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Nuke disaster radiation continues to threaten traditional ways of life in northeast Japan

Tetsuzo Tsuboi, who has worked to prevent shiitake cultivation logs from absorbing radioactive cesium by putting them up on blocks, covering them with nonwoven fabric, and other measures, is seen in the Miyakoji district of Tamura, Fukushima Prefecture, on Sept. 5, 2021. (Mainichi/Rikka Teramachi)

FUKUSHIMA -- When the Fukushima Daiichi Nuclear Power Station was struck with a triple-meltdown in March 2011, it spewed radioactive material across a wide swathe of northeastern Japan's forests. Even now, more than a decade after the catastrophe, the impact of the cesium still found in the region's trees is enormous.

    One area to feel the brunt of the fallout's effects is eastern Fukushima Prefecture's Abukuma mountains, once one of Japan's leading sources of logs for shiitake mushroom cultivation, and now at a virtual standstill. Ten years into this continuing disaster, locals and experts have been working hard to find ways to revive the traditional industry, in hopes of being able to pass on the mountains' rich natural resources, and the life connected to this landscape, to the next generation.

    "Once a tree trunk gets this thick, it's not really good as a log." We are in the woods in the Miyakoji district of Tamura, Fukushima Prefecture, about 20 kilometers west of the Fukushima Daiichi plant. Kazuo Watanabe, the 59-year-old head of the Miyakoji office of the Fukushima central forestry union, is standing by a copse of konara oaks for shiitake cultivation, sighing as he speaks.

    Watanabe says that the oaks are harvested for the shiitake business when they are about 15 centimeters across. And it takes about 20 years to get that big. If the trunks are too thick, it becomes difficult for new growth to sprout from the stump. But konara logging has stagnated severely because of the nuclear disaster, leading to a halt in shipments.

    Radioactive cesium exceeding the government-set maximum of 50 becquerels per kilogram has been detected in logs from Miyakoji and other parts of the Abukuma region. Even 10 years after the Fukushima Daiichi reactor meltdowns, testing has turned up cesium levels in the logs of between 100 and 540 becquerels per kilogram.

    To grow shiitake, mushroom mycelia are put into holes drilled into sawtooth oak, konara oak and other types of logs. In 2010, Fukushima Prefecture was Japan's third-largest producer of these logs, shipping some 4.78 million of them. But the nuclear disaster changed all that, and even now the prefecture produces only about 140,000 of the cultivation logs annually.

    According to the Forestry Agency, as of the end of 2020, log-grown shiitake shipments were restricted in 93 municipalities across Fukushima, Iwate, Miyagi, Ibaraki, Tochigi and Chiba prefectures due to cesium contamination. Along with Fukushima Prefecture, Miyagi Prefecture and other jurisdictions are voluntarily limiting shipments of the logs as well.

    Cesium 134 has a radioactive half-life of about two years, meaning it has almost disappeared over the past 10. However, cesium 137's half-life is approximately 30 years, meaning it will retain 30% of its original radioactivity 50 years on from the disaster, and 10% after a century.

    The problem is the cesium inside the trees, which absorbed disaster fallout though their bark soon after the meltdowns, and through their roots. If plants have scant supplies of potassium, an essential element for growth, then they will absorb cesium, which has similar chemical properties. This has led to farmers sprinkling their fields with potassium fertilizer as a countermeasure. However, this is difficult to do in the vastness of the forest.

    About 70% of Fukushima Prefecture is covered in forest. But in principle, only certain areas are eligible for nuclear disaster decontamination, such as residential districts and their immediate surroundings. The government and researchers believe that decontamination has limited the effectiveness in reducing the external exposure of the residents and that it is very costly, plus there is a risk of a spillover of soil due to the scraping of topsoil. And while cesium 137 indeed becomes less radioactive over time, it will take 150 years for the emanations to fall to a few percent of its current level.

    And so the shiitake cultivation log production is essentially frozen, as are local traditions of sharing out edible wild plants, mushrooms and the like. To preserve these natural resources and this way of life for future generations, in January 2020 local forestry workers and experts created the "Abukumayama no kurashi kenkyujo," or the Abukuma mountain way of life research center. Its purpose: to create a vision for the Abukuma region for the next 150 years. Participants study woodland culture at former industrial sites connected to the mushroom cultivation log business. Research center head Kazunori Aoki, 60, told the Mainichi Shimbun, "The nuclear accident changed the mountains' value, and our connection to them has become quite tenuous."

    Aoki once raised "wagyu" beef cattle and farmed vegetables in Miyakoji, but he closed his business after the nuclear disaster. Watching growing tracts of farmland go wild, Aoki said he decided he "wanted to change the landscape a little at a time and return it to the mountains." Since 2012, he has been planting 100 to 300 maples and other trees every year, a project that helped lead to the Abukuma research center's creation.

    In April this year, the center brought together 40 people from both inside and outside the city of Tamura to plant 90 mountain cherries, Kobushi magnolias and other trees in Miyakoji. But some elderly residents of the district worry that there is no one to take over the community, and that there is no hope for a future connected to the mountains.

    "We want to work with the local community to consider how the next generation can live with the natural wealth of the mountains," commented center administrative head Yumeko Arai, 35.

    (Japanese original by Rikka Teramachi, Fukushima Bureau, and Shuji Ozaki, Minamisoma Local Bureau)

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