The Thanjavur Forest Division has been conserving sea grass in Palk Bay in order to save the endangered sea cow as well as mitigate climate change
Dugongs are marine mammals that relish sea grass, the most productive plant communities. Since dugongs (sea cow) and sea grass species (see box) are interdependent and interrelated, the extinction of dugongs is threatening sea grass meadows the world over. Interestingly, sea grass can sequester up to 11 per cent of the organic carbon buried in the ocean even though it occupies only 0.1 per cent of the total ocean floor. Conserving dugong, thus, improves not only sea grass but also helps mitigate global warming.
Sea grass grows in abundance in Palk Bay, which is a strait between Tamil Nadu and the Mannar, Northern Province, Sri Lanka and also a highly productive coastline in the southeast coast of India. The Tamil Nadu Forest Department has taken up a sea grass rehabilitation project which also targets the conservation of dugongs near Manora village, Thanjavur, Tamil Nadu in Palk Bay.
The Species Conservation Action Plan for Sea Cow was organised by the Thanjavur Forest Division in 2016 under the Tamil Nadu Biodiversity Conservation and Greening Project. The Japan International Cooperative Agency financially supported the project and various departments were involved in the training workshops, including marine police, fisheries, veterinary and police.
Sea grass and its eco-services
Sea Cow or dugong
Sea grass absorbs carbon from the atmosphere (up to 83 million metric tons of carbon annually) and also absorbs carbon from water to build their leaves and roots.
Found along the coasts of about 48 countries, dugong is a “Critically Endangered Species” as per the International Union for Conservation of Nature.
When parts of sea grass plants and associated organisms die and decay, they get buried in the sediment.
There are just 250 dugongs in India spread across Gulf of Mannar, Palk Bay, Gulf of Kutch and Andaman & Nicobar Islands.
One acre of sea grass can sequester 740 pounds of carbon per annum, the same amount emitted by a car travelling around 6,212 km.
Dugong is the only marine herbivorous mammal.
The complex architecture stabilises the bottom sediments, which reduce wave energy and current velocity. Since they reduce turbidity, coastal erosion is decreased.
Dugong seek shelter in sea grass and are inter-dependable.
Sea grass meadow in Palk Bay serve as a breeding and feeding ground for fish, molluscs, invertebrate species and mammals including, Dugong, sea horses, sea cucumbers and pipe fishes are other co-habitants.
Due to the threats faced by dugong from humans, crocodiles, large sharks and killer whales, their distribution range in certain parts of the world is now absent. Research has shown that where there is no human impact, dugong population increases only by about 5 per cent per annum. If more than about 2 per cent of adult female dugongs are killed every year, their population will decline drastically. Dugongs are harvested for food, meat, oil, medicaments etc. When females are hunted, it leads to reduction in the breeding stock.
Activities such as pollution, trawling and silt accumulation by mining, mismanagement of catchment or coastal development has an adverse impact on the population of dugongs. Loss of sea grass due to large scale floods can destroy their feeding and breeding grounds. The noise by vehicles such as boats may scare the animals and fishing lines and nets can prove fatal.
The endangered species can be saved
Current and long-term monitoring of dugongs shows that their populations can be maintained or recovered by ensuring protection of their habitats, reducing their deaths due to fishing. Research and monitoring scientists are tracking dugongs through the aerial survey method to determine the grazing areas, duration and depths of dives, movements between grazing areas and between regions. By identifying the main feeding areas through aerial tracking, the management of net fishing and boat traffic in these areas are regulated. Population management can be done by creating awareness among the fishing community.
Fishermen take charge
Awareness programmes have been organised in many coastal villages, such as Kazhumanguda, Karanguda, Mallipattinam, Chinnamanai, Manora, Velivayal, Pillayarthidal, Somanathanpattinam, Sethubhavachathiram, along the coast of Thanjavur. Street plays with dance, music and drama explained the value of sea grass for sustainable fishing and conservation of dugongs. Hoardings, booklets and brochures were distributed among the fishing villages, schools, colleges and other line departments.
Fishermen were motivated to release dugongs into the sea by giving awards. Since releasing dugongs means the expensive nets have to be cut open, they were given compensation by the forest department. The awareness campaigns proved meaningful as the authorities released dugongs caught accidentally by fishermen, twice. On December, 2016, the fishermen from Keezhathottam village who caught two dugongs accidentally informed the Forest Range Officer (FRO), Pattukottai. The dugongs were released into the sea at Manamelkudi near Kattumavadi. One more dugong was also released at Kodimunai on January 30, 2017 and the fishing villagers who released the dugongs were duly compensated by the forest department. Besides, the persons who gave information about the movements of dugong were also rewarded.
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