Donald Macintosh, Ena Suarez, Luzhen Chen, Pham Hong Tinh, Maeve Nightingale, Marcos Valderrabano

The 'Mangroves of South China Sea' is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology in the South China Sea province. It includes intertidal forests and shrublands of the marine ecoregions of the Gulf of Tonkin, South China Sea Oceanic Islands and Southern China. The diverse biota of this ecoregion is characterised by 42 species of true mangroves, plus many associated taxa. There is a significant decline in species diversity with increasing latitude towards the northern limit of mangroves in Fujian Province. Two species: Avicennia rumphiana and Camptostemon philippinensis are in the IUCN Red List of threatened species. The South China Sea ecoregion mangroves are mainly scattered open coast and estuarine formations, except in the Red River Delta. Their mapped extent in 2020 was 543 km2 representing only 0.4 % of the global mangrove resource. The current threats to mangroves are mainly from coastal urbanisation and industrialisation, sea dyke construction, pollution, and climate-related impacts, especially from typhoons, which occur frequently in this province. Today, the South China Sea mangroves cover ≈36 % less than in 1970 based on national studies. The South China Sea mangroves are also threatened by sea-level rise (SLR). Under a mid-high SLR scenario, and considering the limited coastal sediment supply, 50% of the mangrove area will be submerged by 2070. Moreover, we estimate that ≈5 % of the mangroves are undergoing degradation. Based on analysis of the decay of vegetation indexes, this could rise to ≈10 % over a 50-year period. These estimates are very conservative; however, no other data sources were available to measure environmental degradation at the ecoregion level. Considering the significant effect of future SLR, the South China Sea mangroves are assessed as Endangered (EN).