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Ecology of Sundarban, Bangladesh

M R Rahman
Institute of Environmental Science, University of Rajshahi, Rajshahi-6205, Bangladesh

M Asaduzzaman
Executive Director. Bangladesh Science Foundation, Dhaka, Bangladesh.

Abstract/ Executive Summary:

Sundarban is the largest mangrove wetland in the world. It covers an area of about 1mha, of which 60% is located in Bangladesh and the remaining western portion, comprising 40%, lies in India. Mangrove ecosystems are of great ecological significance in the tropical and sub-tropical coast. They protect our coast from heavy wind, tidal waves, coastal erosion and sea water intrusion, generate substantial quantities of fishery resources and provide many useful forestry products. The Sundarban ecosystem supports rich fisheries diversity. This ecosystem support 27 families and 53 species of pelagic fish, 49 families 124 species of demersal fish, 5 families and 24 species of shrimps, 3 families and 7 species of crabs, 8 species of lobster. A total 334 plants, 165 algal, 13 special orchids, 17 fern, 87 monocotyledon and 230 dicotyledon belonging to 245 genera and 75 families from the sundarbans and adjacent area are found available. The principal tree species is Sundry (Heritiera fomes) which covers about 73% to total landmass and the second species is Gewa (Excoecaria agallocha) which covers about 16% of total forest area. The plant species include 35 legumes, 29 grasses, 19 sedges, and 18 euphorbias. Of the 50 true mangrove plant species recorded throughout the globe, the Sundarbans alone contain 35 species. The magnificent among the animals on land is Royal Bengal Tiger, Spotted deer, barking deer and wild boars are there in plenty. Besides those jungle cats, fishing cat, civet cat, monkey, bengal fox, jackle, water monitor, monitor lizard and snakes are important faunal spp. Moreover, abundant of the Sundarbans are purple heron, pond heron, cattle egret, little egret, open billed stork, smaller adjutant stork, brahmini kite, spotted dove, rose ringed parakeet, crow pheasant, wood pecker, bee eater, drongo, pide myna, jungle myna, bulbul, tailor bird, magpie robin, sparrow etc., Otherwise, recorded that wild Buffalo, 2 species of deer, javan rhinoceros extinct and presently 2 species of amphibians, 14 species of reptiles 25 species of birds and 5 species of mammals are considered as endangered species. This paper is to produce a new assessment of the mangroves ecology of Sundarbans.

Keywords: Ecology, Sundarbans, Bangladesh

Location: Sundarban,Khulna

Start Date:

End Date:

Program Area: Conservation and Biodiversity

Non-commodity: Analysis and interpretations

Objectives:

The main objective of this paper is to assess the existing conditions of ecosystem, biodiversity, causes of loss of natural resources, salinity intrusion and other related factors.

Methodology:

Most of the data were collected from secondary sources. All previous data and reports were collected from forest department of Khulna and Dhaka and internet web pages. For collecting primary data six categories of questionnaires have been used. The set of questionnaires have been designed to be used by the officials like divisional forest officers, range officers, deputy forest rangers, and forest rangers etc of the forest department tasked with overseeing the sundarban forest; the second set of questionnaire have been made to be used by the employees like forester, guard and boatman etc.; the third, by the wood cutters, the fourth, by the bawali (people involved in collecting goal patta); the fifth, by the mawali (people involved in honey and wax extractions); and the sixth, by the local people. To produce some statistics at a (i.e. at a relatively small scale), the classification system had to be simplified, hence the priority was to discriminate from space and to delineate the following classes: dense (tall or low) mangroves (including unexplained top dying), degraded mangrove or young stands, very degraded mangrove or young stages, mangrove afforestation areas, active deforestation activities (hot spots) and mangrove areas converted to other uses. Dense mangroves- the canopy is dense and evergreen; such an ecosystem or group of ecosystems is hardly subject to visible degradation processes, from space. This class includes, in the sunderban, an area which corresponds to an unexplained mortality of some mangrove trees (Heritiera fomes). Degraded and very degraded mangrove stages-this is a broad class in which most degraded stages are grouped, although at a local or a national levels, additional distinctions would be needed. Mangrove afforestation areas -this extremely ambitious coastal management activity is commented in the section related to the sundarban. Active deforestation activity (or hot spots)- deforestation and wood extraction are major causes, yet poorly documented, of mangrove depletion in many parts of the world. Monitoring activities are to be focused mainly on those areas where active deforestation 37 practices were observed and should be considered as ‘hot spots’ for the survival of rare plant communities. Methods of studding Mangroves Data to be collected and processed in the following steps-the study site will be selected using GPS, transact line is perpendicular to the shoreline, the plot dimension is 10m x 10m, within each plot counts are made for tree counts and in 1m × 1m sub plot counts are made for seedling and sapling, counting the numbers of three class of maturity viz., trees, sapling and seedling by species within the plot, sapling between 1-4m and seedling below 1m are counted species wise for numbers. Densities is measured species wise and total in each plot as follows, density of each species (no/ha)= no. × 10,000 m² /area of plot in m² and total density of all species=sum of all species densities.

Source of Information: J. Sci. Foundation, 8(1&2): 35-47, June-December 2010, ISSN 1728-7855

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The ecology of the mangrove wetlands is influenced by a number of macro-level physical forces. Among them, the quantity and periodicity of freshwater flow plays a significant role in determining the species diversity, biomass and forest structure. This is especially important for river-dominated mangrove wetlands since the flora of these mangrove wetlands is more susceptible to reduction in freshwater flow than tide-dominated mangrove wetlands. Secondly, species selection for plantation or restoration of degraded mangroves needs to be based on the currently available species. Any attempt to reintroduce the low-saline species that were lost from a mangrove wetland might not succeed without increasing the freshwater flow. For example, attempts to reintroduce Son- neratia apetala, Xylocarpus granatum and Bruguiera gymnorhiza in the Pichavaram and Muthupet mangrove wetlands failed because of high soil salinity. Thirdly, river-dominated mangroves characterized by high nutrient influx and strong out-welling from mangrove forests, play a significant role in maintaining the fishery production of the adjacent coastal waters. Hence, reduction in freshwater flow would affect the amount of nutrient exported to coastal environment and thereby affect fishery production. Thus, in order to save the current floral diversity and biomass of the mangrove wetlands as well as fishery production of the adjacent coastal waters, prevention of further reduction in freshwater inflow into the mangrove wetlands should be one of the main objectives of mangrove conservation and management plans.

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