Noboribetsu Primeval Forest

Noboribetsu Primeval Forest: An Old Woodland Around Hell Valley

In 1924 the woodland wrapping the volcanic gorge at Noboribetsu was placed under national protection, making it one of the first natural monuments designated in Hokkaido. The Noboribetsu Primeval Forest (Noboribetsu Genshirin) covers roughly 186 hectares of slopes around Jigokudani, the explosion crater that supplies one of Japan's most productive hot spring resorts.

Walk a short way from the steaming crater rim and the sulphur in the air gives way to the damp, cool breath of an old broadleaf forest. The two sit side by side: a raw volcanic landscape on one hand, a quiet stand of mature trees on the other.

The forest lies in the southwestern corner of Hokkaido, in the Iburi region, about an hour by car from New Chitose Airport. The whole area falls within Shikotsu-Tōya National Park.

Why a Forest Became a National Monument

The Agency for Cultural Affairs records list the property simply as Noboribetsu Genshirin, designated on December 9, 1924, under criterion (2): a representative primeval forest with a rare forest flora. A portion was released from protection in 1959, and in 1984 the boundaries were adjusted again, with both an addition and a partial release.

The reasoning behind the designation is botanical. Southwestern Hokkaido is the mildest part of the island, and the early survey reports singled out this forest for being comparatively rich in warm-temperate species, with an unusually varied plant composition for a woodland this far north. Trees and herbs that one would expect further south grow here alongside the hardy broadleaf species typical of the region, and that range of plant life within a single stand is what set it apart.

Protection has continued under other systems as well. The Forestry Agency manages the same ground as the Noboribetsu Onsen Scenic Forest, and in 2018 it established the Noboribetsu Mizunara Rare Population Protection Forest over part of the area, recognising the value of its mature oak stands.

What to Notice on a Visit

The structure of the forest

Surveys have recorded about 60 kinds of trees and around 110 herbaceous plants here. The canopy is led by Mizunara oak (Quercus crispula), the trees reaching 15 to 19 metres with trunks 20 to 40 centimetres across, mixed with hōnoki (Japanese bigleaf magnolia) and shinanoki (Japanese linden). Below them grow rowan, koshiabura and other smaller trees, then a shrub layer of aodamo and ōkamenoki.

The forest floor tells its own story. Across much of the ground a dwarf bamboo called kumaizasa forms a dense green carpet. Where it thins out, you can spot young oaks, maples and Japanese yew pushing up, along with ferns and woodland herbs such as miyamakinutasō. This is a working forest in the ecological sense: old trees, saplings, ground cover and decay all visible at once.

The volcanic edge

Jigokudani, the "Hell Valley", is the forest's dramatic neighbour. The crater measures about 450 metres across and roughly 11 hectares, and it discharges close to 10,000 tonnes of hot water a day from countless vents and fumaroles. The bubbling, steaming ground gave the place its name, and the springs here feed the hotels of the town below.

A short walk away is Ōyunuma, a steaming pond whose surface sits at around 40 to 50 degrees Celsius. Below it, the Ōyunuma River carries hot water downstream until it cools to a comfortable temperature, where a free natural footbath has been set among the trees. Hiyoriyama, a small peak that still lets off white steam, rises nearby.

Walking it through the seasons

Boardwalks and footpaths link the crater, the pond and the footbath, so the forest is best experienced on foot rather than from a viewpoint. Fresh green arrives in May and June, autumn colour comes through October, and winter brings snow, though this part of Hokkaido sees relatively little of it and the climate stays mild by the island's standards.

Getting There and Practical Notes

From Sapporo, a limited express train reaches Noboribetsu Station in a little over an hour. From the station, a Donan bus runs to the Noboribetsu Onsen stop in about 15 minutes, and the trailheads sit a short walk from the hot spring town. By car, it is roughly 10 to 15 minutes from the Noboribetsu-Higashi interchange on the Dōō Expressway.

Paid car parks serve Jigokudani, and a separate car park near Ōyunuma closes through the winter. The Noboribetsu Park Service Center can help with maps and current trail conditions. In the warmer months, ticks are present in the undergrowth, so long sleeves and long trousers are sensible, and it is worth checking your clothing after a walk.

Nearby

The town itself is built around the hot springs and is easy to explore on foot. Noboribetsu Bear Park, reached by a cable car from the main street, keeps around 80 brown bears and includes a museum on the species. Noboribetsu Date Jidaimura recreates an Edo-period townscape with performances by actors playing samurai, ninja and other figures.

Along the Gokuraku shopping street, statues of oni (demons) tied to the "hell" theme stand among the shops, and the Enma-dō hall stages a short mechanical performance through the day. Lake Tōya, with its caldera scenery and lake cruises, lies within reach for a longer outing.