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Climate change impact on biodiversity of the Sundarbans

Dr. Md. Sohrab Uddin Sarker
We need survey and monitoring of the coastal areas particularly the Sundarbans to ascertain by the GIS (Geographical Information System) the probable sites of inundation due to sea level rise.Elevated areas may be developed above the expected sea water level to provide food and shelter and other environmental requirements to animals living in the sea level rise prone areas.
CLIMATE change resulting in sea level rise would cause severe environmental impact on the living resources including people and biodiversity in the affected areas. There are so many coast line associated islets and islands in the Bay of Bengal in the southern part of Bangladesh, e.g. Shandip of Chittagong, Shahpari and St. Martin of Teknaf, K u t u b d i a , Moheshkhali and Sonadia of Cox's Bazar and islets like Nijhumdip , Char Kukrimukri, Char Dale, Char Fashon, etc of Patuakhali, Barguna and Bhola districts. Lakhs of poor and homeless people live in these areas. Sea level rising 0.5-Im there will be catastrophic for these affected areas and people. They might need immediate shifting to nearby high lands.
Sundarbans, the biggest mangrove forest in the world consisting 6200km2 of forest and riverine areas lies there. It has been listed as World Heritage Site and is the most important ecosystem and protective natural barrier against the calamities like tidal surge, cyclone etc. This gift of nature would simply be submerged by the rising sea.
Impact assessment Biodiversity: There are 375 species of birds, 55 species of mammals and 83 species of reptiles and amphibians in the Sundarbans. Besides, more than 150 species of fish, 50 species of shrimp and other invertebrates also live there. It is the largest habitat of the most endangered Royal Bengal tiger, salt water crocodile, the leatherback sea turtle, python, king cobra and spotted deer. Besides, wild boar, rhesus monkey, dolphins, snake bird/darter, stork and ibis, sea eagle, vulture, finfeet, skua, forest eagle owl, swamp partridge, bustard quail, trogon, pigmy woodpecker, brown wing kingfisher, racket tailed drongo, ground thrush, forest wagtail, streaked spider hunter, nuthatch, scarlet minivet, ring lizard, sea snakes, green frog and other threatened species live in the Sundarbans.
Flora: There are shon grasslands at a number of places like Hiron Point, Kochkhal, Jamtoli of Katka, Rash Mela of Alorkol in Dublar and Kaiar chars. Besides, mangrove vegetation of the Sundarbans would be seriously affected by sea level rise. The pnematophores (roots of mangrove plants) regularly go under water twice daily during high tide for 1-3 hours. In the inter-tidal period trees in mangrove and coastal mud flat areas use to respire by specially growing roots called pneumatophores. Each tree has thou-sands of such pnumatophores growing up about 10 cm to Im high in the air and spreading 2-5m
around the base. These air roots are smaller in golpata, hantal, goran, etc. and longer in sundri, gewa. amur, keora, etc. If the sea level rises from 0.5 to Im the pneumatophores will remain under water permanently and trees will die due to problem of respiration and sand deposition.
Fauna--
Mammal: All herbivore animals will face shortage of food. Deer, hare, porcupine, arboreal monkey, rat and mice, etc. are purely herbivo-rous, seedivorous and fruigivorous. They have no other alternative but to die due to lack of selective food items e.g. grasses, leaves, seed, fruit, roots, etc. They do not move to highland areas either.
Deer will be the worst sufferer due to food shortage and habitat loss. During high tide deer usually move to high lands in the forests. Otherwise, remain standing in the water until the tidal water is receded. There will be no dry land left in the forest after sea level rise.
Wild boars can tolerate water more than deer and they swim but without food their fate will be the same as deer. Monkey is semi arbo-
real and may continue to survive longer than deer and boar. But when trees will start dyingdue to Inundation their fate will also be the same due to lack of food and shelter.
Carnivores like tigers, fishing cats, cevets, otters, etc. will face the similar problem: loss of habitat due to inundation and shortage of food due to lack of herbivores in the forest.
Tigers are the world's most endangered species and survive only in a few places including the Sundarbans of Bangladesh in very small number. Tiger is a good swimmer and may move from one place to another but the prevailing condition will not be favour-able. Tigers of the Sundarbans usually move to higher places during high tide, but whither that when sea level rises?
Birds: Resident and migratory terrestrial birds of the Sundarbans and coastal areas will create excess pressure and ecological problems on the existing fauna and flora where they will fly. Aquatic birds like herons, gulls, terns, owls, nightgers, wagtails, pratincles snipes, sandpipers, finfoot, culew, whimbrels, spoonbils, wild ducks will also loss their habitats along the coastal belt. Hole nesting birds like woodpeckers, kingfishers, swallows have better chance to survive for more time. They use to feed on the insects from wood and fish from water and flying insects from air, respectively, and all will breed in the tree holes. But changed climate will also affect their food chain.
Land birds like pheasants, red jungle fowl, quail, swamp partridge,tunki, rails, larks, field pipits, pittas, ground thrushes, babblers leave the forest because of lack of feeding, resting and breeding provision due to inundation of grass land, forest clearing etc.
Reptiles: Particularly the salt water crocodiles and five species of marine turtles, e.g. olive ridely, green hawksbiil and loggerhead are endangered species.
Crocodiles become more dominant because of expansion of habitat in the forests for preying on fishes and animals as food. But in absence of these food species how will crocodile survive?
Leatherback is the largest sea turtle of the world and are critically endangered. The leatherback turtles including other sea turtles lay eggs on the sandy beeches along the coastal zone mainly St. Martin's Island, Sonadia, Kutubdia, Moheshkhali, Cox's Bazar, Inani, Shapari dip of Teknaf and the Sundarbans every year from September-October to March-April. Thousands of sea turtles come to shallow water areas of the Bay where the males mate with females and the females lay eggs on the beaches nearby. They will certainly lose their breeding ground due to inundation by sea level rise. There will be no exiting beech for egg laying along the coast.
I^rge number of red crabs and other marine crabs and terrestrial insects will disappear from the coastal areas and the Sundarbans due to loss of habitat and food.
Recommendation We need survey and monitoring of the coastal areas particularly the Sundarbans to ascertain by the GIS (Geo-graphical Information System) the probable sites of inundation due to sea level rise.
Elevated areas may be developed above the expected sea water level to provide food and shelter and other environmental requirements to animals living in the sea level rise prone areas particularly in the Sundarbans.
A national commit-tee/task force should be formed immediately with relevant national specialists, experts, researchers, who will prepare plan and programme of works on priority basis.
Government, NGOs, international organisations should come forward to provide support to conduct the ecosystem assessment survey to prepare plan and programmes for the subsequent situation.
World Heritage Site and other international conservation organisations could come forward with supports for conservation of tigers, their prey species, habitats, other animals, as well as the environment on a permanentbasis.
Dr. Md Sohrab Uddin Sarker is Professor (Supernumerary), Department of Zoology, University of Dhaka.