Blue Carbon is a term coined by analogy with Green Carbon — the carbon stored by terrestrial ecosystems — and refers to carbon that is captured and stored through marine ecosystems. This includes not only mangroves, trees that grow in coastal wetlands, but also tidal flats, marine wetlands, and underwater seagrass beds. Blue carbon is absorbed up to 50 times faster than green carbon and offers superior storage capacity.
Blue carbon gained significant attention at COP26 (the 26th Conference of the Parties to the United Nations Framework Convention on Climate Change) in 2021 as a key tool for responding to the climate crisis. From that point on, the importance of blue carbon conservation efforts also came to the fore — including Indonesia's mangrove forest restoration campaigns, South Korea's tidal flat management and restoration programs, and the expansion of marine protected areas across Latin America.
Mangrove Forests: Trees Rooted in Salt Marshes
Mangrove forests, with their distinctive vegetation growing in subtropical and tropical coastal wetlands, have been found to store up to five times more carbon than inland forests. However, ongoing ecological destruction driven by development pushed them to the brink of extinction. Today, many countries are dedicating considerable effort to managing mangrove forests for the dual purposes of sustaining rich marine ecosystems and addressing global warming.
Tidal Flats: Absorbing Carbon Dioxide
Tidal flats absorb more than 260,000 tonnes of carbon dioxide annually — equivalent to the greenhouse gas emissions of 110,000 vehicles. As the significance of tidal flats — vast repositories of rich Biodiversity — has been increasingly recognized, South Korea's tidal flats, among the five largest in the world, have also drawn considerable attention. While many of Korea's tidal flats were reclaimed or degraded by urban construction and port development, the government's Wetlands Conservation Act and tidal flat restoration projects are now actively protecting this vital blue carbon resource.
Seaweed: Blue Carbon Beneath the Waves
Marine seaweed also functions as blue carbon, absorbing approximately 6% of the total carbon captured by the world's forests. Companies with an interest in blue carbon are joining efforts to create ocean forests, and seagrasses — flowering plants known to bloom even in seawater — have emerged as particularly well-suited species for underwater forests. Seaweed absorbs carbon dioxide through photosynthesis and stores it in biological tissue and seafloor sediment. Once stored in this way, carbon does not re-enter the atmosphere, producing a near-permanent sequestration effect that makes a significant contribution to climate change mitigation.
The reason blue carbon demonstrates such high carbon storage capacity is that low oxygen levels in marine ecosystems suppress bacterial activity. In other words, when oxygen is scarce and the bacteria that decompose organic matter are inhibited, carbon dioxide is not released into the atmosphere but is instead stored in tidal flats and submerged plant matter and soil. This mechanism is the key factor enabling blue carbon to efficiently absorb and store carbon within ecosystems.
Blue carbon is also emerging as a critical resource for climate change response on economic grounds: the cost of planting blue carbon vegetation is approximately one-twentieth that of green carbon, with virtually no additional maintenance costs.
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by Editor O