Effects of climate change on mangroves relevant to the Pacific Islands

Pacific island mangroves include the world’s centre of mangrove biodiversity in Papua New Guinea, and extend east through all countries and territories as far as the Marshall Islands and Samoa. Mangroves provide many values to local communities, however immense worldwide losses have occurred in the past century owing to human coastal development, including around urban centres in the Pacific islands. There is limited published information on the current health and status of Pacific island mangroves. Mangrove seaward edge retreat attributed to relative sea level rise has been shown by spatial analysis between 1961-2003 in American Samoa, long-term mangrove zone retreat landward has been shown from the tectonically subsiding coastlines of SW Papua and Tikina Wai, Fiji, and Micronesian mangrove substrates are not keeping up with relative sea level rise, all indicating future mangrove loss with accelerated rates. Future effects of climate change on Pacific island mangroves could include mangrove mortality during unusually dry periods, and devastating impacts from the higher rates of sea level rise that are projected. There is agreement and consensus that potential impacts of projected sea level rise will be high on mangroves of the Pacific islands, and priority adaptation actions include promotion of mangrove substrate accretion and mangrove monitoring.