Sunderban Trees Photo
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Deforestation of Sundarban has a great negative impact on its ecosystem. In Sundarban, like many areas of the world, mangrove deforestation is contributing to fisheries declines, degradation of clean water supplies, salinization of coastal soils, erosion, and land subsidence, as well as the release of carbon dioxide into the atmosphere. With regard to the Sundarban, experts have sounded caution that destruction of the forest will not only affect the ecology but cause far reaching impacts on national economy and causing immense damage to the marine resources of the Bay of Bengal, still economically unexplored and unexploited by Bangladesh. The loss of the Sundarban would also expose the entire southwestern region of the country to frequent cyclones and tidal surges. Every year a good number of tidal surges hit Bangladesh's south and southwestern coastline and the Sundarban bears the brunt acting as a vital barrier against all such calamitous lashings of the nature to protect the country's southwestern coastlines including the regional towns and cities like Mongla and Khulna.
Large areas of the Sundarban mangroves have already been converted into paddy fields over the past two centuries, and more recently into shrimp farms. The Sundarban has been extensively exploited over centuries for timber, fish and prawns, fodder, or converted for paddy and aquaculture. While conservation efforts have focused on wildlife, particularly tiger, through creation of several sanctuaries and a biosphere reserve, reduced freshwater inflows are a serious threat as salinity is rising. Heritiera fomes(locally called Sundari), Nypa fruticans and Phoenix paludosa are declining rapidly. Other threats to biodiversity come from the growing human population, pollution, and a rise in sea level.
The regulation of river flows by a series of dams, barrages and embankments for diverting water upstream for various human needs and for flood control has caused large reduction in freshwater inflow and seriously affected the biodiversity because of an increase in salinity and changes in sedimentation. During the past three decades, although some attempts have been taken to protect this unique ecosystem, its biodiversity continues to be threatened by a growing human population that not only places pressure on its biological resources, but also impacts on the freshwater inflows from upstream areas especially for Indian activities. Oil exploration in coastal areas is also emerging as a new threat. Further threats arise from global climate change, especially sea level rise. The future of the Sundarban will depend upon the management of freshwater resources as much as on the conservation of its biological resources.
Two major factors will determine the future of the Sundarban mangroves and their biological diversity. First, the demand on freshwater resources is bound to grow as the human population in both countries continues to increase, resulting in the restriction of freshwater flows to the monsoon season when extensive floods occur in the eastern parts of India and in Bangladesh. The resultant increase in salinization and accretion of sediments may alter vegetation composition. Impacts on animal communities may also occur due to both, the direct effects of salinity and indirectly through food chain modifications caused by the alterations in the nature and amount of detritus available in the mangrove ecosystem. Therefore, it is the human response to the spatial and temporal variability in precipitation, and hence the freshwater availability, which will determine the water availability for sustaining the functions and values of the mangroves. The proposed plan of India for the inter-basin transfer of water through a river-linking program has already raised concern for the fate of the Sundarban and its rich biodiversity, as well as for the major parts of Bangladesh. Secondly, global climate change is expected to increase the average temperature and spatial-temporal variability in precipitation, as well as cause a rise in sea level (Ellison, 1994). The increase in temperature and variability in rainfall will put further pressure on freshwater resources and hence, alter the freshwater inflows to the mangroves. If precipitation declines in the Ganga-Brahmaputra basins it may lead to a further reduction in the availability of freshwater in the deltaic region. Some models of climate change also present an increased frequency of tropical cyclones and storm surges, which may cause further changes in freshwater-seawater interactions and hence affect the mangroves. Substantial areas of the Sundarban along the coast are expected to be inundated by seawater in this case, and the increased landward salinity intrusion would affect the biotic composition. Ultimately, the future of the Sundarban mangroves hinges upon the efficiency of managing the limited freshwater resources for meeting both human and environmental needs, coupled with effective adaptive responses to the added threats from climate change. However, the future sustainability of the Sundarban will be contingent upon political will of the Governments of India and Bangladesh and continued support from the International agencies in respect to protect this unique wildlife feature of the world.Far-reaching changes are taking place slowly but steadily in the Sundarban region for years together due to direct and indirect impact of human interventions which are affecting its delicate ecosystem. Although the role of such changes is not yet clearly visible, but is evident that it will influence wildlife populations and vegetation in the long term. Today, these negative and menacing impacts are threatening the existence of the mangrove ecosystem. Massive changes in both the adjacent agricultural lands and upstream areas with construction of polders, embankments or barrages are feared to have been generating fundamental changes in the hydrological regime of the Sundarban. Due to natural processes the role of the Sundarban to discharge the water of the Ganges and Brahmaputra catchments is decreasing as main waterways are shifting eastwards. As a result, the salinity of the Sundarban is increasing -- particularly in the western region. The total annual discharge is decreasing due to intensifying land use in the upstream. Further, the decision taken by India for the construction of a mega river-linking project to withdraw the water form the main stream will cause serious problem in supplying the freshwater to Sundarban which will destroy the mangrove ecosystem. Mangrove forests once covered three-fourths of the coastlines of tropical and sub-tropical countries. Today, less than 50 percent of that is surviving. And then again, of this remaining mangrove forests, over 50 percent has been degraded and not in good form. Greater and comprehensive protection measures should be taken in national and international level for maintaining the high quality mangrove forests with a large biodiversity-rich ecosystem like the beautiful forest ‘Sundarban’, a World’s Heritage Site.Urgent steps are necessary to stop and reverse the current trend of deforestation and loss of biodiversity in the Sundarbans Reserve Forest (SRF), which is under pressure from a growing number of users. SRF has to be managed by an institution capable of managing a multidimensional resource. In addition to increased financial resources, a significant improvement in the institutional capacity of the Forest Department (FD) and an improved management approach based on appropriate research, community participation, and scientific planning is necessary.
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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. To know details about the flora of sundarban click here
The results of four independent inventories undertaken over the past seventy years would seem to indicate that the overall volume per hectare has decreased. Moreover, closer analysis of three inventories undertaken in 1959, 1983 and 1996 indicate a marked reduction in total standing volume (expressed in millions of cubic metres) for the two principal species of economic importance, Sundri and Gewa. The following table highlights the dramatic decrease.
Volume per hectare and total standing volume as estimated by Forestal, ODA (now DIFD) and the Forest Resources Management Project (FRMP)
Source: Chaffey et al 1983 (ODA), Revilla et al 1998 (FRMP)
The reasons for the decline in Sundri, Heriteria fomes is twofold. First, as a valuable timber species with real commercial value, it has been subject to heavy exploitation, both legal and illegal. Second, subtle changes in the ecology of the area, notably increases in salinity and siltation have resulted in hostile anaerobic conditions in which the Sundri finds difficulty in healthy respiration. This has resulted in dieback whereby the tree is progressively defoliated from the top downwards.
The decline in Gewa, Excoecaria agallocha is largely attributable to harvesting of around 50,000 m3 per annum as feedstock to Khulna Newsprint Mill for the production of newsprint. Although the mill is scheduled to close, one line continues to operate.
In recognition of the importance to manage the forest resources in the SRF on a sustainable basis, the Forest Department imposed a logging moratorium in 1989 on all timber species except Gewa. Diseased Sundri is felled and cleared as part of a sanitation programme and of course illegal logging by fishermen and other collectors continues to have an impact.
The main list of sundarban trees are given below. To know details, click
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