Ecologically
Important Areas in West Bengal:
Institute
for Ocean Management has identified the Sundarbans delta under the category of
Ecologically Important Areas in the state of West Bengal.
Geographic
Location of West Bengal
Coast
The
state of West Bengal extends from the Himalayas to the Bay of Bengal. It has a
varied climate and forestry ranging from temperate on the Himalayas to hot in
the mangrove swamps at the estuaries providing habitat for an equally varied flora
and fauna. The state has a coastline of 210 km. Midnapore coast is characterized
by sand dunes, long shore currents, minor river discharges, less turbid but high
saline sea water influence, cuspate delta of the subarnarekha, and neotectonic
depressions in the west. The Sunderbans in the South-24 Parganas have an intricate
coastline, clusters of deltas with interlinked channels, creeks, and estuaries.
Deltaic regions are mostly clayey due to high deposit of sediments (8million tones/yr)
through the Hooghly system. A clayey blanket covering gravels of sandstone, siltstone,
and quartz indicate quaternary age of the area. A neotectonic and morphogenic
tilt between 12th and 16th century resulted in an uplift of the western part of
the Ganga towards the Padma and hastened the deltaic formation. Consequently,
West Bengal does not receive the fertile alluvium as before and the terrain is
not de-salinated by river floods. The beaches and inlets, creeks, and mangrove
swamps, mudflats, coastal dunes and sand flats are the characteristics of the
area.
Fig: Showing
the Ecologically Important Area in West Bengal
click
on the location for details
The
most important climatic factor is the high frequency of violent cyclonic depressions
(4-8ys) in the Bay of Bengal. The head of the funnel-shaped Bay of Bengal poses
perhaps the most serious threat from surges driven by the storm waves reaching
5-8 m high.
Nearly 85% of
the Indian mangroves are confined to West Bengal and the islands of the Bay of
Bengal. Mangroves are examples of open ecosystems with respect to both energy
and matter. These ecosystems are sensitive to external influences and have experiencing
severe degradation particularly in the deltaic region where the population density
exceeds 1,000 inhabitants/sq.km. The mangroves have always been useful to the
coastal people. The fishermen have been extracting form them firewood, planks
& posts, wood for the boat building, floats for the nets, thatch material protective
stains for the nets, and wood for making toys. Organic compounds such as, EPA,
pentacyclic triterpenoids, and the EPA precursor oleanolic acid are obtained form
mangroves. Decaying mangrove leaves have great medicinal value.
About
0.405 m ha have been reclaimed in West Bengal, and prawn and fish culture is practiced
in 30,000 ha giving an average yield of 500 kg/ha. Among 120 species of fish,
nearly 26 commercial species of fish and shellfish account for an annual yield
of 22,225 t from the estuarine waters and about 20,000 t / yr of marine fishes
form the inshore waters. Of the 2.45 million population of the coastal West Bengal,
about 80% are engaged in agriculture and the rest in fisheries, collection of
firewood, and honey.
The Hooghly
system receives domestic, agricultural and industrial wastes containing cellulose,
acids, alkalis, nitrogenous compounds, heavy metals, fly ash, phenol, sulphides
and pesticide residues which adversely affect the fish and fish food organisms
near the outfall regions. Matlah and other eastward estuaries receive Calcutta
and suburban sewage with organic load, heavy metals, ammonia, and synthetic detergents
flowing down through the Kulti and Bidyadhari estuaries. With the location of
the oil reserves, the environment may be threatened by hydrocarbons and other
pollutants also in the near future. Estuaries are dying for want of headwater
flow and siltation, resulting in the formation of land masses and change in the
water flow leading to soil erosion and landslides. Due to poor drainage facilities
of the embanked islands, wetlands are common and are used for brackish water farming.
The Midnapore coast provides favorable port facilities because of stable soil
and approach roads. However, in the Sundarbans, unstable banks, intervening wetlands,
silting of beds and changing topography do not permit permanent harboring facilities.
In the coastal West Bengal,
the problem of freshwater is fairly acute because of extensive abstraction from
a depth of 700-1,000 mtr. The shallow salt water table often renders stored water
in ditches and ponds brackish and the surface soil saline. The wind velocity (7-12
km hr) offers scope for its utilization for energy generation. Tourism facilities
in the Sunderbans are to be developed in view of an influx of 23,000 visitors
annually. The Sunderbans and the beaches of Digha and Baikali are considered as
fragile coastal areas through this study.
