Japan's permafrost in danger of disappearing ― Major changes in mountain environments inevitable in the next 20-30 years

Permafrost is an area where the temperature of the ground falls below 0°C for two or more consecutive years. Permafrost is widespread in the Northern Hemisphere, but it is extremely rare in Japan and has only been found in a limited number of locations, including the Daisetsu Mountain Range, Mt. Fuji and the Tateyama Mountain Range.

A research group led by Chief Senior Researcher Tokuta Yokohata and Senior Researcher Noriko Ishizaki of the National Institute for Environmental Studies, Overseas Researcher Go Iwahana of the Arctic Research Center, Hokkaido University, and Senior Researcher Kazuyuki Saito of the Japan Agency for Marine-Earth Science and Technology, has estimated the locations where permafrost could exist throughout Japan based on climate information from around 1930 to the present. They found that in addition to the Daisetsu Mountain Range, Mt. Fuji and Tateyama Mountain Range in present-day Japan, there are also potential permafrost sites in the Hidaka Mountains, Mt. Shiretokodake, Mt. Sharidake, Mt. Akandake and Mt. Yotei in Hokkaido, as well as in the Northern and Southern Japan Alps. Moreover, they used the information on future climate projections to predict how areas that could sustain permafrost would change.

The Daisetsu Mountain Range and Mt. Fuji are areas where permafrost areas remain relatively intact because of their higher summit elevations compared to the current lower elevation limit where permafrost can exist, but permafrost areas will decrease significantly in the future regardless of the greenhouse gas emission scenario. While permafrost areas remain in the Hidaka Mountains and the Northern Japan Alps at this time (the first half of 2020), their permafrost areas are projected to disappear within the next 20 to 30 years. Furthermore, Mt. Shiretokodake, Mt. Sharidake, the Southern Japan Alps, Mt. Akandake and Mt. Yotei have been deemed to have already lost their permafrost areas as of 2020.

In their analysis, the group estimated "environments to maintain permafrost" using temperature data for a permafrost area, but this requires some time for changes in the temperature environment to be reflected on the ground. The results of this estimate indicate that permafrost is being lost in these areas or may have already disappeared.

The research group's findings indicate that major changes in the mountain environment, which sustains diverse ecosystems, are inevitable. The group believes that it will be important to monitor mountain environments and study various adaptation measures to climate change. The group's findings were published in Progress in Earth and Planetary Science.