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Zao’s soft rime snowscape imperiled by widespread insect damage

Yomiuri Shimbun file photo

Zao’s soft rime seen from the Zao Onsen Ski Resort in Yamagata in January 2018.

The Yomiuri ShimbunYAMAGATA — The enchanting winterly view of the soft rime snowscape in Zao, Yamagata Prefecture, could soon be only visible in photos, as the trees that form the canvas of the mesmerizing scenery have been seriously damaged by insects.

Near the summits of the Zao range, the trees stand dead or dying, and the blight has spread toward the foot of the mountains. Soft rime will have slim chances to form if dead branches or trunks collapse due to the weight of the ample snow.

The central government will begin planting trees from fiscal 2019, but the reforesting project is considered by experts as “not easy to regenerate the art created by nature.”

Wind-blown water droplets from clouds over the Sea of Japan freeze on the coniferous trees, known as Aomori-todomatsu (Maries’ fir), growing on the Zao mountains. The supercooled water droplets freeze and accumulate on the trees’ surfaces along with snowflakes to form the fluffy appearance. The soft rime grows the most during late January and February, and the scenery is famously called the “Snow Monster.”

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  • The Yomiuri Shimbun

  • Courtesy of the Yamagata District Forest Office

    Aomori-todomatsu trees stand dead in this photo taken in October 2018.

  • Courtesy of the Yamagata District Forest Office

    A bark beetle

The Tohoku Regional Forest Office confirmed insect damage on the trees by 3-millimeter-long bark beetles for the first time in summer 2016. At that time, it found that 45 of 60 sample trees suffered beetle damage on the south side of the Zao Ropeway’s Jizo Sancho Station at altitudes between 1,500 meters and 1,660 meters above sea level.

In fiscal 2018, however, the damage was observed to have spread to all 60 sample trees, and the area of the damage extended downward to an altitude of 1,420 meters. An aerial investigation confirmed that all of the trees near the ropeway station — not just the sample trees — stood dead.

Hideaki Goto, a researcher at the Forestry and Forest Products Research Institute’s Kyushu Research Center in Kumamoto, said bark beetles tend to infest trees weakened by natural disasters and other causes. In Zao, damage of Aomori-todomatsu trees caused by palmerworm caterpillars was found in 2013. Goto said that bark beetles infested the trees that were already damaged by palmerworms, and propagated.

The Tohoku forest office and other groups will began replanting Aomori-todomatsu saplings — growing wild at low altitudes — out to the area near Jizo Sancho Station in a trial. Since the project takes place in the special protection zone of a quasi-national park, it requires permission from the Yamagata prefectural government, which controls the zone. The planting will be conducted very carefully in order to minimize the impact on the environment.

“We must rack our brains to regenerate the landscape despite several agitating factors, such as whether saplings can grow steadily in the difficult environment of high altitude,” said Hiroaki Funatsu, a coordinator of the Tohoku office’s Yamagata District Forest Office.

According to the Zao Ropeway operator, about 70,000 tourists come to the area every year to see the soft rime.

Zao hot spring tourism association chairman Hachiemon Ito said, “We request [experts] to take effective measures to pass down Japan’s treasure to the next generation.”

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