Donald Macintosh, Ena Suarez, Toe Aung, Daniel A. Friess, Maeve Nightingale, Marcos Valderrabano

The 'Mangroves of the Andaman' is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology) within the Andaman province. It includes intertidal forests and shrublands of the marine ecoregions of the Andaman and Nicobar Islands; the Andaman Sea Coral Coast of Myanmar and Thailand; and northwest Sumatra. The diverse biota is characterised by 43 species of true mangroves, plus many mangrove-associated plant species. Three mangrove species are in the IUCN Red List of Threatened Species: Sonneratia griffithii, Bruguiera hainesii and Heritiera fomes. Mangroves in this province had a mapped extent of 4,938 km2 in 2020, representing 3.4% of the global mangrove resource by area. The Andaman mangroves are threatened widely by wood extraction, encroachment and conversion for agriculture or aquaculture, and by coastal infrastructure projects in more specific locations. They also face threats from climate change, mainly in the form of sea-level rise (SLR), especially along the northwest coast of Sumatra. The Andaman mangrove ecosystem is thought to have undergone a major decline in extent around the early 20th century. Today the ecosystem covers 16% less than our broad estimations for 1970 based on national studies. However, the net area loss since 1996 is only -1.2% and there has been a further deceleration in area loss since 2015. Under a mid-high SLR scenario (IPCC RCP6) ≈21% of the Andaman mangroves would be submerged by 2070. Moreover, we estimated that 1.6% of the Andaman mangroves are undergoing degradation and this could rise to 5% over a 50-year period based on an analysis of the decay of vegetation indexes. These estimates are very conservative; however, there were no other data sources available to measure environmental degradation at the province level. Overall, the status of the Andaman mangrove ecosystem is assessed as Least Concern (LC).