Structural complexity and tree species composition of mangrove forests of the Andaman Islands, India R. Kiruba-Sankar 1 & P. Krishnan 2 & S. Dam Roy 1 & J. Raymond Jani Angel 1 & M. P. Goutham-Bharathi 1 & K. Lohith Kumar 1 & P. Ragavan 1 & M. Kaliyamoorthy 1 & R. Muruganandam 2 & S. Rajakumari 2 & R. Purvaja 2 & R. Ramesh 2 Received: 25 August 2016 /Revised: 13 July 2017 /Accepted: 21 July 2017 /Published online: 28 December 2017 # Springer Science+Business Media B.V., part of Springer Nature 2017 Abstract This study reports the mapping, structural charac- teristics and distribution of mangrove species of the Andaman Islands. 79 mangrove patches were identified using Thiessen polygons of which, 53 accessible patches were surveyed dur- ing 2014–2015. Multiple linear transects were laid at each of the mangrove patches and data pertaining to diameter at breast height, basal area and height were recorded for all mangrove trees within a 10 × 10 m quadrat laid along the transects at 50 m intervals. Altogether, 178 quadrats were laid and 25 mangrove species representing 11 families and 14 genera were recorded. Of the 3073 mangrove plants enumerated in the present study, 96.06% were composed of trees (>4 m height), 1.99% of saplings (>1 m to ≤4 m height) and 1.95% of seed- lings (≤1 m height). The number of species per quadrat ranged from 1 to 9 and majority of the quadrats had 2–3 species. Density and basal area of mangrove trees ranged from 1252 ha -1 to 2200 ha -1 and 30.8 m 2 /ha to 59.6 m 2 /ha, respec- tively. High diversity indices (Shannon-Wiener index ranged from 1.65 to 2.24; Simpson index from 0.74 to 0.85 and Pielou’ s evenness index from 0.66 to 0.84) indicated greater diversity and even dispersion of mangroves in the Islands. The study also revealed that the mangrove forests of Andaman Islands were characterized by a mixed species composition. Most of the sites were represented by different combinations of dominant and co-dominant species, all from the family Rhizophoraceae. The present study highlights the need for conserving the mixed species mangrove forests of Andaman and Nicobar Islands and development of location-specific management plans for biodiversity conservation. Keywords Andaman Islands . Biodiversity . Conservation . Mangroves . Marine angiosperms Introduction Mangrove ecosystem has an important role in ecological and socio-economic terms (Ronnback et al. 2007; Walters et al. 2008; Malik et al. 2015). They offer various livelihood ser- vices such as coastal defense, fisheries, carbon storage, tour- ism, water purification, timber and fuel (Spalding et al. 2014). Further, they protect the integrity of the coast by acting as coastal buffers against cyclones, storms, tsunamis and other waves and tidal damages (Alongi 2008). Research on man- groves has increased exponentially in the last 50 years (Lee et al. 2014). Human interactions with mangroves have also been increased in recent days coupled with natural disasters, which make them more vulnerable to anthropogenic and nat- ural factors. As per recent estimate, mangroves have witnessed an annual loss between 0.16 and 0.39%, globally, due to rapid coastal development (Hamilton and Casey 2016) and mangrove cover has reportedly decreased in countries like China, Myanmar and Philippines, whereas, an increased man- grove cover was reported from India, Australia and New Zealand (Chaudhuri et al. 2015). Degradation and loss of these coastal buffering systems due to climate change and direct human impact negate the coastal protection they pro- vide during extreme events and increase their vulnerability (Ellison 2015). Therefore, it is necessary to manage the * R. Kiruba-Sankar rkirubasankar@gmail.com 1 Division of Fisheries Science, ICAR - Central Island Agricultural Research Institute, Port Blair, Andaman and Nicobar Islands 744 101, India 2 National Centre for Sustainable Coastal Management, Ministry of Environment, Forests and Climate Change, Anna University Campus, Guindy, Chennai 600 025, India J Coast Conserv (2018) 22:217–234 DOI 10.1007/s11852-017-0588-3