Coastal blue carbon ecosystems, including mangroves, salt marshes, and seagrass beds, have efficient carbon dioxide sequestration capabilities, so protecting and restoring these ecosystems has become an important “nature-based solution.”
China’s coastal blue carbon ecosystem has a total area of 1.44 million hectares and a carbon storage of up to 118 Tg. Among them, the total carbon storage of mangroves is about 6.9 Tg; the total carbon storage of seagrass bed ecosystem is about 1.4 Tg, which is much lower than the total carbon storage of salt marsh wetlands, which is about 25 Tg. In addition, my country has a vast area of coastal beaches that are not covered by vegetation, and the total carbon storage is as high as 27~85 Tg.
In addition to carbon storage, the carbon burial capacity of these coastal blue carbon ecosystems also deserves attention. The total carbon burial amount of China’s mangroves is about 0.05 Tg/yr, the total carbon burial amount of seagrass beds is 0.01~0.02 Tg/yr, and the total carbon burial amount of salt marsh wetlands is 0.50 Tg/yr; the total carbon burial amount of China’s coastal beaches without vegetation coverage is 0.28~1.5 Tg/yr.
Coastal blue carbon systems usually have very low methane emissions, but under certain special circumstances, such as low salinity, they can also emit a certain amount of methane. The total methane emissions from China’s mangroves are 0.01 Tg/yr,
Currently, human activities have led to the loss of large amounts of coastal blue carbon ecosystems. In the 20th century, global coastal wetlands decreased by 25% to 50% due to human activities. Since 1950, the total area of mangrove forests in China has been reduced by half. In 2021, China planned to restore mangroves to 48,650 hectares in the next 10 years, which is expected to further absorb 0.1 Tg of carbon per year.