Bhitarkanika Mangroves: Aiming for desert

The rich mangroves of Bhitarkanika National Park of Orissa are in jeopardy if the governments proposed water diversion for industrialisation takes place soon. Without the mangroves, the Gahirmatha Marine Sanctuary would turn into a “marine desert”. For the needs of proposed massive steel industry in the adjacent Jajpur district, the government has promised to divert water from the Brahmani River to steel manufacturers. Fresh water of the river mixes with the sea water to produce brackish water ideal for mangroves which are sensitive to change in salinity. The reduction in water flow would lead to drastic changes in the water regime of Bhitarkanika Mangroves.

The rich mangroves spread over 195 sq km have a high level of bio-diversity as 62 of the world’s 73 mangrove species are found in the Bhitarkanika mangroves. It was also the habitat for over 1350 salt water crocodiles and served as breeding ground for fish, crabs and shrimps. Nutrients from this area are flushed out to the Gahirmatha Marine Sanctuary which attracted the world’s largest population of Olive Ridley sea turtles for mass nesting.

The lack of normal flow of fresh water would increase saline ingression upstream which would affect the local flora and fauna as well as the livelihoods of farmers and fishermen dependent upon the Brahmani and Kharashrota rivers. This could also trigger a man-wildlife conflict as the estuarine crocodiles might leave the core sanctuary area and migrate upstream once the salinity increased in the water.

Status of Mangroves in Orissa

The mangroves all along the Orissa coast are threatened due to high density of population in these areas and competing demand for land for agriculture and prawn farming. The mangrove belt in Kendrapada district called the Bhitarkanika mangrove forests, comprising areas between in the Dhamara mouth to Barunei on the coast, has been notified as Bhitarkanika Sanctuary (672 Sq.km.). Part of this area (145 Sq.km) is notifies National Park. This stretch of mangrove is the only area, which is relatively well preserved. Mangrove vegetation in Mahanadi delta region between Barunei mouth to Mahanadi mouth (Paradip) is fragmented and degraded due to large-scale encroachment of these areas. Further south, sparse mangrove vegetation occurs along the coast from Mahanadi mouth to Devi mouth. Degraded mangroves also occur to the north of Dhamara mouth up to Chudamani in Bhadrakh District coast, and also on Subarnarekha mouth in Balasore District.

Ecosystem Value

Mangrove wetland encompasses a host of ecosystems namely; estuarine / brackish water ecosystem, riverine ecosystem, forest ecosystem, etc. Each such ecosystem supports food chains within it to maintain the balance of nature.

Mangroves have been considered as “land builders”. It is believed that the roots of mangroves secrete a substance, which modifies the coarse particles into fine ones and help in soil formation. The tangles of stilt roots also help in sedimentation of particulate matter. Network of mangrove roots provide firm anchorage to the banks of tidal rivers, creeks and also the coast line. It effectively arrests river bank and coastal erosion and ultimately helps in controlling flood damages. It also exercises a moderating influence on the cyclonic wind and storm surges. In the past, serve cyclones and tidal surges of the coastal Kendrapara district; particularly the Rajnagar area, is known to have been effectively controlled due to the presence of thick mangrove vegetation in the zone of Bhitarkanika and the adjoining Mahanadi deltaic area.

Mangroves are salt tolerant plant species found in the inter-tidal regions along the creeks and estuaries near the coast, on the river mouth. They play a very significant role in protecting the hinterland against (i) cyclones and (ii) the ingress of sea water during tidal surge. Mangroves stabilize coastal land mass against sea erosion. They are repositories of immense biological diversity and are also the nursery and breeding ground of several marine life forms, such as species of prawns, crabs, fishes and molluscs. Mangroves sustain the ecological security of the coastal areas as well as livelihood security of the thousand of fisherman and other who leave in these areas.

Ecosystem Functions

Mangrove areas support a range of interconnected food webs, which directly sustain the fisheries. Algae and detritus sustain shrimps and prawns, which provide a food source for species such as Bhekti (Lates sp.) Cat fishes etc. Fish and prawns spend most of their adult life at sea and return to the mangrove areas and vice versa to spawn. Some of the commercially important fishes are Ilisha, (Hilisa illisha), Khainga (Mullet sp.), Bhekti (Lates calcarifer), Kantia (Mustus gulia), Kokill (Anchovella sp.) etc. Prawns such as Penaeus indicus, tiger prawn (Penaeus monodon), Metapenaeus affinis and crabs, mainly the mud crabs (Scylla serrata) are exploited in large numbers by the fishermen both in the breeding and non-breeding seasons. Mud skippers, a typical fish reside around and in mangroves. These fishes are able to survive short periods of aerial exposure, skip around on the water and mud and build chimney like burrows.

Ecological Vulnerability

Ecological Vulnerability is due to large-scale encroachments, current living styles and dependence of people on Bhitarkanika. Although there are known pollution causing Industries like Oswal and PPL, etc. around Bhitarkanika which could affect the ecological soundness, use of chemicals and pesticides in agricultural fields and effluents coming from large number of prawn gherries has some impact on the wildlife depending on the aquatic habitat.

THREATS

Encroachment of forestland:

Encroachment of forestland by the migratory people and conversion of the same into common homestead and agriculture land are the main problem in this locality. This has put tremendous biotic pressure on the potential mangrove forests. In the encroached land, the tidal creeks are being blocked by earthen bunds, which prevents the natural tidal flow and gradually the mangrove vegetation perish from that area.

Aquaculture:

In and around the site, a large chunk of the agriculture land adjacent to rivers and creeks have been converted to prawn farms. Even number of people from outside the area have purchased private land along the coast as well as along the creeks and converted the same to aquaculture farms. They are discharging the untreated effluents from the farm to nearby rivers and creeks and thereby affecting the aquatic fauna and the mangroves.

Fishing:

Fishing in the rivers and creeks by the surrounding local people is posing several adverse factors, the major being obstruction of migratory routs of fishes and blocking of free movement of crocodiles. Sometime, fishing by the local people leads to virtual closure of creeks, thereby the tidal inundation is hampered to a considerable extent. Fishing in the near shore and off shore coastal waters resulting in mortality of endangered Sea turtles, Dolphins, etc. Movement of fishing vessels in the congregated breeding ground of Sea turtles is affecting the social facilitation in Ridleys and disturbing the mating pairs.

Live Stock and Grazing:

An estimated 70,000 cattle depend on the forest and meadow located therein for grazing during cropping season. This put pressures on mangrove vegetation especially Avicennia species.