Upheaval of the natural world
Pankaj Sekhsaria
First Published : 01 Feb 2011 12:31:00 AM ISTLast Updated : 01 Jan 2011 12:35:00 AM IST

One of the least explored or studied aspects of the tsunami and earthquake of December 26, 2004 is the drastic ecological and environmental change that was brought about in the Andaman and Nicobar Islands. Here, and this is little understood, too, it was the 9.1 magnitude earthquake and not the tsunami itself that caused the greater damage. The explanation lies in the tectonic activity which caused a significant and permanent shift in the lie of the islands. With a pivot roughly located near Port Blair, the islands saw a huge swing like that of a see-saw — the Andaman group of islands were thrust upwards by four to six feet, while parts of the Nicobar Islands went significantly under — four feet in Car Nicobar and nearly fifteen feet of submergence at the southern most tip — Indira Point on Great Nicobar Island.


Ecologically, both groups of islands were impacted dramatically, though in diametrically opposite ways.

The Nicobar Islands

Anecdotal accounts indicate that the submergence in the Nicobars happened even before the waves of the tsunami hit the islands. Not only did the waves hit hard, the water they brought also stayed back due to the submergence.

Hundreds of square kilometres of coastal lands including mangroves, littoral forests and horticultural plantations were instantly and permanently submerged.

The coral reefs were also hit due a combination of the submergence, the resultant increase in turbidity and the physical damage caused by the tons of debris thrown back and forth by the waves. The Zoological Survey of India reported large-scale sedimentation on coral reefs as also a significant reduction in the number of other associated coral reef fauna such as nudibranchs, flat worms, alpheid and mantis shrimps and hermit and brachyuran crabs. In an interesting development immediately after the tsunami, fishermen from Great Nicobar reported a sudden and huge increase in the catch of Milk fish, Chanos chanos. So huge and sustained was the harvest that the fish has come to be called the ‘tsunami macchi’ here.

Most of the beaches in the Nicobars, which were nesting sites for four marine turtle species — the Giant Leatherback, the Green Sea Turtle, the Olive Ridley and the Hawksbill — were also completely lost. This change however was a short-lived one and new beaches started to form along the altered alignment within months. Nesting turtles too were back again very soon.

Large tracts of mangroves and coastal forests were however, completely destroyed and for many months after the disaster the islands in the Nicobars could be seen encircled by an endless brown wall of dying and decaying trees. This raised considerable concern over the fate of some of the rarest species of fauna that inhabit these coastal habitats, in particular, the endemic Nicobari Megapode, a ground nesting bird that scrapes together a mound of earth as a nest in low-lying coastal forests.

Rapid assessment surveys by the Salim Ali Centre for Ornithology and Natural History (SACON) reported that the bird had lost 70 per cent of its population in the aftermath of the disaster. While the bird has certainly been hit badly, it was not as bad as was initially feared.

But little is known of the other equally vulnerable, slow moving, coastal forest fauna such as the Giant Robber Crab, the Reticulated Python and the Malayan Box Turtle.

The Andamans

Areas around Port Blair also experienced permanent submergence (about 2-3 feet) and saw a fate similar to the Nicobars. Mangrove marshes that had been converted to paddy fields over many years in Sippighat just outside Port Blair, were permanently submerged.

There was one dramatic, though short-lived change here as well. For the first few months immediately afterwards, this area became famous for the production of the best prawns that residents of Port Blair had ever eaten.

The northern part of the Andamans, however experienced the opposite situation. Huge areas of coral reefs were permanently thrust above the high tide line destroying them within weeks. A rapid field assessment carried out by Andaman and Nicobar Team estimated that more than 50 sq km of coral reefs had been exposed and killed, mainly to the west and north of Interview Island. These parts also saw the drying up of large mangrove areas, as these too were pushed permanently above the high tide line.

While there has been concern on the negative impact of all these dramatic changes, experts and ecologists have suggested that the best intervention would be no intervention at all. In the context of the geological time scale, it has been argued, such cataclysmic events may have created this island chain in the first place — it is a natural event and species and habitats will respond in due course.

Importantly, the entire coastline of the islands has been altered and there is an urgent need to re-calibrate it, particularly, for any implementation of coastal protection and regulation provisions and to ensure meaningful and environmentally sensitive development in the future. Significantly, the situation also offers an unprecedented opportunity to observe and understand long-term changes that take place in natural systems after such a dramatic event. Some have already been seen and others could take years, even decades to reveal themselves. Needless to say, these would be fascinating developments to watch out for.

Link - http://expressbuzz.com/magazine/uphe...ld/235827.html