Impact of extreme events on salt-tolerant forest species of Andaman and Nicobar Islands (India)

Abstract

Mangroves are the salt-tolerant plants that grow mainly in the tropical and sub-tropical intertidal regions of the world. Nature has therefore endowed mangroves with a series of remarkable adaptations which enable them to flourish in an environment characterized by high temperatures, wide fluctuating salinities and shifting of anaerobic substrates. The root systems show remarkable morphological, anatomical as well as physiological adaptations to withstand salinity and so do the leaves. Many mangroves exhibit vivipary-a specialized way of reproduction for propagation in unfavourable conditions. The mangroves are vulnerable to the consequences of climate change particularly due to sea-level rise. They are also considered to be an important carbon sink. It is estimated that the present annual loss of mangroves results into a loss of about 225,000 t of carbon sequestration potential per year with an additional release of approximately 11 million t of carbon from disturbed mangrove soils each year. In this chapter, a case study has been presented on the impact of an extreme natural calamity, i.e. tsunami, which happened on December 26, 2004 preceded by a massive earthquake of 9.1 on Richter scale on the mangrove vegetation in the Andaman and Nicobar Islands of India. The immediate damage to the mangroves was mainly due to the impact of tsunami. However, the massive earthquake that preceded the tsunami brought about changes in the geo-morphology of these islands resulting in significant rise of land in the northern islands and submergence of land in the southern islands of the Nicobar group. The results of the study are based on the analysis of temporal satellite data as well as field verification. The results show that there is a continuous degradation in the mangroves in North Andaman as well as Nicobar islands and the trend is likely to continue.