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Time to check salinity intrusion in the Sundarbans

Mohammad Asrafur Rahman
SUNDARBAN Mangrove forest of Bangladesh covers an area of about 6017 sq. km which is 62 percent of its total area whereas other 38 percent is situated in the West Bengal province of India. The average elevation from the mean sea level varies between 0.9 and 2.1 m. The rise in sea level and availability of less fresh water particularly during winter will cause inland intrusion of saline water.
Wetlands played a significant role in the development of human society. The natural productivity of wetlands is an invaluable component of the environment This wetland consists of a large number of fluvial and tidal landscapes, features created by the three mighty rivers Ganges Brahmaputra and Meghna (GBM). Annually 2.3 billion tons of sediments are transported by the major rivers having a profound effect on the floodplains and the coastal regions. The mangroves between the GBM deltas are the only contiguous and largest coastal wetland system in the world. Considering the conservational value of the Sundarbans UNESCO has declared pan of the forest (1,397 sq km) a World Heritage Site in 1997 and also Ramsar site wetlands (601,700 ha)-the largest living wetlands in the world. Sundarbans is one of the oldest systematically managed mangroves in the world Evidence suggests that this largest contiguous mangrove forest in the world is under .stress and showing serious signs of
depletion over the past few decades.
The vegetation in the sundarbans have the pattern like: Sundri (Heritiera forms}-!} percent, Sundri-Gewa (Exocoeria agallocha}- 29 percent Gewa- 5 percent, Gewa-Sundri-15 percent, Goran (Cerops decandra}- Gewa 14 percent, Gewa-Goran 9 percent, Keora (Sonneratia apetala)-1 percent
It constitutes about 51 percent of the Reserved Forest estates in the country and earns about 41 percent of the forest revenue. It contributes about 45 percent of the total timber and fuel wood produced from the public forests. In addition, diversified non-wood forest products are also exploited from the Sundarbans. Approximately one million people earn their livelihood from the forest. As a shelterbelt, it protects the south-west part of the country against cyclonic storms and tidal surges which is directly evident from the Sidr hit resistance during the last November. The forest also
protects agricultural land in the coast against salt intrusion from the sea. From different available sources it is estimated that around 120,000 visitors visit the Sundarban world heritage site every year adding to country's revenue.
Our Sundarban is intersected by elaborated network of rivers, channels and creeks -- a water area of 175,600 ha comprising Passur, Sibsa and Raimongal. There are four estuaries and widths of these are about 10 km. namely Bangra, Kunga, Malancha and Raimongal estuaries. However, the data available from Bangladesh Water Development Board shows the fresh water discharges of Ganges river at the Hardinge Bridge point for the seven months of the dry season in Chart A.
Shafi Noor Islam and Albrecht Gnauck summarised their understanding in an international conference at the Warsaw Agricultural University, Poland as shown in
Chart B
The effects of salinity intrusion can be manifold, what is visible now like destruction of mangroves and alluring shrimp farming. It is putting the future of our mangrove wetlands ecosystem in doubt. The name Sundarbans is supposed to be derived from the name of the plant, Sundari. Now, nearly 95 percent of the root surface cannot absorb water and nutrients because of salinity. It is only about five percent of the root surface that does the work, endangering the life of the plant. It has been reported that about 45 million Sundri trees have been affected by top dying of which at least 20 million trees have been seriously affected. At this rate this species will be vanished within next 47 years. Now only 20 mangrove species are available out of 70. Large part (45%) of mangroves have already been disappeared. High salinity has brought about a biodiversity loss. Reduction of fish habitat and the tree-top dying process have become the major ailments. 12 species of plants and animals have already become extinct like Javan rhinoceros, Single horned rhinoceros, Water buffalo, Swamp deer, Mugger crocodile, Gaur and Hog deer.
Under the auspices of the present policy the current management plan was formulated in 1998 for the period 19982010 under the World Bank assisted Forest Resources Management Project. The Forest Act was revised in 2000. This follows the principle for sustainable resource
utilisation. However, the national wetlands policy which has been drafted by MoEF, is yet to be not implemented. The main features of this policy are:
maintenance of biodiversity; maintenance of ecosystems functions; promotion of economical development.
Till today there arc hardly any such studies which directly explain the cause of top dying as well as decline of Sundri from the
Sundarbans. However, suggestions made as to the cause has not been supported by detailed investigation before. So, detailed scientific study is obvious for forestry management regimes to help maintain the decline of ecological pollution in this largest natural- ecosystems, and wildlife habitats.
During the last 100 years the Sundarbans has lost many species of plants and animals. Therefore the community as whole may partici-
pate in the process of its management. preservation and improvement. Once home to around 450 rivers and canals, several of the water bodies in the Sundarbans have now dried up. The changes have drastically affected the once abundant population of crocodiles, only 200 of whom now remain in the forest, according to a study. Initiatives are needed to develop strategies for adequate management plan based on monitoring of
flora and fauna and water quality with co-operation and appreciation of local people and international community. To protect the mangrove wetlands ecosystems and endangered plant and animal species and their habitats, high water salinity have to be reduced by increasing sweet water input
Ganges water diversion and sharing is not just a geo-technopolitical issue, it is also a humanitarian problem. Interaction is needed between states where it is a common concern for wise use of Ganges water resources. The threat and causality' analysis should be carried out with participation of stakeholders of all level. The present single agency planning process should be modified to accommodate other natural resource management agencies such as the Bangladesh Water Development Board, the Department of Fisheries, the Department of Agriculture etc to prepare an integrated plan
Reducing substantial use of mangrove resources and establishing eco-tourisrn considering 350m buffer zone for tourists and shrimp fry’ collectors in the heritage site is of utmost importance. Action has to be taken for reforestation, restoration and development of the mangroves. An integrated planning and management tool based on GIS and a wetlands simulation model and water quality indicators should be developed.
Mahamnud Asrafur Rahman is pursuing higher stud es in forestry in Germany and UK.