IUCN Red List of Ecosystems, Mangroves of the Western Coral Triangle

Abstract

The 'Mangroves of the Western Coral Triangle' is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology. It includes intertidal forests and shrublands of the following marine ecoregions in the Western Coral Triangle province: Banda Sea, Eastern Philippines, Halmahera, Lesser Sunda, Northeast Sulawesi, Palawan/North Borneo, Papua, and Sulawesi Sea/Makassar Strait. The diverse biota of this province includes 48 species of true mangroves, plus many mangrove-associated taxa. Mangroves had a mapped extent of 19,821 km2 in 2020, representing 13.4% of the global mangrove resource by area.Although only 4.7 % of the province’s mangroves occur on carbonate sediments, they include fragile patches of vegetation on many of the thousands of islands in the Western Coral Triangle, Mangroves are threatened by illegal logging, conversion for agriculture or aquaculture, and industrial, urban and tourism development, including coastal land reclamation and mining. They are also threatened by climate change, especially sea-level rise, and by increasingly frequent typhoons and tropical storms.Today the Western Coral Triangle mangroves cover ≈32% less than our estimate for 1970 based on national studies. The rate of loss declined to -6.6% from 1996 to 2020 and has slowed further since 2015. The Western Coral Triangle mangroves are estimated to decrease by -18% over the next 50 years. They are also threatened by future sea-level rise (SLR). Under a mid-high to extreme SLR scenario, more than 30% of the mangroves would be submerged by 2070. Moreover, we estimate that 4% of the mangroves are undergoing degradation and this could rise to 10.7% over a 50-year period based on analysis of the decay of vegetation indexes. These estimates are very conservative; however, no other data sources were available to measure environmental degradation at the province level.Overall, the Western Coral Triangle mangrove ecosystem is assessed as Vulnerable (VU)