The Sundarbans *
UNESCO World Heritage Site
Country	Bangladesh India (West Bengal)
Type	Natural
Criteria	ix, x
Reference	798
Region **	Asia
Inscription history
Inscription	1997 (21st Session)
* Name as inscribed on World Heritage List ** Region as classified by UNESCO

The Sundarbans (Bengali: সুন্দরবন, Shundorbôn) is the largest single block of tidal halophytic mangrove forest in the world.^[1] The Sunderbans is a UNESCO World Heritage Site covering parts of India and Bangladesh.

The Sundarbans National Park is a National Park, Tiger Reserve, and a Biosphere Reserve located in the Sundarbans delta in the Indian state of West Bengal. Sundarbans South and Sundarbans West are two protected forests in Bangladesh. This region is densely covered by mangrove forests, and is one of the largest reserves for the Bengal tiger.

Etymology[link]

The name Sundarban can be literally translated as "beautiful forest" in the Bengali language (Shundor, "beautiful" and bon, "forest"). The name may have been derived from the Sundari trees that are found in Sundarbans in large numbers. Alternatively, it has been proposed that the name is a corruption of Samudraban (Bengali: সমুদ্রবন Shomudrobôn "Sea Forest") or Chandra-bandhe (name of a primitive tribe). However, the generally accepted view is the one associated with Sundari trees.^[1]

History[link]

Village in a clearing of Sunderbans. Drawing by Frederic Peter Layard (1818-1891), after an original sketch of 1839

House in Sundarbans with a pond and rice fields, 2010

The history of the area can be traced back to 200–300 AD. A ruin of a city built by Chand Sadagar has been found in the Baghmara Forest Block. During the Mughal period, the Mughal Kings leased the forests of the Sundarbans to nearby residents. Many criminals took refuge in the Sundarbans from the advancing armies of Emperor Akbar. Many have been known to be attacked by Tigers^[2] Many of the buildings which were built by them later fell to hands of Portuguese pirates, salt smugglers and dacoits in the 17th century. Evidence of the fact can be traced from the ruins at Netidhopani and other places scattered all over Sundarbans.^[3] The legal status of the forests underwent a series of changes, including the distinction of being the first mangrove forest in the world to be brought under scientific management. The area was mapped first in Persian, by the Surveyor General as early as 1764 following soon after proprietary rights were confiscated from the Mughal Emperor Alamgir II by the British East India Company in 1757. As the British had no expertise or adaptation experience in mangrove forests. Systematic management of this forest tract started in the 1860s after the establishment of a Forest Department in the Province of Bengal, in British India. The management was entirely designed to extract whatever treasures were available, but labor and lower management mostly were staffed by locals^[4]

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 in 1875–76 under the Forest Act, 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 headquarter in Khulna, Bangladesh. The first management plan was written for the period 1893–98.^[5][6]

In 1911, it was described as a tract of waste country which had never been surveyed, nor had the census been extended to it. It then stretched for about 165 miles (266 km) from the mouth of the Hugli to the mouth of the Meghna river and was bordered inland by the three settled districts of the 24 Parganas, Khulna and Bakerganj. The total area (including water) was estimated at 6,526 square miles (16,902 km²). It was a water-logged jungle, in which tigers and other wild beasts abounded. Attempts at reclamation had not been very successful. The Sundarbans was everywhere intersected by river channels and creeks, some of which afforded water communication throughout the Bengal region both for steamers and for native boats.

Geography[link]

A Panaroma atop an observation post at Hiron Point Wild Life Sanctuary, Khulna Range, Bangladesh

The Sundarban forest lies in the vast delta on the Bay of Bengal formed by the super confluence of the 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. The forest covers 10,000 km². of which about 6,000 are in Bangladesh.^[7] It became inscribed as a UNESCO world heritage site in 1997. The Sundarbans is estimated to be about 4,110 km², of which about 1,700 km² is occupied by waterbodies in the forms of river, canals and creeks of width varying from a few meters to several kilometers.

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 eponymous Royal 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.

Physiography[link]

SPOT satellite image of Sundarbans, released by CNES

Landsat 7 image of Sundarbans, released by NASA Earth Observatory

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. Situated mostly in Bangladesh, a small portion of it lies in India. The Indian part of the forest is estimated to be about 19%, while the Bangladeshi part is 81%. 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 16,700 km². Now it has dwindled into about 1/3 of the original size. The total land area today is 4,143 km² (including exposed sandbars: 42 km²) and the remaining water area of 1,874 km² 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 (Wahid et al., 2002).

The Sundarbans along the Bay of Bengal has evolved over the millennia through natural deposition of upstream sediments accompanied by intertidal segregation. The physiography is dominated by deltaic formations that include innumerable drainage lines associated with surface and subaqueous levees, splays and tidal flats. There are also marginal marshes above mean tide level, tidal sandbars and islands with their networks of tidal channels, subaqueous distal bars and proto-delta clays and silt sediments. The Sundarbans' floor varies from 0.9 m to 2.11 m above sea level.^[8]

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 stabilize 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 interior parts of the mudflats are magnificent home of luxuriant mangroves.

Ecoregions[link]

Sundarbans features two ecoregions — "Sundarbans freshwater swamp forests" (IM0162) and "Sundarbans mangroves" (IM1406).^[9]

Sundarbans freshwater swamp forests[link]

The Sundarbans freshwater swamp forests are a tropical moist broadleaf forest ecoregion of Bangladesh. 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 an area of 14,600 square kilometers (5,600 sq mi) of the vast Ganges-Brahmaputra Delta, extending from the northern part of Khulna District and finishing at the mouth of the Bay of Bengal with scattered portions extending into India's West Bengal state. 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.^[10]

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 characterized 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.^[10]

Sundarbans Mangroves[link]

The Sundarbans Mangroves ecoregion on the coast forms the seaward fringe of the delta and is the world's largest mangrove ecosystem, with 20,400 square kilometers (7,900 sq mi) of area covered. The dominant mangrove species Heritiera fomes 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 species that make up the forest include Avicennia spp., Xylocarpus mekongensis, Xylocarpus granatum, Sonneratia apetala, Bruguiera gymnorrhiza, Cereops decandra, Aegiceras corniculatum, Rhizophora mucronata, and Nypa fruticans palms.^[11]

Climate change impact[link]

Sundarbans a few months after Cyclone Sidr

Mudflats in Sundarbans

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 advected 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 many of the Bangladesh's mangrove wetlands, freshwater reaching the mangroves was considerably reduced from the 1970s due to diversion of freshwater in the upstream area by neighboring India through the use of the Farakka Barrage bordering Rajshahi, Bangladesh. Also, the Bengal Basin is slowly tilting towards the east due to neo-tectonic movement, forcing greater freshwater input to the Bangladesh Sundarbans. As a result, the salinity of the Bangladesh Sundarbans is much lower than that of the Indian side. A 1990 study noted that there "is no evidence that environmental degradation in the Himalayas or a 'greenhouse' induced rise in sea level have aggravated floods in Bangladesh"; however, a 2007 report by UNESCO, "Case Studies on Climate Change and World Heritage" has stated that an anthropogenic 45-cm rise in sea level (likely by the end of the 21st century, according to the Intergovernmental Panel on Climate Change), combined with other forms of anthropogenic stress on the Sundarbans, could lead to the destruction of 75% of the Sundarbans mangroves.^[12] Already, Lohachara Island and New Moore Island/South Talpatti Island have disappeared under the sea, and Ghoramara Island is half submerged.^[13]

Flora[link]

Sundari tree (Heritiera littoralis)

Golpata (Nypa fruticans)

A total 245 genera and 334 plant species were recorded by David Prain in 1903.^[14] While most of the mangroves in other parts of the world are characterized by members of the Rhizophoraceae, Avicenneaceae or Laganculariaceae, the mangroves of Bangladesh are dominated by the Sterculiaceae and Euphorbiaceae.^[5] Dominant flora includes:

The Sundarbans flora is characterized by the abundance of sundari (Heritiera fomes), gewa (Excoecaria agallocha), goran (Ceriops decandra) and keora (Sonneratia apetala) all of which occur occur prominently throughout the area. The characteristic tree of the forest is the sundari (Heritiera littoralis), from which the name of the forest had probably been derived. It yields a hard wood, used for building houses and making boats, furniture and other things. New forest accretions is often conspicuously dominated by keora (Sonneratia apetala) and tidal forests. It is an indicator species for newly accreted mudbanks and is an important species for wildlife, especially spotted deer (Axis axis). There is abundance of dhundul or passur (Xylocarpus granatum) and kankra (Bruguiera gymnorrhiza) though distribution is discontinuous. Among palms, Poresia coaractata and Myriostachya wightiana, and among grasses spear grass (Imperata cylindrica), khagra (Phragmites karka) and golpata (Nypa fruticans) are well distributed.

The varieties of the forests that exist in Sunderbans 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. Since Prain’s report there have been considerable changes in the status of various mangrove species and taxonomic revision of the man-grove flora.^[15] 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 colonization on new accretions to more mature beach forests. Historically vegetation types have been recognized in broad correlation with varying degrees of water salinity, freshwater flushing and physiography.

Mangrove[link]

Twenty-six of the fifty broad mangrove types found in the world grow well in the Sundarbans. The commonly identifiable vegetation that grow in the dense mangrove forests at the Sundarbans 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[link]

Ecological succession is generally defined as the successive occupation of a site by different plant communities.^[16] 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.^[17] Troup suggested that succession began in the newly accreted land created by fresh deposits of eroded soil.^[18] 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.

Fauna[link]

Chital deers (Axis axis) are widely seen

A Rhesus Macaque (Macaca mulatta)

The Sundarbans provides a unique ecosystem and a rich wildlife habitat. According to the 2011 tiger census, the Sundarbans have about 270 tigers. Although previous rough estimates had suggested much higher figures close to 300, the 2011 census provided the first ever scientific estimate of tigers from the area^[19][20] Tiger attacks are frequent in the Sundarbans. Between 100 and 250 people are killed per year.

There is much more wildlife here than just the endangered Royal Bengal Tiger (Panthera tigris tigris). Most importantly, mangroves are a transition from the marine to freshwater and terrestrial systems, and provide critical habitat for numerous species of small fish, crabs, shrimps and other crustaceans that adapt to feed and shelter, and reproduce among the tangled mass of roots, known as pneumatophores, which grow upward from the anaerobic mud to get the supply of oxygen. Fishing Cats, Macaques, wild boars, Common Grey Mongooses, Foxes, Jungle Cats, Flying Foxes, Pangolins, and spotted deer are also found in abundance in the Sundarbans.

A 1991 study has revealed that the Bangladeshi part of the Sundarbans supports diverse biological resources including at least 150 species of commercially important fishes, 270 species of birds, 42 species of mammals, 35 reptiles and 8 amphibian species. This represents a significant proportion of the species present in Bangladesh (i.e. about 30% of the reptiles, 37% the birds and 34% of the mammals) and includes a large number of species which are now extinct elsewhere in the country.^[21] Two amphibians, 14 reptiles, 25 aves and five mammals are presently endangered.^[22] The Sundarbans is an important wintering area for migrant water birds^[23] and is an area suitable for watching and studying avifauna.^[24]

The management of wildlife is presently 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^[5] and the Sundarbans has not been spared from this decline, the mangrove forest retains several good wildlife habitats and their associated fauna. Of these, the tiger and dolphin are target species for planning wildlife management and tourism development. There are high profile and vulnerable mammals living in two contrasting environments, and their statuses and management are strong indicators of the general condition and management of wildlife. Some of the species are protected by legislation, notably by the Bangladesh Wildlife (Preservation) Order, 1973 (P.O. 23 of 1973).^[25]

Predators[link]

A Bengal tiger (Panthera tigris tigris)

A saltwater crocodile (Crocodylus porosus) in Sundarbans

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, together with the Sundarbans mangroves, are important habitats for the endangered Bengal Tiger (Panthera tigris). The forest also contains leopard (Panthera pardus fusca) and several other smaller predators such as the jungle cats (Felis chaus), fishing cats (Prionailurus viverrinus), and leopard cats (Prionailurus bengalensis).^[10]

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 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 boars (Sus scrofa), and even Rhesus Macaque (Macaca mulatta). It is estimated that there are now 500^[20] Bengal tigers and about 30,000 spotted deer in the area. The tigers regularly attack and kill humans who venture into the forest, human deaths ranging from 30–100 per year.^[26]

Some of the reptiles are predators too, including two species of crocodiles, the Saltwater Crocodile (Crocodylus porosus) and Mugger crocodile (Crocodylus palustris), as well as the Gharial (Gavialis gangeticus) and the Water monitor lizards (Varanus salvator), all of which hunt on both land and water. Sharks and the Gangetic dolphins (Platanista gangetica) roam the waterways.^[27]

Avifauna[link]