Children participating in the Japanese seagrass planting activity. (©Mika Sugiura)
On July 12, a hands-on event was held in Yokosuka City where participants planted Japanese eelgrass (Zostera japonica) in the sea. The event aimed to combat the "desertification" of coastal waters and raise awareness of marine conservation among children and their families.
Participants first learned about the important role of seagrass and seaweed beds, often called the "cradle of the sea." They then planted eelgrass seedlings themselves. The event marked the first joint initiative by the Miura Peninsula Blue Carbon Meeting, a partnership between five municipalities in the region.
Around 100 participants and staff from across the Miura Peninsula gathered at Recycling Plaza Aicle, a coastal processing facility in Yokosuka City. Normally closed to the public, the area is home to a preserved eelgrass habitat. It is one of the few remaining natural coastal areas in Tokyo Bay.
Protecting the 'Nursery of the Sea'
"Beds of eelgrass, such as common and Japanese eelgrass, serve as feeding grounds for small fish, shrimp, and crabs. They also provide shelter from predators. They truly are the nursery of the sea," said Dr Toshitame Imai, a fisheries scientist, as he gently addressed the children using educational panels.
Dr Imai explained that eelgrass and seaweed beds — including species like arame (Eisenia bicyclis) and kajime (Ecklonia cava)— once covered hundreds of hectares in Tokyo Bay and Sagami Bay. However, environmental degradation and rising sea temperatures due to global warming have increased the appetite of herbivorous fish such as aigo (rabbitfish). This has led to overgrazing. As a result, over 90% of these beds have disappeared, contributing to a phenomenon known as isoyake, or "rocky-shore denudation."
"Seaweed beds not only provide vital habitats for marine life," Dr Imai added, "they also help absorb and store carbon dioxide through photosynthesis." He emphasized their role in combating climate change through what is known as blue carbon.
Planting the Seedlings
After the presentation, the children carefully wrapped the eelgrass seedlings in water-soluble, eco-friendly paper clay to help anchor them in the seabed.
"I pretended I was a fish and tried biting the eelgrass," laughed 10-year-old Youya Watanabe, a fourth grader from Hayama Town. "But it was bitter and tough." He often visits the local beach and showed keen interest in the activity.
Establishing a Regional Partnership
In May 2024, the cities of Yokosuka, Kamakura, Zushi, and Miura, along with Hayama Town, established the Miura Peninsula Blue Carbon Meeting.
Blue carbon refers to carbon captured and stored by coastal ecosystems. These include eelgrass beds, seaweeds like wakame, and phytoplankton, all of which absorb carbon dioxide through photosynthesis. The concept was introduced in 2009 by the United Nations Environment Programme (UNEP) as a promising tool in the fight against climate change.
Each municipality had previously addressed coastal degradation on its own. Efforts included controlling species like sea urchins and aigo, which damage seaweed beds. Now, by sharing knowledge and collaborating, the municipalities aim to restore coastal ecosystems more effectively and promote blue carbon initiatives.
Since 2024, Yokosuka City has organized seagrass planting events for children in cooperation with the local nonprofit Yokosuka Sea Citizens' Council. This most recent event was the first held jointly by all five municipalities. With promotion from each city and town, it attracted a wide range of participants, including many from Hayama. The turnout reflected growing regional cooperation.
Into the Sea
The children moved to a shallow coastal area behind the Aicle facility. Using shovels, they dug into the seabed and carefully planted the seedlings they had wrapped earlier. Their faces showed deep focus and determination.
After planting, the children explored the sea using box goggles. When a net was swept through the seaweed bed, they discovered cuttlefish eggs, prompting cheers of excitement.
Exploring Marine Life
Some of the Japanese eelgrass planted in 2024 had already taken root. The sight of the plants swaying underwater gave participants a clear sense of the impact of their efforts. The Sea Citizens' Council has been working for three years to restore seagrass and seaweed beds, including Japanese eelgrass. These now cover about 270 square meters.
"Even though we live on a peninsula surrounded by the sea, some children have never played in it or even touched it," said Masato Kawaguchi, the council's representative. "We hope these kinds of experiences help kids feel a connection to the ocean, see that marine life is returning, and start thinking about environmental issues."
A Carbon-Neutral Future
In October 2020, Japan declared its goal of achieving carbon neutrality by 2050. The four cities and one town of the Miura Peninsula have made the same pledge. They are now working to accelerate their climate action.
A central pillar of this effort is a subsidy program supporting the installation of solar panels and storage batteries. Yokosuka City applied for funding through the environment ministry's Priority Measures Acceleration Project. Together with the other municipalities, they secured ¥1 billion (about $6.8 million USD) in subsidies over five years.
The program provides financial assistance to individuals and businesses for installing solar and battery systems. This reduces upfront costs and encourages wider adoption. Applications for the current fiscal year are open until January 15, 2026, with subsidies continuing through 2028.
If fully utilized, the initiative is expected to add about 9,000 kW of renewable energy over five years. It could reduce carbon emissions by 110,000 tons of carbon dioxide, equivalent to the annual emissions of roughly 1,600 households.
A Model for the Nation
The environment around us is changing rapidly. Population decline, climate change, and intensifying natural disasters are becoming more urgent issues. While each person's actions may seem small, collective effort and awareness are essential. Cooperation across municipal boundaries is key to solving global challenges.
"We used to be limited when it came to activities outside our city," said Kawaguchi. "But the ocean is all connected. Being able to work across jurisdictions is a major step forward."
Yokosuka Mayor Katsuaki Kamiji, who initiated the regional collaboration, echoed that message:
"We're committed to working together to pass down our rich seas and natural environment to future generations."
The Miura Peninsula's unified approach could become a model for communities across the country.
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Author: Mika Sugiura
