Vaithilingam Selvam, R. Ramasubramanian, Kandasamy Kathiresan, M.G. Manoj Prasanna, K. A. Sunanda Kodikara, Mala Amarasinghe, Ena Suarez

Mangroves of South India and Sri Lanka, and Maldives is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology). It includes the marine ecoregions of Western India, South India and Sri Lanka, and Maldives. The mapped extent in 2020 was 249.2 km2, representing 0.2% of the global mangrove area. The environmental settings of this ecoregion differ widely ranging from open coast, lagoonal, deltaic and estuarine mangrove formations. The mangroves of Maldives grow on a calcareous mud substratum; those in all other parts of this ecoregion occur on fine terrigenous sediments. The biota is characterized by 21 species of true mangroves. The mangroves of the southernmost east coast of India are dominated by a single, highly saline-tolerant species: Avicennia marina. In contrast, elsewhere in this ecoregion, diverse species constitute the mangrove floral community. There are at least five endangered mangrove-associated bird species and one shark species in the IUCN Red List. The major threats to the mangroves of this ecoregion are reduction in freshwater flow and subsequent development of hypersaline conditions; conversion of mangroves for aquafarming and tourism development; changes in sediment dynamics; poor exchange of tidal water; and climate change especially sea-level rise and storm surges. Today the South India, Sri Lanka, and Maldives mangroves cover ranges between 197.1 and 249.2 km2 according to different available sources. This is higher than our broad estimation for 1970. The mangrove net area change fluctuates between -4.7 and -26.8% 1996 to 2020 based on the data sources. If this trend continues, an overall loss between 49% and 58 % is projected over the next 50 years. Under a high sea-level rise scenario (IPCC RCP8.5) 82.7% of this ecoregion’s mangroves would be submerged by 2060. Moreover, 3.2% of the mangroves are undergoing degradation, with the potential to increase to 9.5% within a 50-year period, based on a vegetation index decay analysis. Overall, the South India and Sri Lanka, and Maldives mangrove ecosystem is assessed as Critically Endangered (CR).