Saving the Seaweed: Japan’s Plans to Restore Important Marine Ecosystems

Discover how Japan is harnessing the power of seaweed to combat some global issues.

Seaweed is a staple of Japanese cuisine and a healthy food, rich in vitamins, minerals, fiber, and other important nutrients. Beyond its benefits as a food, seaweed provides homes to countless fish and marine species, and is a carbon sink, absorbing carbon dioxide from the atmosphere at faster rates than forests on land. This contributes to what is known as “blue carbon,” which refers to carbon stored in coastal and marine ecosystems such as seagrasses, mangroves, and seaweed. Recognizing the importance of seaweed in addressing climate change, maintaining ocean health, and supporting livelihoods, companies, local governments, and nonprofit organizations in Japan are working to protect and restore these vital resources.

Japan’s blue carbon initiatives

Japan is a global leader in blue carbon initiatives, leveraging its extensive coastline to combat climate change. These projects focus on restoring and cultivating coastal ecosystems like seagrass beds and seaweed farms, which are highly effective at absorbing and storing CO2. These efforts are often led by local governments and fishery cooperatives. To support them, the government has established the J-Blue Credit system, which allows companies to offset their emissions by investing in these natural carbon sinks, creating a financial mechanism for conservation.

Urchinomics: Restoring kelp fields for fish and creating jobs for coastal communities

Brian Tsuyoshi Takeda founded the company Urchinomics in 2017 after discovering a disturbing trend in coastal waters. There were sea urchins—everywhere. Due to the overfishing of predator species, these unassuming spiky little balls had been left to breed and multiply unchecked. Because sea urchins graze on kelp and other types of seaweed, this overpopulation has turned former kelp forests into barren undersea deserts.

The urchins themselves suffer too. Once they have eaten all the kelp, they begin to starve, becoming little more than hollowed-out husks. Therefore, sea urchin populations must be managed through regular thinning activities. While sea urchins are a delicacy in Japan and around the world, undernourished ones do not have enough meat to be marketable.

Urchinomics has a solution. The team farms and purchases these emaciated sea urchins, placing them in a closed and controlled on-land aquaculture facility, and feeds them for several weeks with proprietary specialized food until they fill up with creamy roe (uni). With renewed commercial value, they are then harvested and sold. In addition to conserving the marine environment, this creates sustainable jobs in coastal communities. Freed from overgrazing by sea urchins, the kelp forests can then regenerate within as little as three months. By thinning down the numbers of sea urchins in Oita and Yamaguchi Prefectures, where they have on-land ranches, and causing a revival of kelp and seaweed, Urchinomics has been recognized by the Japan Blue Economy Association for increasing CO2 sequestration.

Using waste products to fertilize seaweed beds

The small town of Suttsu in Hokkaido prospered in the early twentieth century due to its large catches of herring. However, the herring industry collapsed due to overfishing, climate change, and other reasons, forcing residents to find other ways to make their living from the sea. Awareness grew in Suttsu about the importance of regenerating coastal fish habitats. The Suttsu Fishery Cooperative Association has led local initiatives that use waste products as undersea fertilizer to encourage the regrowth of seaweed beds—a vital habitat for many fish species that can be caught and sold at market.

The waste used as seaweed fertilizer includes fishing byproducts, unused wood chips, and sewage sludge. A waste production facility in Suttsu composts these materials for 3–6 months, after which the compost is pressed into cylinders by a machine. These cylindrical blocks are then tossed from a boat into nearby coastal waters, where they sink to the bottom and decompose into the seabed, providing nutrients that encourage the seaweed to grow and the fish to come back.

Replanting and protecting seaweed beds

The seafloor off the coast of Shizuoka Prefecture was once blanketed by immense seaweed beds, some of the largest in Japan. By the 1990s, however, much of it had disappeared, reducing habitat for fish and other marine creatures.

In response, the local fisheries cooperative and other concerned parties joined forces to save the region’s seaweed beds. They used both direct planting of seaweed species such as sagarame and kajime as well as biodegradable bags of seaweed spores that were simply thrown into shallow water. Fish species known for grazing heavily on seaweed are targeted and eaten. Abalones have been reintroduced into the regenerated beds as a sustainable resource that creates jobs for local fisheries.

As these examples demonstrate, Japan is a global leader in harnessing the power of seaweed. By combining innovative projects with traditional knowledge and community-led efforts, the country is actively regenerating its coastal ecosystems, creating sustainable jobs, and combating climate change through the power of blue carbon.