IUCN Red List of Ecosystems, Mangroves of the Northwest Australian and Sahul Shelf

Tertius de Kluyver, Norman C. Duke, Catherine E. Lovelock, Ena Suarez, Sean G. MCGregor

Mangroves of the Northwest Australia and Sahul shelf is a regional ecosystem subgroup (level 4 unit of the IUCN Global Ecosystem Typology). It includes the marine ecoregions of Arafura Sea, Arnhem Coast to Gulf of Carpentaria, Bonaparte Coast, Exmouth to Broome, Gulf of Papua, Houtman, Lesser Sunda, Ningaloo, Shark Bay, Southeast Papua New Guinea and Torres Strait Northern Great Barrier Reef. In 2020 the mapped extent of this province was 18061.4 km2 across, representing 12.3% of the global mangrove area. The biota is characterised by 50 mangrove plant species, including intermediates.
The province encompasses varied climates and geography, with habitats ranging from monsoonal coasts of southern New Guinea to arid western shores of northern Western Australia. A pronounced dry season (April–November) dominates, with 95% of river flow during the December–March wet season. Low-energy waves along northern Australia allow dense mangrove growth along nearly half the semi-arid tropical shoreline. In the Northern Territory, stands are woody and dense, extending inland along estuaries and exposed shores.
Today the Northwest Australia and Sahul shelf mangroves cover 95% of our broad estimation for 1970. However, the mangrove net area change has been -2.8% since 1996. If this trend continues an overall change of -6.0% is projected over the next 50 years. Furthermore, under a high sea level rise scenario (IPCC RCP8.5) ≈-7.6% of the Northwest Australia and Sahul shelf mangroves would be submerged by 2060. Moreover, 0.8% of the province’s mangrove ecosystem is undergoing degradation, with the potential to increase to 2.5% within a 50-year period, based on a vegetation index decay analysis. Overall, the Northwest Australia and Sahul shelf mangrove ecosystem is assessed as Least Concern (LC).