GLOSSARY OF SUSTAINABLE SEAFOOD

Blue carbon

Carbon stored in marine ecosystems such as mangrove forests, wetlands, tidal flats, and seaweed beds is called "blue carbon." It was named in a report by the United Nations Environment Programme (UNEP) in October 2009 in contrast to carbon absorbed by terrestrial vegetation such as forests, which is called "green carbon."

Carbon absorbed by the ocean from the atmosphere and land is eventually incorporated through photosynthesis into seaweeds such as mangroves, eelgrass, and sugamo, and seaweeds such as kelp and wakame. When these wither and die, the carbon is trapped and stored as it accumulates on the seafloor.

The oceans absorb roughly 55% of the CO released into the atmosphere.₂It is estimated that half to as much as 7% of this is absorbed by mangrove forests, tidal flats, seaweed, and seagrass. Although the amount of these biological resources is only 0.05% of that of plants, they absorb almost the same amount of CO as plants.₂It is known to absorb and is therefore a powerful sink.^*1.

The United Nations Framework Convention on Climate Change (UNFCCC) has also adopted a method for calculating blue carbon,₂It is permitted to calculate the reduction in^*2In 2021, Japan also, for the first time, calculated mangrove forest absorption when reporting greenhouse gas emissions and absorption to the United Nations.^*3.

Japan's blue carbon absorption is about 100 million tons^*4It is estimated that it can absorb up to 12% of the carbon dioxide absorbed by forests and farmland.^*4In the future, the number of forests that are over 40 or 50 years old will increase, and CO₂It is predicted that absorption will decrease, and blue carbon is expected to play an important role.

In response to these expectations, local governments across Japan are actively cultivating seaweed and seagrass to increase carbon absorption in marine ecosystems. For example, Fukuoka City and Yokohama City are cultivating eelgrass beds and wakame seaweed beds, and are reducing CO₂The amount of absorption and reduction is converted into credits and sold.^*5.

Cultivating seaweed beds not only serves as a carbon sink, but also purifies water and provides a place for marine life to spawn and nurse. This has benefits for the fishing industry as well. In cities such as Yokohama, wakame cultivation and harvesting events are held that involve children, and are used as educational projects. Blue carbon seems to have the potential to create a variety of values.