Essay on tsunami impact on andaman and nicobar island
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Superseding initial reports that documented 60 to 70 percent mangrove cover loss, a new study reveals that in fact 97 percent of mangrove cover in the Nicobar Islands was razed due to the 2004 Indian Ocean tsunami.
The mammoth natural disturbance triggered the emergence of potential habitats for restoring mangroves and uncovered hitherto unrecorded mangrove species in the Nicobar Islands.
The study recommends measures to step up science-based mangrove restoration in a post-disaster scenario.
The 2004 Sumatra-Andaman earthquake followed by the catastrophic tsunami gobbled up landmass and stripped the coast of trees in the Nicobar Islands in the Indian Ocean. Mangroves, which flourish where land and water meet, bore the brunt of the natural disaster.
Superseding initial reports that documented 60 to 70 percent mangrove cover loss, a new study reveals that in fact 97 percent of mangrove cover was razed due to the event.
But the field study also points to a silver lining: the natural disturbance triggered the emergence of potential habitats for regrowing mangroves and uncovered hitherto unrecorded mangrove species in the Nicobar islands.
“A large number of trees were uprooted and most of the inter-tidal habitats were permanently submerged causing large scale tree mortality. However, the land drowning also created new inter-tidal habitats with potential for mangrove re-establishment at the erstwhile coastal terrestrial habitats and human settlements,” Nehru Prabakaran of Wildlife Institute of India, lead author of the study, told Mongabay-India.
The intertidal zone is the area between the highest-tide marks and lowest-tide marks. This habitat is covered with water at high tide and exposed to air at low tide.
A massive series of tsunamis set-off by the third largest earthquake recorded globally (the 2004 Sumatra Andaman earthquake) battered the immediate coastal areas of western Indonesia and spread out across the Indian Ocean to impact communities in Australia, Myanmar, India, Kenya, Malaysia, Maldives, Seychelles, Somalia, Sri Lanka, Tanzania and Thailand.
It severely damaged the coastal habitats of the Nicobar Islands – the landmass closest to the earthquake epicentre.
Almost no pre-tsunami mangroves left
The Nicobar Islands, a part of the Andaman and Nicobar Islands chain, stretch in an arc southward between Myanmar and the island of Sumatra in Indonesia.
At present, 21 islands (spread in three groups) form the Nicobar archipelago.
The Northern group consists of two islands (Car Nicobar and Batimalve); Central group consists of nine islands (Kamorta, Katchall, Nancowrie, Trinket, Teresa, Bombuka, Chowra, Tillanchong and Isle of Man); and the Southern group consists of ten islands including Great Nicobar and Little Nicobar.
During the tsunami, giant waves slammed into the coastline. The entire stretch of the Nicobar Islands was drowned into the sea to varying levels from 1.1 metres to 3 metres.
This sudden land drowning (due to tectonic subsidence) coupled with the tsunami altered the structure of mangrove forests, said Prabakaran of WII.
The severity of the subsidence can be gleaned from the complete submergence of Megapode Island – 0.2 square km in size and largely covered by mangroves at the time – located to the west of Great Nicobar island.
The 2009 Forest Survey of India report noted a decline in mangrove cover in the Andaman and Nicobar Islands by 20 square km attributing the loss to “after effects of tsunami.” The mangrove cover in 2007 (data for the period October-December 2006) is recorded at 615 square km while that for 2005 (data for the period October-December 2004) shows a cover of 635 square km. The 2017 report documented 617 square km of mangrove cover in the Andaman and Nicobar Islands.
“We found that mangrove cover in the Nicobar islands declined by around 97 percent, which is higher than the earlier reports. Except for one site in Car Nicobar island, there is no pre-tsunami mangrove vegetation surviving in Nicobar Islands in the aftermath of the tsunami,” Prabakaran said.
The study was carried out between 2010 and 2013 and was facilitated by Salim Ali Centre for Ornithology and Natural History (SACON).
Out of the 21 islands in Nicobar, 20 islands (except Batimalve island) were included in the study. The entire coastline of the islands was surveyed for the presence of mangroves and species diversity was elucidated.
The researchers documented 20 mangrove species from 34 sites across the Nicobar Islands, of which eight species were recorded for the first time from the island group.
“We think there could be two major reasons for the new reports of eight mangrove species. These islands are often under explored and therefore the species were already there but not reported,” Prabakaran said.