In the north of Japan, every winter, the slopes of Mount Zao They transform into an otherworldly landscape. Fir trees covered in frost and snow take on spectacular shapes known as juhyo or “snow monsters”: frozen giants that resemble ghostly creatures sculpted by the wind. This phenomenon, almost exclusive to the mountain range that separates Yamagata and Miyagi prefectures, constitutes a unique tourist and natural attraction.
Juhyo are not normal trees under the snow: they form when the winter west wind, loaded with droplets of supercooled water, hits the fir trees. Aomori todomatsu and causes gel to accumulate in increasingly thick layers. Over time, these accumulations take the form of overlapping ridges called “shrimp tails” which, when grouped together, create fantastic shapes that attract tens of thousands of visitors each year.
But this natural wonder is in decline. In August 2025, a team led by Professor Emeritus Fumitaka Yanagisawa from Yamagata University analyzed photographs of Mount Zao taken from the same position since 1933. The study observes a clear decrease in the thickness of the monsters over the decades: while in the 1930s they could reach between five and six meters wide, many formations since 2019 do not exceed half a meter or are even only narrow columns.
What is happening?
The cause of juhyo thinning is twofold. On the one hand there is global warmingwhich increased the region’s average winter temperatures (a phenomenon documented in various studies that indicate temperature increases in mountainous regions like Japan well above the global average) and shifted the climatic range suitable for the formation of these ice sculptures to higher altitudes.
On the other hand, the very trees that shelter the monsters are under attack. Since 2013, a moth infestation has stripped many spruce trees of their needles, weakening their ability to support ice sheets. Subsequently, bark beetles attacked these already weakened trees, causing the death of approximately 23,000 fir trees (about a fifth of the prefecture’s forests) according to official reports. With fewer branches and leaves, there is less surface area for snow and frost to adhere to form the massive monsters the area is famous for.
If the trend continues, experts warn that in increasingly warm winters, the juhyo phenomenon could completely stop forming towards the end of this centurysymbol of how climate change affects not only species or weather events, but also natural landscapes that for decades have been reliably spectacular.
Faced with this threat, the Yamagata authorities favored Juhyo Reactivation Conference (Juhyo Revival Conference), a permanent council that brings together researchers, residents, local businesses and governments to coordinate long-term efforts to restore spruce forests and preserve the phenomenon. Since 2019, more than 190 naturally regenerated trees have been transplanted to elevated areas, although this takes between 50 and 70 years to mature and regain their ability to generate juhyo.
The loss of snow monsters would also have a profound economic and social impact. They are a pillar of winter tourism in the Zao region, attracting visitors not only for skiing, but also for the opportunity to see a unique landscape. “If juhyo disappeared, it would be a big blow to the local economy,” says an official from the juhyo tourism association Zao Onsen.
In addition to official efforts, students and scientists are joining the fight: in Murayama, young people from technical schools are working to cultivate fir trees Aomori todomatsu and experimenting with propagation methods to ensure that, in the decades to come, there will be more trees capable of supporting these frozen figures.
Today, Japan’s “snow monsters” are not only a fascinating natural spectacle: they are a visible reminder of how delicate interaction between climate, forests and wind could be modified by global warming. Their protection is a challenge lasting several generations, and their future is closely linked to that of the forests which shelter them.
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