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Scientists identify how mangroves contribute to ‘blue carbon’ storage in Asia and the Pacific

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The soils of mangrove forests are able to retain large quantities of carbon. (Photo: N. Saintilan, Macquarie University)

Scientists in the Asia and Pacific region, with support from the IAEA, have successfully identified sources of carbon stocked in mangrove soils — an important step toward improving the management and restoration of wetlands.

Wetlands provide fundamental ecosystem services by acting as an efficient sink for atmospheric carbon, thus helping in the fight against climate change. Through photosynthesis, mangroves capture large amounts of atmospheric carbon and process it down through their roots, ultimately sequestering it in the soil of the wetlands. This organic carbon that is stored in marine ecosystems soils for periods of time, ranging from centuries to millennia, is known as ‘blue carbon’.

Wetlands are, however, vulnerable to anthropogenic and environmental changes, and their management and conservation is hindered by limited scientific information on ecosystem services. This is of particular concern in the Asia- Pacific region — the site of many of the largest wetlands in the world, including the Wasur National Park in Indonesia.

Carbon Released through Mangrove Loss

Mangrove loss in Indonesia has released considerable quantities of carbon stored in vegetation into the atmosphere, hindering ‘blue carbon’ sequestration in the soil. With support from the IAEA’s technical cooperation programme, scientists in Lampung Bay, Indonesia demonstrated the importance of mangroves in carbon accumulation. Samples were extracted from cores within the mangrove forest to determine the rate of carbon accumulation and carbon sources, using stable and radiometric isotopes.

Stable isotope analysis is used to quantify energy and nutrient flow and food web dynamics, in particular in wetlands. The techniques employ the elemental composition and stable isotopes of both carbon and nitrogen and can show how much ‘blue carbon’ is permanently sequestered and stored in wetland soils, where this carbon is sourced from, and the implications for greenhouse gas emissions.

“The wetlands programme provided world-class training opportunities for wetland scientists and practitioners in the Asia-Pacific region. By sharing expertise in the application of isotopic techniques to wetland management, participants gained insight into threats to wetlands and how these might be ameliorated,” said Neil Saintilan, an expert from the Department of Environmental Sciences of Macquarie University of Australia.

Better Management of Wetlands

In Thailand, a survey of the wetland carbon resources of Thung Kha Bay in the Chumphon Estuary was conducted with the support of the IAEA. Scientists determined the provenance of ‘blue carbon’ by comparing isotopic signatures of soil samples with those of the mangroves’ biomass’ carbon production. The findings revealed that the ‘blue carbon’ stored in the soil as organic matter was mainly sequestered by C3 plants, such as the red and loop-root species of mangrove. The results indicated that the mangroves of Thung Kha Bay are drawing considerable quantities of carbon from the atmosphere and preserving it within the rich organic soils of the mangrove forests.

“Through this project, more than 100 scientists in Asia and the Pacific have been trained to apply isotopic techniques to better understand and manage their wetlands. The IAEA technical cooperation programme supports countries to build capacity in the peaceful uses of nuclear science,” said Deng Ge, Director of the IAEA Department of Technical Cooperation Division for Asia and the Pacific.

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