Rising sea levels threaten to drown mangrove forests, says study

Mangrove forests around the Indo-Pacific region are at risk of being submerged by 2070, an international study reveals. Those located in Thailand, Sumatra, Java, Papua New Guinea and the Solomon Islands are particularly in danger, the researchers claim.

Intertidal mangrove forests occur on tropical and subtropical shorelines, providing a wide range of ecosystem services to fisheries, in coastal protection and in carbon sequestration. The study, which appeared in the journal Nature, cited that mangrove forests are particularly vulnerable even with relatively low sea-level rises.

“The Indo-Pacific region holds most of the world’s mangrove forests, but sediment delivery in this region is declining, due to activities such as dam construction. This is of particular concern as this region is expected to have variable but high rates of future sea-level rise,” says Professor Catherine Lovelock, an ecologist at the University of Queensland.

She notes, however, that the outlook in other parts of the world is more positive. Their modelling, according to her, shows mangroves are likely to persist in east Africa, the Bay of Bengal, eastern Borneo and north-western Australia. These are areas where there are relatively large tidal ranges and/or higher sediment supply, Lovelock says.

Mangrove forests, even with an accumulation of sediment and maintenance of wetland soils, have the capacity to avoid inundation and keep pace with sea-level rise, Lovelock explains. However, she says there is an urgent need to plan for the maintenance of sediment supply in river systems that were likely to be dammed or heavily modified in future.

Forest degradation has to be reversed because it reduces organic inputs to soils that are vital for mangrove survival, Lovelock adds. Plans should be made for the landward migration of vulnerable mangrove forests to higher elevations.

For the study, the researchers analysed trends based on data from an international network of 27 sites. Sea-level rise could threaten the long-term sustainability of coastal communities and of valuable ecosystems such as coral reefs, salt marshes and mangroves, Lovelock says.

According to the World Wide Fund for Nature, or WWF, mangrove forests are one of the world’s most threatened tropical ecosystems. In its web site, the group says that more than 35 percent of the world’s mangroves are already gone. WWF cited climate change as among the threats to mangrove forests and their habitats, since mangrove forests require stable sea levels for long-term survival. They are extremely sensitive to current rising sea levels caused by global warming and climate change, the WWF says.

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