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Mount Fuji looms over Lake Kawaguchi, about 100km west of Tokyo. Photo: EPA-EFE

When green isn’t good: Mount Fuji’s reforestation linked to global warming

  • Study finds tree line has climbed up slope 30 metres and temperatures at peak have increased 2 degrees Celsius over several decades
  • Scientists attributed the change to climate change, warning about the implications for Japan’s flora and fauna
Greenery is inching up the previously grey and barren slopes of Japan’s Mount Fuji, with experts linking the gradual reforestation of the nation’s most iconic peak to global warming.

A study by Japanese scientists and published in the scientific journal Plants indicates that the tree line on Mount Fuji has climbed up the slope by as much as 30 metres in the last four decades. It also points out that larch trees that typically grow close to the ground and follow the contours of the windswept 3,776-metre peak are increasingly standing upright.

The scientific findings tally with the unseasonably late appearance of snow on the upper levels of the mountain, which stands about 100km west of Tokyo. Even in late December, observers were remarking that there was still no snow at the top of the peak – a sign that some took to mean that magma was rising within the volcano and that an eruption was possible.

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A more likely explanation is that while parts of northern Japan are experiencing record snowfall this winter, temperatures in much of the rest of the country are above average and climate change is having an impact on Japanese flora and fauna.
The academic study, conducted by scientists from Niigata University’s Sado Island Centre for Ecological Sustainability and the biology department at Shizuoka University, concludes that in the 40 years from 1978, the timberline on Mount Fuji “advanced rapidly upwards and the degree of vegetation cover above the timberline increased remarkably”.

Temperatures at the timberline are at a high of 11.8 degrees Celsius (53 degrees Fahrenheit) in August and minus 9.5 degrees Celsius in February, the study found, with snow typically piling up to a depth of 30cm at the height of winter. Other studies have determined that the maximum temperature at the peak of Mount Fuji between June and September has risen by about 2 degrees Celsius in the last 50 years.

An aerial view of Mount Fuji. Photo: Neil Newman

The research focused on the foliage that is gaining a new hold on a stretch of the mountainside in the southeastern flank of the volcano at an altitude of 2,400 metres above sea level.

The team, headed by Hitoshi Sakio, a professor of forest ecology at Niigata University, gathered data on the number of trees in the target area, monitored their rate of growth and how their shapes altered over time. The trees on the mountain were primarily larch and over the four decades of the study both increased in number and were found up to 30 metres higher up the slope.

The findings of the report do not indicate that the entire mountain is likely to get a green coating at any point in the near future, but experts agree that the study underlines the impact of global warming on Japan’s geography.

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“We know that as the earth’s climate changes that vegetation migrates to more northerly latitudes and higher altitudes on mountains,” said Kevin Short, a professor who specialises in environmental education at the Tokyo University of Information Sciences.

“But this does seem to be quite a rapid increase in altitude for this sort of vegetation,” he told This Week in Asia. “But now we are witnessing it, I see no reason why it will not continue, on Mount Fuji as well as Japan’s other mountains. We are already seeing a general retreat in the indigenous ‘buna’ [beech] forest and the advance of broad-leaf evergreens in its place.”

As elsewhere, climate change has impacted the Japanese archipelago, although the pace of change has been unusually fast and dramatic in the last 100 years, Short said, with serious implications for flora and fauna, particularly in coastal regions.

“In the past, flora and fauna have had time to adjust to the new conditions, but what is happening now is just so rapid that ecosystems do not have the time to adjust and that is causing a serious loss of biodiversity,” he said.


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“And for an island nation, the biggest issue has to be rising sea levels rather than what is happening in the mountains,” he added. “If sea levels keep rising, that of course represents a major threat to Japan because the vast majority of the nation’s population is heavily concentrated in the low-lying coastal areas and around the major cities of Tokyo and Osaka.

“Even now, large areas of the coastal plains are below sea level and are only kept from flooding by the excellent networks of dykes,” he said.

“In the future, rising sea levels combined with more powerful typhoons and the possibility of high tides could see those dykes broached, and that is why it is important that we continue to monitor the changes that climate change is having on both the rural and urban environments.”