Drivers of mangrove colonization in the uplifted coral reefs and sea beds in the North Andaman Islands, India

Coastal uplift by 1.35 m following the 2004 tsunami and earthquake in North Andaman has transformed coastal ecosystem, leading to extensive mangrove mortality and exposing supratidal zones currently occupied by dead corals and reef beds. These uplift zones located across at seaward edge are now acting as new intertidal zones where heterogeneous mangrove colonization is unfolding. To investigate the drivers of mangrove colonization, 299 plots of 10 × 10 m were established across 18 uplift sites (9 sites on each coast) in North Andaman during January–April 2023, where mangrove vegetation and associated explanatory drivers were recorded. Generalized linear models (GLMs) were used to identify factors influencing early-stage mangrove community structure. Mangrove species richness and abundance in the tree layer were primarily driven by the average canopy height, water pH, substratum type, and land uplift gradient. Meanwhile, the sapling layer richness and abundance were additionally influenced by the abundance and richness of the established tree community. Herbivory and marine debris also contributed to variation in colonisation pattern. Colonisation appears to increase with canopy height and generally decline with increasing water pH, while distance from remnant mangrove stands, and water salinity exhibited comparatively weak effects. These findings demonstrate that mangrove colonisation at the uplift sites are largely shaped by the complex interplay of environmental, physical, ecological, and anthropogenic factors, with canopy structure, substratum, and water chemistry acting as key correlates of early establishment. The study underscores the need for site-specific rehabilitation or plantation approaches that account for local structural, edaphic, and anthropogenic contexts to enhance mangrove colonization and long-term resilience in tectonically altered coastal systems.