Distribution of Avicennia spp. in the Andaman and Nicobar Islands with special reference to new distributional reports and post-tsunami colonization patterns

Post 2004 tsunami and earthquake, the landmass of Andaman and Nicobar Islands (ANI's) experienced uplift (North Andaman and Mayabunder) and subsidence (South Andaman & Nicobar Islands). The altered geomorphology modified the tidal regime, which resulted in mangrove degradation in their current locations and the formation of new intertidal zones potential for mangrove colonization. Avicennia species; a pioneer in mangrove succession was expected to colonize such new intertidal zones. Therefore, to understand the colonization pattern of Avicennia species in these new intertidal zones and their distribution in the old forests, we surveyed 79 sites across ANI's (55 Andaman and 24 Nicobar Islands). Our survey confirms the presence of three Avicennia species namely A. marina, A. officinalis, and A. alba – a new distribution record to the ANI's. Further, A. marina was found to be the most widely distributed, and abundant among three Avicennia species (Relative Abundance (RA) – 97.92%; Relative Frequency (RF) – 68.75%). In contrast, A. officinalis (RA – 1.93%; RF – 26.25%) and A. alba (RA – 0.16%; RF – 5%) were found limited in their distribution and abundance. As per the IUCN Red List, the Avicennia population is decreasing globally, whereas, its population may increase significantly across ANI's due to the availability of vast new intertidal zones. Hence, Avicennia spp. can be utilized in the plantation programs to facilitate rapid colonization in the unvegetated potential mangrove habitats across ANI's. Such an effort will improve the mangrove ecosystem services that were hampered due to mangrove degradation by the 2004 tsunami.