The first national scale evaluation of organic carbon stocks and sequestration rates of coastal sediments along the West Sea, South Sea, and East Sea of South Korea.

Blue carbon science requires the estimates of organic carbon stock and sequestration rate; however, holistic data analysis remains limited in South Korea. The present study reports current organic carbon stocks and sequestration rates in the coastal areas of West Sea, South Sea, and East Sea of South Korea, encompassing entire intertidal areas using long-term field survey combined with remote sensing technology. Twenty-one intertidal flats were targeted across seven provinces (Gyeonggi, Chungnam, Jeonbuk, Jeonnam, Gyeongnam, Gyeongbuk, Gangwon). Out of the evaluated environmental parameters, mud content represented a significant factor controlling sedimentary organic carbon stocks across target areas, and was significantly positively correlated to the total organic carbon (p < 0.05). Organic carbon stocks measured in salt marshes (i.e., upper intertidal zone) reflected the high carbon fixation capacity of halophytes through primary production. Sediment textural type was classified using analysis of remotely sensed imagery, and was closely correlated to field-based classification data (p < 0.05). Using field and remote sensing results, we estimated total organic carbon stocks (13,142,149 Mg C) and sequestration rates (71,383 Mg C yr-1) in the tidal flats of South Korea. This study presents the first report on blue carbon potential in the Korean tidal flats, providing baseline information on the carbon dynamics of intertidal sediments in this region and, potentially, elsewhere.

Analysis of forty years long changes in coastal land use and land cover of the Yellow Sea: The gains or losses in ecosystem services.

The drastic land cover change and its impacts in the Yellow Sea have long been significant issues in terms of coastal vulnerabilities, but holistic data analysis is limited. The present study first reports 40 years long geographical changes of the Yellow Sea coasts including all three neighboring countries of China, North Korea, and South Korea. We delineated tidal flats by analysis of Landsat series satellite imageries (662 scenes) between 1981 and 2016. A total area of the Yellow Sea tidal flats has been considerably reducing for the past 36 years, from ∼10,500 km2 (1980s) to ∼6700 km2 (2010s), say ∼1% annual loss. A majority loss of tidal flats was mainly due to the grand reclamations that conducted in almost entire coast of the Yellow Sea, particularly concentrated in the 1990s-2000s. Coastal reclaimed area during the past four decades reached ∼9700 km2, including ongoing and planned projects, which corresponds to over half the area of precedent natural tidal flats of the Yellow Sea. The potential carbon stocks in the eight representative regions with large scale reclamation indicated significant loss in carbon sink capacity in the South Korea's coast (∼99%), while evidenced a lesser loss from the China's coast (∼31%). It was noteworthy that the progradation of tidal flats after the reclamation in China's coast significantly reduced the loss of carbon sequestration. According to the ecosystem services valuation for the Yellow Sea, a total loss was estimated as ∼8 billion USD yr-1 with relatively high proportional loss (up to 25%) of climate regulating services (viz., carbon sequestration). Overall, huge losses in ecosystem services being provided by the Yellow Sea natural tidal flats need immediate action to prevent or at least alleviate accelerating ecological deteriorations. Finally, future conservative policy direction on coastal wetlands management has been proposed towards enhancement of marine ecosystem services.