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Forests on Mt. Fuji creeping to higher altitude amid global warming: study

A snow-capped Mount Fuji is seen, with its lowest regions of snow coverage demarcating the tree line, in this image provided by professor Hitoshi Sakio of Niigata University.
The edge of the forest on Mount Fuji is seen marked by a line in the center of this partially modified image provided by professor Hitoshi Sakio of Niigata University.

NIIGATA -- The edges of the forest on Mount Fuji have crept up several dozen meters in altitude over the past 40 years, an ecological study has found.

    The findings, which have been attributed to global warming, emerged in a study led by forest ecology professor Hitoshi Sakio, who heads the Sado Island Center for Ecological Sustainability at Niigata University.

    Although it appears Mount Fuji's renowned snowy scenes are not under threat, the team said the results showed first and foremost the effect global warming is having on ecosystems.

    The border of Mount Fuji's winter snow scenery that separates its peak from the forest below is known as the "tree line" or "forest limit" -- the edge of the habitat at which trees can grow. Such limits are found at high altitudes as well as in polar regions.

    The research team made fixed-point observations of the tree line some 2,400 meters up Mount Fuji's southwest slope, in the central Japan prefecture of Shizuoka between 1978 and 2018. In that period, Salix reinii willow trees advanced some 40 meters further up, while tall Japanese larches climbed 30 meters higher. It was also confirmed that the increase in individual trees had accelerated over the last two decades compared to the first 20 years during the period.

    When observing the shape of the Japanese larches, researchers found that while in 1978 the branches had spread out wide into a kind of table formation, the number of individual trees growing upright had increased by 2018. The team says this is evidence the branches have become able to develop upwards without dying.

    Average temperatures and concentrations of carbon dioxide necessary for photosynthesis continued to rise on Mount Fuji during the period. The research team accordingly attributes the rise in the mountain's forest limit to the effects of global warming.

    Professor Sakio commented that the tree line had "risen very quickly considering the harsh environment." He added that if warming continues, it's "possible that Japanese larches and other greenery will no longer be able to exist there, and that they will be replaced by other plants."

    (Japanese original by Yui Shuzo, Niigata Bureau)

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