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Coastal Habitats (Living & Non-living Resources)

Living Resources

Digha-Sankarpur Coast

Flora
Coastal flora of special interest is found in the mini estuaries of Digha-Sankarpur area. The eastern extension of the Subarnarekha estuary has given rise to regeneration of Avicennia within the Talseri area adjacent to Digha. A similar mini-estuary at Jatra nala harbours mangal diversity like the highly valuable morphine rich medicinal mangrove Acanthus illicifolius thickets and Clerodendron inerme the back mangal. Further east the Digha Mohona was once a mangrove reserve now converted into a large aquaculture area. Even then the remnant mangrove species of Avicennia marina, A. alba, Excoecaria agallocha, Clerodendron inerme and Acanthus illicifolius are common. Salt marshes like Sweda maritime, Salicornia brachiata, Heliotropium currasivicum are met with. Another small estuary to the east is Jalda creek where salt marshes and sedges (Fimbristylis spp and Cyperus spp) dominate.

Fauna
Digha-Sankarpur area under Ramnagar Block-I in the western coastal stretch contributes a rich fishery from middle August to middle February of the year..  Among fin fish species there are:
Tenulosa ilisa, Pama pama, Setipinna spp., Trichiurus spp, Harpodon nehereus, Coilia spp., Ilisha elonhata, Sciaena biauritus, Polynemus indicus, Chirocentrus doral, Prawns – (Penaeus monodon, Acetes spp., Macrobrachium rosenbergii), Tachydurus jella, Stromateus cinereus, Polynemus peradiseus, Coilia sppp, etc.

The speciality of Digha-Sankarpur coast is the occurrence of two endangered species viz Lepidochelys olivacea the marine turtle and the Carcinoscorepius rotundicauda the valuable medicinal invertebrate the “Horse shoes”. Not much is known about their habitat and other details.

Sagar-Sundarban Coastal areas

General Characteristics
Sundarban with an area of about 10200 square kilometer of mangrove forest extends over two countries India (4,267 sq.km.) and Bangladesh (6,000 sq.km.). Out of this area of 4,267 sq. km., about 2,300 sq.km. is under forest canopy. An additional 5,400 sq.km. non-forest (reclaimed forest) human habited area along the north and northwestern fringe of mangrove forest within the Indian territory is also known as Sundarban. The Dampier-Hodges line has been accepted as the administrative landward boundary of Sundarban. The total area of Sundarban in India is therefore about 9600 sq.km. which forms the Sundarban Biosphere Reserve (SBR). SBR was notified under the administrative control of Department of Forests, Government of West Bengal in 1989 and was ultimately constituted as National Biosphere Reserve by UNESCO in 2001. The eastern part of the mangrove forest (about 2,585 sq.km.) has been declared as Sundarban Tiger Reserve (STR) area. A large part of the STR area (1,330 sq. km.) has been further declared as a National Park (known as Core area) by the Ministry of Environment and Forests, Government of India. Also three islands within the mangrove forests namely Sajnekhali, Lothian and Halliday have also been declared as Wildlife Sanctuaries by MOEF. Considering the overall ecological interest of forests of Sundarban, it has been declared as a World Heritage Site by IUCN.

Flora
The dominant flora of Sundarban is the mangrove. Altogether thirty true mangrove species, thirty mangrove associated plant species (back mangal) and thirty non-mangrove halophytic plant species have so far been identified from Sundarban. There are altogether fifty species of phytoplankton constituted by forty species of diatoms, eight species of dianoflagellates and one species of chlorophyceae and cyanophycaea. Sixteen types of zooplankton have so far recorded from Sundarban. About eighty species of algae adapted to salinity value from 15 to 35 ppt have been recorded from Sundarban. A succession of plant growth depending on the relative height of the land and consequent time of inundation by tidal water could be seen. In the lower intertidal mud flats, the halophytic grass is the pioneer species that rapidly colonises the newly silted up substrate. Floating seeds and seedlings of mangrove plants are arrested in this grass land and are anchored and germinate there. These seedling plants ultimately develop into dense mangrove forests of Avicennia, Sonneratia, Rhizophora, Ceriops and Bruguiera on these intertidal landforms. Ceriops, Phoenix, Xylocarpeus and Nypa grow on the upper intertidal levels to form ridge forests.

Fauna
The diversity and distribution of animals in Sundarban Biosphere Reserve can be appreciated from the following Table (ENVIS Newsletter).

Phyllum

Number of species occurring in:

Terrestrial Habitat

Aquatic Habitat

Total No of species

I    Kingdom Protista
                Subkingdom          Protozoa
                    Phyllum            Sarcomastigophora
                                          Apicomplexa
                                          Myxozoa
                                          Cilioohora 

 

26
19
--
2

 

19
5
6
29

 

45
24
6
31

     Total

47

59

106

II   Kingdom                          Animalia
                     Phyllum           Porifera
                                          Cnidaria
                                          Ctenophora
                                          Platyhelminthes
                                          Nemathelminthes
                                          Acanthocephala
                                          Nemartines
                                          Rotifera
                                          Mollusca
                                          Sipuncula
                                          Echiura
                                          Annelida
                                          Arthropoda
                                          Entoprocta
                                          Bryozoa
                                          Brachiopoda
                                          Chaetognatha
                                          Echinodermata
                                          Hemichordata
                                          Chordata
                     Class               Amphibia
                                          Reptilia
                                          Mammalia
                                          Aves
                                          Other classes

 

-
-
-
-
-
-
-
-
3
-
-
7
247
-
-
-
-
-
-
230
2
40
35
153
-

 

1
33
2
41
80
3
2
4
157
2
3
75
309
1
3
1
4
20
1
251
6
18
5
10
212

 

1
33
2
41
80
3
2
4
160
2
3
82
556
1
3
1
4
20
1
481
8
58
40
163
212

 

Total

487

993

1480

Grand Total                                  

534

1052

1586

 
Many rivers run across the Sundarban and falls into the Bay of Bengal. These rivers contain various fish species. Sundarban provides 90% of fish species of eastern coast and the coastal fishery of East India is dependent upon the Sundarban. There are over 300 species of marine and freshwater fishes, prawns and crabs occurring in this region.  Among fin fish species there are: Lates calcarifer, hilsha ilisha, Liza parsia, Liza tade, Harpadon nehereus, Plotosus canius, Pompus argenteus, Pangasius pangasius, Chanos chanos, Eleutheronema tetradactylum, Polynemous paradiseus and Pama pama. Shellfish species includes Penaeus monodon and Metapenaeus monoceros. There are two types of edible crabs: Scylla serrata and neptunus pelagiens. Among these, the most highly valued economic species is the Tiger prawn (Penaeus monodon).

The land is inhabited by Royal Bengal Tigers. Wildlife of Sunderbans also harbours jungle cats, fishing cats, Axis deer, wild boar, Rhesus monkeys, mongooses and the largest estuarine crocodiles in the world. Sunderbans is the breeding ground of immense variety of birds like Heron, Egret, Cormorant, Fishing Eagle, White Bellied Sea Eagle, Seagul, Tern, Kingfisher as well as migratory birds like Whimprel, Black-tailed Godwit, Little Stint, Eastern Knot, Curlew, Sandpiper, Golden Plover, Pintail, White-eyed Pochard and also Whistling teal. Wide variety of aquatic and reptile life forms are present that include Olive Ridley sea turtle, hardshelled Batgur Terrapin, Pythons, King cobra, Chequered killback, Monitor and lizards including the Salvator lizards. The Sundarban ecosystem is characterised by a very dynamic environment due to the effect of tide, flooding, salinity and cyclones. As a result several remarkable species are found such as estuarine crocodile (Crocodilus porosus), spotted deer (Axis axis), dolphins (Platanista gangetica, Orcaella brevirostris, Peponocephala electra, Neophocaena phocaenoides), marine turtles (Caretta caretta, Chelonia mydas, Eretmochelys imbricata, Lepidochelys olivacea and Dermochelys coriacea) and, the flagship species, the Royal Bengal Tiger (Panthera tigris).

The biodiversity is represented by the following taxonomic groups: over 40 mammal species, over 270 bird species, over 45 reptile species, at least 11 amphibian species, over 120 fish species, an unknown number of invertebrates, more than 330 plant species. The Sundarban tiger population is supposed to be the largest surviving tiger population in the world. Estimated number of tigers in the Sundarban is 274 as per 2006 census. The estimates for the deer in this area are 50-80,000, for wild boar 20,000, smooth Indian otter (Lutra perspicillata) 20,000 and rhesus monkey (Macaca mulatta) 40,000 to 70,000.

The colourful bird life along the waterways includes species such as kingfishers (9 species), raptors (38 species), herons, egrets, storks, sandpipers, whimbrel, curlew, gulls, terns, woodpeckers, barbets, shrikes, drongosa, mynahs, minivets, babblers and many others. Lucky birders may catch a glimpse of masket finfoot (Heliopais personata).
The Sundarban is surrounded by a very densely populated area, therefore human pressure is important. Around 1.2 million local users reside seasonally in the area for fishing and other resource use activities. Commercial hunting was a problem mainly before the 1970s and this resulted particularly in a serious depletion of the crocodile populations and to a lesser extent to the deer population. Although the protection has improved significantly in the last decades, illegal hunting is still occurring on an incidental basis and fishery is having an adverse impact on the populations of the remaining turtle and crocodile populations as these animals drown frequently in fishing nets.

Due to natural processes, fresh water discharge of the Ganges and Brahmaputra catchment is decreasing as main waterways are shifting eastwards (excepting Hugli estuary where fresh water of about 40000 cusec flows at least during the driest days through Farakka barrage). Further, the total annual discharge is decreasing due to intensifying land use (namely irrigation) upstream. The role of this change is not yet clear, but is evident that it will influence wildlife populations and vegetation in the long term.

However, the main threat today may come from outside the area in the form of pollution. Toxic products (pesticides, etc.) enter the system due to upstream pollution in the huge Ganges catchment. Pollution may be a direct source of mortality, but it may also reduce the health, increasing the mortality rate on the long term. Many products such as pesticides have also been proved to reduce the reproductivity (birth rate) in animal populations. A future threat is the exploitation of mineral gas, which is likely to be found abundant in the underground of the Sundarban.

Some species that have become extinct during the last century are: javan rhinoceros (Rhinoceros sondaicus), water buffalo (Bubalus bubalis), swamp deer (Cervus duvauceli), gaur (Bos gaurus), hog deer (Axis porcinus), marsh crocodile, (Crocodilus palustris).


Non-living Resources

Placer minerals

There is no placer mineral deposit on and off shore part of the coastal zone of West Bengal.

Minor Forest Produce of Sundarban

Tree farming programme on private land, village wood lots as well as roadside plantations and mangrove plantations raised on the mudflats of the numerous streams and rivers outside government forests help to meet the need of the local people for fuel wood and small timber, including building materials. The habitat shows evidence of excessive felling in the past. Timber smuggling is still a threat to this Tiger Reserve. Honey collection on permit basis is limited to the buffer area. Annually, about 38.2 MT of honey and 1.4 MT of wax are collected from the SBR (based on 2006-07 figure).

Ports and harbours

Haldia Port is located about 104 km south of Kolkata. The fourth largest port in India, Haldia dock system forms part of the Kolkata port complex. It is situated at the confluence of the Haldi and the Hugli rivers away from the open coast. The dock complex is located on the west bank of the river Hugli, 100 km from the pilotage station at Sandheads in the Bay of Bengal.  The port handles over 28 million tons of cargo every year. It has a modern dock system for handling large vessels. Other facilities include a full-fledged container handling facility and a jetty for handling bulk chemicals. Haldia maintains a nominal ship-waiting period and a low turn round time for vessels. The dock complex is connected through National Highway 41. The port has been on a forefront of privatisation. Two of its berths have been leased to leading enterprises and a large number of leading organisations are keenly interested in leasing facilities as well as leasing land for setting up port facilities. The Dock System has two riverine oil jetties and eight berths inside an impounded dock.

Ground Water

In the coastal area of West Bengal a clay blanket of 20 – 30m thickness is generally present below which brackish water aquifers occur within 120 m depth in the western part of Hugli river and within 150 – 180 m in the eastern part of it. A group of fresh water aquifers occur in coastal tract of East Medinipur within the depth span of 120-360 m sandwiched between saline/brackish water aquifers. In the extreme south-eastern part of the coastal belt brackish water aquifers occur within 360m depth. The fresh and brackish water aquifers are separated by a 15 – 20m thick impervious clay layer.

In the Digha-Ramnagar area of East Medinipur district, a shallow fresh water aquifer exists down to a depth of 12 m bgl in the sediments of present day dunes from which water may not percolate downward due to the presence of underlying thick plastic clay. An area of 150 sq km around Contai, Purba Medinipur district, aquifers contain brackish to saline water at various depths except those near surface and sand dune aquifers. Also in some localized pockets in South 24 Parganas district, sand horizons within a zone of 20 – 50m at the top having fresh water occur. The distribution of salt water – fresh water aquifers in the coastal tract is generally uniform with fresh ground water overlying saline ground water underneath.

The Haldia region is important from the point of view of ground water utilization in a rapidly growing coast based industrial hub of West Bengal. Drilling for ground water within the Haldia Industrial complex area reveals that sediments down to a depth of 115 b.g.l. are generally argillaceous in nature with few sand horizons with brackish to saline water. Below the depth of about 115 metres, the sediments are by and large arenaceous down to depths of little over 300 m. These sandy aquifers contain fresh ground water. Below the depth of 305 m, the unconsolidated sediments by and large comprise clayey material with sub-ordinate sand horizons. Assuming ground water draft of 400 MCM, a balance of about 80 MCM may now be available balance resources available in the Haldia region. 

In the Digha Sankarpur area, two freshwater and one brackish to saline water aquifer horizons have been identified:

  1. Basal sand dominated confined aquifer system, extending from 160 m to 300 m drilled depth with fresh water of very high quality. Salinity in this zone is from 0.6 to 0.9 gm/litre and iron content is generally high.
  2. Middle coarse sand dominated aquifer extending between 15 and 80 m, with occasional brackish contamination with salinity range of 4-6 gram/litre with impermeable clay layers separating the fresh water bearing zone
  3. Upper dune sand sequence forming unconfined fresh water aquifer extending up to 9 m with a salinity range of 0.7 to 1.1 gm/litre increasing downward. Although used extensively in the villages, hotels and holiday homes, the water quality is poor due to contamination of coliform bacteria and high concentration of chloride and iron and high hardness and alkalinity.

All the aquifers are recharged by monsoon rain but the piezometric surface of the deep aquifer is depressed by 9 metres during January to March due to heavy withdrawal for cultivation. Increasing demand and drawal of ground water from the deep aquifer, there is real threat of saline water ingression if excessive withdrawal is regulated.