie by Goutam Ghose. The Sunderbans has been the subject of a detailed and well researched scholarly work on Bonbibi (a 'forest goddess' venerated by Hindus), on the relation between the islanders and tigers and on conservation and how it is perceived by the inhabitants of the Sundarbans, as well as numerous non fiction books, including The Man Eating Tigers of Sundarbans by Sy Montegomery for a young audience, which was shortlisted for the Dorothy Canfield Fisher Children's Book Award. In Up The Country, Emily Eden discusses her travels through the Sunderbans. Numerous documentary movies have been made about the Sunderbans, including the 2003 IMAX production Shining Bright about the Bengal tiger. The acclaimed BBC TV series Ganges documents the lives of villagers, especially honey collectors, in the Sundarbans.