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New evidence on coastal wetlands as carbon sinks

Marea E. Hatziolos's picture

In the corridors of COP 16 in Cancun last December, `blue carbon’ was being discussed in the context of Reduced Emissions from Deforestation and Forest Degradation (REDD+). The notion that wetlands and near-shore marine habitats constitute significant but largely unaccounted for natural sinks of atmospheric CO2 was just beginning to surface. Since then, there has been a surge in interest in Coastal Carbon Sinks, as evidence begins to mount on their ability to suck up CO2 and store it in their biomass and in deep sub-surface soil layers. A recently published study in Nature GeoScience cites evidence from field measurements that mangroves in Indonesia can actually store carbon at four times the rate of their terrestrial forest counterparts.

In contrast to terrestrial forests, mangroves and other wetlands store most of the carbon below ground, in a rich organic soil layer, which can run several meters deep. When this soil layer is disturbed—as happens when wetlands are drained or converted for other land use—huge amounts of carbon are released into the atmosphere in the form of CO2, and centuries or millennia of accumulated carbon can be emitted over the course of a few decades.

The extent of these emissions in estuaries and deltas, is highlighted in a detailed World Bank technical report. The preliminary findings of the report were summarized for decision-makers in a brief issued last December at the COP 16. The technical report, Mitigating Climate Change through Restoration and Management of Coastal Wetlands and Near-shore Marine Ecosystems: Challenges and Opportunities, is available on line and is being launched today in Indonesia at a Workshop on Tropical Wetland Ecosystems of Indonesia,in Bali.