The Present and Future of Micronesian Mangrove Forests in the Context of Rising Sea Levels

In recent years, sea levels in the low latitudes of the north-western Pacific, including Micronesia, have risen much faster than the global mean. As a result, some mangrove communities on Pohnpei Island have already been visibly affected by surface erosion. On the other hand, Rhizophora communities, characterized by their prop roots, have barely maintained their habitat by producing and accumulating mangrove peat by themselves. Analysis of satellite imagery for Pohnpei, Kosrae, Chuuk and Yap shows no evidence thus far of simultaneous retreat of seaward forest margins or standing dead in surface erosion areas, but coastal erosion is already underway at some wave-sensitive sites. At the moderate rate of sea level rise predicted by the Intergovernmental Panel on Climate Change (IPCC) (approximately five millimetres per year), Rhizophora forests are likely to maintain their habitat. It is necessary to continue to monitor forest dynamics and to aggressively plant Rhizophora species on sites that have become bare land due to logging or trees being downed by typhoons.