78 JUNE 2025 • WORLD AQUACULTURE • WWW.WAS.ORG six core requirements for international recognition as blue carbon ecosystems.” These requirements include: • Scientific validation of seaweed’s CO2 absorption and carbon fixation mechanisms • Existence of quantifiable measurement standards and methodologies • Continuous field data monitoring systems • Reporting compatibility with international systems • Third-party verification capability The final requirement, the official listing in the IPCC greenhouse gas inventory guidelines, is pending. The agency stated, “We will be able to move to the next step if seaweed is included in the ‘methodological overview’ to be discussed at the IPCC-63 later this year,” and is compiling relevant data and submitting a formal proposal. Marine Sediments: The Deep Ocean’s Carbon Storage Marine sediments accumulate organic matter that settles naturally in the ocean, storing carbon long-term. Organic carbon from plankton, seaweed, and fish feces sinks to the seafloor, and some is fixed in sediments without decomposition. These structures are distinguished as “non-vegetation-based carbon sequestration ecosystems,” unlike tidal flats and seaweeds that directly absorb CO2 through vegetation. Professor Kwon Bong-Oh explained, “Tidal flats are intertidal zones where benthic microalgae photosynthesize and store CO2 in sediments, but marine sediments are always submerged and store carbon originating from plankton and others.” Internationally, the carbon storage potential of marine sediments is gaining attention. A 2013 paper by Carlos M. Duarte and colleagues, “The Role of Coastal Plant Communities for Climate Change Mitigation and Adaptation,” published in Nature Geoscience, found that about 50% of the world’s ocean organic carbon is stored in coastal sediments, with up to 1,000 tons of organic carbon stored per hectare in some areas. In Korea, related quantitative research has also begun in earnest. The Seoul National University Blue Carbon Project Group and Kunsan National University research team are establishing a measurement base by collecting seabed core samples, calculating organic carbon content, sedimentation rate, and density, and estimating the storage amount per unit area. They are promoting the expansion of the measurement range, reflecting the characteristics of each sea area. Professor Kwon emphasized, “What is more important than the absorption rate is how much carbon is deposited per unit area per year, and that becomes the standard for evaluating the sediment ecosystem.” This foundation aligns with discussions on international institutionalization. The 2022 report “Domestic and International Trends and Prospects of Blue Carbon” by the Ministry of Oceans and Fisheries and the National Institute of Fisheries Science classified sediments as new blue carbon candidate ecosystems alongside tidal flats and seaweeds, with scientific evidence gradually accumulating. South Korea has submitted a proposal to the IPCC based on the carbon storage potential of these ecosystems. If the methodology outline, which includes sediment ecosystems, is adopted at the IPCC-63 later this year, it will mark the first step toward institutional recognition. What Happens After IPCC Adoption? Suppose the methodology outline is adopted at the IPCC-63 later this year, which includes new blue carbon ecosystems such as tidal flats, seaweeds, and marine sediments. In that case, it will be the starting point for entry into the international system. However, outline adoption does not immediately mean institutionalization. The next step is developing a ‘formal methodology report’ that builds on the outline and organizes the detailed criteria. It includes a scientific description of how the ecosystem in question stores or absorbs carbon dioxide, specific formulas for measuring and calculating carbon stocks, criteria for correcting uncertainties, and guidance on applying these methods in the field. Development is led by the IPCC’s Task Force on Inventories (TFI), and the final report is the culmination of years of expert review and public comment. This report will then undergo the final approval process at an IPCC session, and the approved methodology will be transferred to the lower levels of the United Nations Framework Convention on Climate Change (UNFCCC). It can be applied when establishing each country’s NIR and NDC. In other words, countries will be able to calculate the carbon absorption in their ecosystems as official figures and report the reduction performance to the international community. Institutionally recognized carbon sinks will not only help achieve reduction targets but also open various policies and economic possibilities, such as carbon offset systems, international emissions trading, and climate fund linkages. For this reason, the institutionalization of blue carbon is an area directly linked to the possibility of actual assetization of carbon policy rather than a simple conceptual shift. Korea has currently submitted a methodology outline proposal to the IPCC, grouping three ecosystems: tidal flats, seaweed, and seabed sediments. The results of the 63rd Session of the IPCC, scheduled for the second half of this year, are likely to outline how each ecosystem will be reflected in international standards. It is expected to have a direct impact on the international status of the relevant ecosystem and the direction of domestic policy linkage. Notes Na, Jun Su (Reporter, HyundaeHaeyang https://www.hdhy.co.kr) https://www.hdhy.co.kr/news/articleView.html?idxno=31828 Marine sediments accumulate organic matter that settles naturally in the ocean, storing carbon long-term. Organic carbon from plankton, seaweed, and fish feces sinks to the seafloor, and some is fixed in sediments without decomposition. These structures are distinguished as “non-vegetation-based carbon sequestration ecosystems,” unlike tidal flats and seaweeds that directly absorb CO2 through vegetation.
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