In the fight against climate change, Japan is looking to seagrass for carbon capture

Yokohama, Japan: Last Saturday, about 100 volunteers gathered at a popular beach in the Japanese port city of Yokohama, where they waded through the shallow water to plant strands of pale green seagrass on the seabed.

What started as a project to restore the natural ecosystem along the coast of the city just south of Tokyo has taken on a national importance: helping combat climate change as Japan strives to achieve carbon neutrality by 2050.

Japan, the world’s fifth largest emitter of greenhouse gases, covers a smaller area than California but has some of the longest coastlines in the world. That makes marine vegetation a viable method of capturing at least a fraction of the carbon dioxide it produces, scientists say.

“Over the course of this work, we’ve come to understand that it can absorb and store the carbon that causes climate change,” said Keita Furukawa, a marine scientist at the Association for Shore Environment Creation.

In a world first, Japan’s latest annual greenhouse gas inventory, provided this month to the United Nations Framework Convention on Climate Change (UNFCCC), included carbon absorbed by seagrass and seaweed beds in its calculations.

The Ministry of Environment estimates that in the 2022 financial year, the amount of blue carbon – carbon naturally stored by marine and coastal ecosystems – was around 350,000 tonnes.

While that’s just 0.03 percent of the 1.135 billion tons of CO2 equivalent greenhouse gases Japan emitted that year, blue carbon has become increasingly important as the country’s forests age and absorb less carbon dioxide than younger trees.

The amount of greenhouse gases absorbed by forests has fallen by 17 percent in the five years to 2022, government data shows. Japan has said it will make efforts both on land and in the sea to sequester more carbon.

“If seagrass grew in every shallow part of the sea, it is possible that it would grow. I think it could absorb maybe 10 to 20 percent of human emissions,” Furukawa said.