【Landscape of the Yunomaru Highland】
Jōshin’etsu-kōgen National Park, Japan’s second largest national park, spans the prefectures of Gunma, Niigata, and Nagano. Established in 1949, the park encompasses 148,194 hectares of mountain forests and high-altitude plateau land, including two active volcanoes. This expansive territory contains a wide range of habitats that support abundant and varied wildlife.
The Yunomaru Highland lies at the southern end of the park, among the western peaks of the Asama-Eboshi volcanic range. The highland was formed by volcanic activity between 1 million and 100 thousand years ago. It stretches from Mt. Eboshi (2,066 m) and the twin peaks of Mt. Yunomaru in the west to Mt. Nishi-Kagonoto (2,212 m), Mt. Higashi-Kagonoto (2,228 m), and Mt. Mizunoto (2,202 m) in the east. Between these peaks are plateaus that vary in elevation between 1,700 and 2,000 meters, a range that is generally considered subalpine. However, due to an unusual interplay of geological and climatic factors, the plateaus support ecosystems that are usually seen at much higher elevations.
The annual temperature differential of the Yunomaru Highland is relatively high: temperatures average 21 degrees Celsius in summer and negative 5 degrees Celsius in winter. Cool air currents flow in from the Sea of Japan, creating heavy winter snowfalls. The snow that accumulates on the northern slopes protects forest growth from the freezing temperatures, but the mountains’ southern faces receive more sunlight. As the snow there melts, the collision of warm and cool air currents produces strong winds. Together, these conditions limit the vegetation that grows on the southern slopes to mostly shrubs and dwarf species.
