Written by Yuya Yokoyama

Have you ever heard of the remote island of Teuri Island in Hokkaido?

Many people outside of Hokkaido have probably never heard of or seen the name. Since moving to Hokkaido from Honshu, I too had seen the name of the island, but I had no idea what it was like. Suddenly, I had a chance to visit Tenuri Island.

The opportunity to visit Amauri Island was provided by Mr. Toshikuni Okamura, professor emeritus at Hokkaido University of Science and Director of the NPO Near-natural Forest Growing Association, who serves as an advisor to the project. Mr. Okamura has long been involved in activities to restore diverse forests close to nature, and I was invited to participate in the “Teuri Island Support Project,” which is spearheaded by him.

When I looked up what kind of island Teuri Island is on the Internet, I found that it is a “seabird paradise,” a globally precious island where humans and seabirds coexist in harmony. It would be a rare chance to visit such an island. At the same time, however, I also saw articles that addressed the serious problems facing the island, such as “forest and water shortages,” “declining seabird population,” and “declining population and depopulation.

At the same time, I felt that Mr. Okamura's method of forestation, “near-natural forestation,” would be suitable for resolving the problems of Teuri Island. I would like to explain the specific problems facing Teuri Island, using “forests and water shortage” as an example.

Water shortage from lack of forests

Teuri Island was facing a serious water shortage problem that was affecting the daily lives of the islanders. The root cause of this water shortage is believed to be the fishing industry. During the Edo period (1603-1867), full-scale herring fishing began in Hokkaido. Herring fishing spread to Amauri Island and flourished. When the fish oil produced when herring are boiled is squeezed out, “dregs” (i.e., “herring meal”) are produced, and these “dregs” have been found to be effective as a fertilizer. However, in the process of boiling the herring, a large amount of firewood was required. In order to secure firewood, the island's forests were cut down, and many forests were lost during the Meiji period. In addition, forest fires broke out during the Meiji and Taisho periods, and in 1884, logging was banned on the island, but it was already too late, and the forests on Amauri Island were in danger of disappearing.

Why does deforestation lead to water shortages? One might wonder about the cause-and-effect relationship. It is because forests have the “power to store water. Due to the movement of roots and other factors, the soil in forests tends to have openings, allowing water to soak into the soil like a sponge and store water. Rainwater stored in the soil can gradually move and flow into rivers. It also moderates the amount of water that flows into rivers and can prevent floods and landslides. These functions of forests are called “water source recharge functions. It is easy to understand why forests are called “green dams. Conversely, when forests are small, rainfall runs off the surface of the ground and into the ocean, and water cannot be stored. In other words, forest conservation is essential to alleviating water shortages.

The Teuri Island's erosion control project began after deforestation was banned; about 1,000 larch trees were planted in 1895, and as many as 250,000 trees were planted during the first half of the Taisho Era (1912-1926). In 1954, a windbreak forest development project was initiated as part of a public reforestation project, but the project failed to produce the expected growth due to poor soil, falling trees caused by seasonal winds, cold wind damage, and feeding damage by rats. The project was to be implemented for six years starting in 1980, using guiimatsu and todo firs. This led to an increase in the amount of forest on Amauri Island, which improved the soil's ability to retain water and, combined with the development of groundwater, helped to solve the problem of water shortages.

Recently, however, this problem is resurfacing. The forests that have been created so far on Amauri Island are overcrowded with a single species of coniferous tree. In addition, the forests have not been cared for, and the response has been delayed, resulting in many fallen trees caused by typhoons and other strong winds. If this problem continues unchecked, there is a strong possibility that the forest will return to its previous state of under-forestation and the water source will be depleted once again.Continuous forest conservation is necessary to protect this globally precious “seabird paradise."

Therefore, in 2016, the “Teuri Island Support Project” was launched.

In an effort to transform an overcrowded forest of a single conifer species into a diverse and stable forest, Mr. Okamura's reforestation method, “cultivated tree management,” will be implemented, and the overcrowded forest will be thinned using suitable methods. In addition, a sea kayak boatyard and sauna hut will be built on Teuri Island using the thinned timber, and efforts to enrich the lives of the islanders will also be implemented. The “Teuri Island Support Project” has had a far-reaching positive impact not only on forest development, but also on the culture of the islanders.

In addition, for the bare forests on Amauri Island, Mr. Okamura's “Ecological Mixed Seeding and Mixed Planting Method,” which is a series of mixed forest creation processes starting from seed collection as a single system, has been introduced to promote reforestation with biodiversity and sustainability, and activities for the future of Teuri Island are ongoing.

I have been a member of the “Teuri Island Support Project” since 2024. The scenery of Teuri Island was very moving and breathtaking, but more than that, I was personally moved to be confronted with the many people working hand in hand with the islanders in a cooperative manner to ensure the island's continued existence.

I plan to report regularly on the specific activities of the “Teuri Island Support Project” in the “to The Earth” activity report. We hope to expand the scope of our activities, not only in Hokkaido, but throughout Japan.