| The earthquake and tsunami of December 2004 caused huge changes in the coastal systems of Andaman and Nicobar Island |
AN 11-PICTURE COMPILATION showing the huge uplift and destruction of coral reef - covered with mud and debris - west of Interview Island.
December 26, 2004 will be etched forever on our memories for the tsunami that killed lakhs of people and caused unprecedented damage in the coastal regions of South Asia and South East Asia.
PADDY FIELDS AND mangrove forests lie submerged at Sippighat, on the outskirts of Port Blair. The old channels of the creek are still visible, clearly outlined by dead mangrove trees.
Among the worst hit areas in India were the fragile Andaman and Nicobar Islands, particularly the southern group of the Nicobars. Of the nearly 3,500 people reported dead and missing in the entire islands, nearly 3,000 were in the Nicobar group, which has only about 10 per cent of the Andaman and Nicobar Islands' estimated population of 400,000.
Another important indicator of the damage is the area of agricultural and horticultural land that suffered temporary or permanent submergence. In the Nicobars nearly 6,000 hectares (14,826 acres) has been damaged, and in the Andamans about 1,800 ha (4,447.8 acres). The magnitude of the damage to the Nicobars becomes clear when one considers the fact that the Andaman group, with a total area of about 6,400 sq. km, is more than three times the size of the Nicobar group. In the Andamans, too, much of the damage occurred in the southern parts, in the Little Andaman and South Andaman islands. The northern groups escaped virtually unscathed.
The explanation of this stark contrast lies in the earthquake that set off the tsunami. The tectonic activity initiated in December 2004 caused a significant shift in the lay of the islands. Assessments done by Dr. Roger Bilham of the University of Colorado indicate that the northern parts of the Andaman group of islands experienced a permanent average uplift of four to six feet (1.2 metres to 1.8 metres) while most parts of the Nicobars went significantly under - four feet in Car Nicobar and a staggering 15 feet (4.57 m) at the southernmost tip - Indira Point on Great Nicobar Island. The pivot of this swing experienced by the islands can be calculated to be roughly located south of Port Blair.
AT JOGINDERNAGAR, GREAT Nicobar Island, buildings and coconut plantations that were far inland before the tsunami are now right on the coastline, on the new beaches.
In the Nicobars, therefore, the water that the tsunami brought in stayed back, permanently inundating huge areas of coastal and low-lying forest and, where they existed, fields, horticultural plantations and settlements of the Nicobaris and the settler families. Among the most significant but little studied or understood implications of this sudden, phenomenal change in the architecture of the islands is the impact on coastal and marine ecosystems such as mangroves, coastal (littoral) forests and coral reefs.
The submergence of the coast has brought this well, filled with sand as a result of wave action, right to the edge of the coast.
Proof of the damage caused to mangroves and littoral forests lies everywhere in the Nicobars. A continuous wall of submerged, dead, brown, decaying timber of various kinds engulfs every single island. The extensive damage to these forests has also had catastrophic implications for a diverse range of rare and endemic flora and fauna that inhabited these systems.
For instance, the submergence in the Nicobars has permanently destroyed a huge part of the nesting habitat of the Nicobari Megapode, an endemic bird that scrapes together a mound of earth for its unique nest. A survey carried out by Ravi Sankaran of the Coimbatore-based Salim Ali Centre for Ornithology and Natural History (SACON) in the first few months of the disaster reported that nearly 1,100 nesting mounds were lost in the immediate aftermath of the earthquake and the tsunami.
A survey in early 2006 by K. Sivakumar, who was a student of Ravi Sankaran and is now with the Wildlife Institute of India in Dehradun, covered nearly 110 km of the coastline in 15 islands in the Nicobar group. The Nicobari Megapode was the subject of his doctoral thesis and he had conducted extensive surveys of the bird in 1993-94. Sivakumar's present estimates indicate that there are now only about 500 active nesting mounds of the bird and that its population is less than 30 per cent of what was reported a decade ago. While the bird has been hit badly, fears of its extinction have been put to rest.
Little, unfortunately, is known of the other littoral forest-dwelling fauna, mainly the Giant Robber Crab, the Reticulated Python and the Malayan Box Turtle. South Sentinel, a 1.6 sq. km flat, uninhabited island that is also a wildlife sanctuary, had one of the most significant populations of the Giant Robber Crab. Beaching a boat here was always a tricky affair and after the changes in December 2004 it is reported to have become even more so. No credible scientific information exists of the present situation on this island, and therefore of the Robber Crab.
UPLIFTED BED OF mangrove creek.
CORAL REEFS UNDER DEBRIS
Another ecological system that has been affected on either side of the pivot is the pristine and extensive coral reefs that the islands are famous for. In the Nicobars the damage was caused by submergence, increased turbidity of the water and the sheer physical impact of debris.
Surveys by the Zoological Survey of India (ZSI) have reported significant impact on the coral reefs around the Central Nicobar group of islands, including Camorta, Nancowry, Trinket and Katchal. R Jeybaskaran of the ZSI's regional station in Port Blair had conducted extensive surveys in the waters of Great Nicobar in 1999. He took a re-look at the reefs after the tsunami only to find that large coral areas were under debris, sand and mud. Also reported was a noticeable reduction in associated coral fauna such as nudibranchs, flat worms, alpheid shrimps and hermit crabs.
Another interesting associated change has been the sudden increase in the otherwise uncommon `Milk Fish' Chanos chanos in the Great Nicobar waters. Fisherfolk catch them in such large numbers that they are now called tsunami macchi.
THE GIANT ROBBER Crab in South Sentinel Island is said to be one of the most badly affected species of fauna by the destruction of coastal forests.
While the Nicobar coral reefs suffered on account of submergence, those in the Andaman waters were permanently thrust above the high-tide line, destroying them in weeks. Among the first to survey these areas for the changes was Harry Andrews of the Andaman and Nicobar Environment Team. His report and that of Ravi Sankaran of the Nicobars were published as part of a series by the Wildlife Trust of India - `Ground Beneath the Waves - Post Tsunami Impact Assessment of Wildlife and their Habitats in India'.
Andrews has estimated that more than 50 sq km of pristine coral reefs were thoroughly exposed and destroyed, and the largest single area, on the west and north of Interview Island measured 25 sq km. Like the coral reefs, these parts of the Andamans have also seen loss of mangroves because of the fact that unlike the Nicobars they are now permanently above the high water mark.
The survival of the Nicobari Megapode with its nesting mound (partly seen) in low-lying coastal forests is now under threat.
Significantly, most of the experts and others working on ecological issues in the islands have unanimously advocated no intervention as the best form of intervention. "Allowing nature to take its course is the best way," says Ravi Sankaran, "to allow habitats to restore themselves, and species to colonise areas. Leaving areas alone should be the preferred management option."
Natural systems are bound to respond in complex ways in an attempt to move towards some kind of equilibrium and this should be allowed to happen. The example of sea turtles is a good one. The beaches of the islands (particularly in the Nicobars) that have been important nesting sites for four species - the Giant Leatherback, the Green Sea Turtle, the Olive Ridley and the Hawksbill - were all lost when the coastline in the southern group submerged.
In a few months, however, new beaches started to appear, like soothing, soft caresses all along the altered alignments of the ravaged islands. The turtles, too, were back and there are now regular reports of their using these new beaches for nesting.
SUBMERGED AND DEAD coconut plantation in Great Nicobar Island.
In the Andamans, too, many of these exposed reef areas rapidly filled up with sand, creating additional new landmasses and new beaches. The process goes on and change continues to happen. What will be the nature of the equilibrium ultimately attained? For the answer we have to wait and watch.
Pankaj Sekhsaria is National Foundation for India Media Fellow 2005-06 for writing on the Andaman & Nicobar Islands.
Highly informative, useful and alarming. The question is who can equal nature's wrath.
ReplyDeleteNanda
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