Restoring Seaweed and Seagrass for Climate and Economic Benefits
Across Japan, initiatives are underway to restore seaweed and seagrass populations, not only to combat climate change through carbon capture but also to improve fisheries resources and seawater quality. This approach, known as blue carbon, has gained traction with the establishment of a framework for trading blue carbon credits.
The Japan Blue Economy (JBE) Association has been certifying blue carbon projects since 2020, issuing J Blue Credits based on the amount of CO2 absorbed. These credits can be sold to companies seeking to offset their carbon footprints, providing financial support for the restoration efforts.
One successful example is the Mashike fisheries cooperative association's collaboration with Nippon Steel Corp. to rebuild a local seaweed population. By burying iron slag in coastal areas, they provided the necessary iron for the growth of konbu kelp. This resulted in a fivefold increase in the seaweed colony and a significant boost in sea urchin catches.
Inspired by this success, similar initiatives have been implemented in over 50 locations nationwide, including the transplanting of eelgrass seedlings in Yokohama Port and the development of a tidal flat for growing sea lettuce in Kobe.
However, challenges remain in accurately measuring and evaluating blue carbon. Unlike trees, seaweed and seagrass do not store absorbed carbon permanently, making it difficult to assess their long-term impact. Additionally, standardized methods for measuring seaweed beds and weights are lacking.
To address these challenges, the Japanese government has proposed a technique to estimate seaweed colony size using satellite images and other data. They have also developed a method for calculating CO2 absorption for different types of seaweed and seagrass.
With these advancements, Japan aims to become the first nation to present details of its blue carbon absorption to the United Nations in April 2024. This initiative could pave the way for the development of global criteria for blue carbon, further promoting the restoration of these valuable marine ecosystems.