161

Impacts of Global Warming on Alpine Plants Growing
in the Japanese Alpine Zone and Possibility of Monitoring
Global Warming Impacts with Alpine Vegetation
Toshiki NATORI
Physiological Ecology Section, Environmental Biology Division,
National Institute for Environmental Studies
16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japane-mail: tnatori@nies.go.jp

Abstract
This paper introduces the results of our research projects for the Ministry of the Environment anddiscusses the possibility of using alpine vegetation to monitor global warming impacts in Japan. We
plotted the trend of air temperature in the Japanese alpine zone, and then collected information on possible global warming impacts there, some of which we studied in detail. We elucidated the relationships
between these impacts and meteorological factors. From these relationships and common future climate
scenarios, we estimated potential global warming impacts in the Japanese alpine zone. We devised ameasuring system that could operate properly in the alpine zone, where conditions are very severe. The
system operates unmanned, runs on solar power and is small and lightweight. This paper discusses thepossibility of monitoring global warming impacts using alpine vegetation in Japan.
Key words: Alpine plants, flowering time, global warming impacts, monitoring, perennial snow patch

1. Introduction
Global warming due to human activity is anticipated to cause serious problems in the future. In response, the Intergovernmental Panel on Climate
Change (IPCC) was established in 1988. After the
IPCC’s first to third reports came out, reports about
impacts in Japan began to be published (Global Environment Department, 1994; Nishioka & Harasawa,
1997; Global Environment Department, 2001;
Harasawa & Nishioka, 2003). These reports describedsome remarkable impacts on the Japanese alpine zone.
First, global warming during the 20th century wasmuch greater than in any of the previous nine centuries. The best agreement between model simulations
and observations over the last 140 years has beenobtained when all anthropogenic (greenhouse gases
and estimated sulfate aerosols) and natural forcing
factors (solar variation and volcanic activity) are combined. Second, regional changes in climate, particularly increases in temperature, have already affected adiverse set of physical and biological systems in many
parts of the world. Third, the vulnerability of natural
systems to climate change differs across regions. And
fourth, alpine ecosystems are among the most vulnerGlobal Environmental Research
10(2)/2006: 161-166
printed in Japan

able to global warming. Many publications discuss theimpacts of global warming on alpine zones (e.g.,
Nogami, 1994; Beniston, 1994; Omasa et al., 1996;
Masuzawa, 1997; Beniston & Innes, 1998; Köner,2003; Member of the Diet in charge of environment
et al., 2003). On the basis of this information, we
began a research project for the Ministry of theEnvironment. This paper introduces our results anddiscusses the possibility of monitoring global warming impacts using alpine vegetation in Japan. In thisproject I collaborated with members of the School of
Agriculture and Life Sciences at The University ofTokyo, the Faculty of Science at Shizuoka University,and the Hakusan Nature Conservation Center(Ishikawa Prefecture).

2. Air Temperature Changes in the Japanese
Alpine Zone
To study the impacts of global warming on alpine
vegetation in Japan, it is necessary to determine trends
in air temperature in the Japanese alpine zone. We
compared the annual average temperature at the top of
Mt. Fuji (Japan Meteorological Agency, 1967, 1979,
1984 and 2000-2003; Shizuoka Meteorological Obser©2006 AIRIES

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T. NATORI

vatory, 1981-2000) with the global average surface
temperature (Oshima et al., 2003) (Fig. 1). The annual
average temperature at the top of Mt. Fuji has increased since 1980 at a faster rate than the global
average surface temperature. To understand the regional changes in air temperature in the Japanesealpine zone, we compared the annual average temperature at the top of Mt. Fuji with the air temperature
at 3,000 m above Wajima (Ishikawa Pref.) and Tateno(Ibaraki Pref.), and at 1,500 m above Nemuro(Hokkaido). These air temperatures were estimatedfrom aerological data published by the Japan Meteorological Agency (Japan Meteorological Agency, January 1980 - December 2000, 1983) The changes in air
temperature show similar trends (Fig. 2).

Fig. 1 Annual average temperature at the top of Mt. Fuji(●/squares) and global average surface temperature(田/crosses).

Symbols show the moving averages of difference from theannual average temperature from 1961 to 1990. Meteorological
data at the top of Mt. Fuji were published by the Japan
Meteorological Agency. Closed circles show the smoothing
difference of global average surface temperature from theChronological Scientific Environment.

Fig. 2 Comparison of the annual average temperature at the topof Mt. Fuji with upper atmospheric temperatures above
Wajima, Tateno and Nemuro.
Moving average data at the top of Mt. Fuji were calculated
from data published by the Japan Meteorological Agency. Opencircles (○) show the moving average temperature at 3,000 m
above Wajima, open squares (□) at 3,000 m above Tateno, andopen triangles (U) at 1,500 m above Nemuro. These values
were calculated from aerological data published by the Japan
Meteorological Agency.

3. Phenomena Possibly Related to the Increase in Temperature in the Japanese
Alpine Zone
We collected information on phenomena thatmight be related to the increase in temperature in theJapanese alpine zone from the literature and personal
interviews. Examples from the literature have reference; examples with no reference come from personal
interviews. Examples of observed changes include a
decrease in the area of alpine fields by expansion ofsubalpine tree ranges (Mt. Apoi, Hokkaido (Nishikawa
et al., 1993; Watanabe, 2005), Mt. Yatsugatake, Nagano
Pref.), increase in withered needles of Japanese stonepine in early spring at various sites (Haimatsu-kare
Network, 1998a,b), earlier flowering of alpine plants(Mt. Kitadake, Yamanashi Pref (Minamikantochiku
National Park and Wildlife Management Office,1996-2003), Oze, Gunma Pref. (Gunma Prefecture,
1979-2005)), spread of lowland plants such as
Plantago asiatica and lowland animals up into thealpine zone (Mt. Hakusan, Ishikawa Pref. (Nogami,
2001, 2002, 2003)), earlier emergence of alpine
butterflies (Mt. Taisetsu, Hokkaido (Konno & Tanji,
2003)), later molting of Japanese ermine (ShigaKogen, Nagano Pref. (Natori, 2005)), reduction inarea of perennial snow patches (Mt. Hakusan,
Ishikawa Pref. (Ito & Ogawa, 2003)), changes in species composition of alpine vegetation (around Mt.
Tekaridake, Shizuoka Pref.), and reduction in area ofsnow patch vegetation. We selected some of thesechanges to study by field survey and sought any relationships between changes in the phenomena andenvironmental factors such as air temperature andtime of disappearance of snow cover. As examples ofthe earlier flowering of alpine plants, this reportfocuses on changes in the flowering time of
Callianthemum hondense, which grows only in a narrow area on Mt. Kitadake, and Lysichiton camtshatcense, which grows at Oze. As an example of the reduction of perennial snow patches, results of measuring the Senjagaike-Sekkei snow patch are shown.
After we had collected phenological data fromthe alpine zone, we collected data from reports on
the conservation of C. hondense (Minamikantochiku
National Park and Wildlife Management Office,1996-2003) and on conservation at Oze. (Gunma Prefecture, 1979-2005). Because the period of observation of the flowering time of C. hondense in the report
was too short, we added data from a field survey that
I conducted, from flowering specimens preserved at
Tsukuba Botanical Garden, and from Mizuno (1984).
Annual changes in the date of full flowering of
C. hondense and L. camtshatcense are shown respectively in Figs. 3 and 4. Data since 1995 shown in
Fig. 3 (C. hondense) were collected at roughly thesame sites, but data before 1994 contained no detailedsite information. Therefore, strictly speaking, comparisons between data since 1995 and before 1994 areDate of full flowering of C. hondnense(6/1=1)

Impacts of Global Warming on Alpine Plants Growing in the Japanese Alpine Zone

Fig. 3 Annual changes in date of full flowering of
Callianthemum hondense.

Flowering date of L. camtshatcense(5/1=1)

Open circles (○) show dates of full flowering from management reports for the C. hondense conservation area and myfield surveys, and closed circles (●) show data of flowering specimens preserved at Tsukuba Botanical Garden andflowering periods described by Mizuno (1984).

163

not valid, because the date of full flowering of
C. hondense varies among growing sites. Nevertheless,the data suggest that the date of full flowering of
C. hondense has advanced. Data shown in Fig. 4 werecollected at the same site, and suggest that the date offlowering of L. camtshatcense has also advanced. The
relationship between the flowering time of each plantand meteorological factors show that the date of full
flowering of C. hondense was roughly similar to thedate of snow disappearance at the top of Mt. Fuji, andthe date of flowering of L. camtshatcense was related
linearly to the monthly average temperature in April atOze (data not shown).
The Senjagaike-Sekkei snow patch, situated atabout 2,750 m on a western slope of Mt. Hakusan, is
one of the few perennial snow patches in Japan. To
determine the annual change in size of this patch, wemeasured the surface area early in October before
snowfall, when the surface area is minimum. Annualchanges since 1981 in the minimum area are shown in
Fig. 5 with extra data from Dr. F. Ito of Fukui University. During the data period, the maximum area was
4,200 m2 in 1981, and the minimum was 500 m2 in
1998. From 1981 to 1992, the area change tended todecrease, but after 1992 the area showed large variations, though it still showed a tendency to decrease.

4. Evaluation of Risk of Global Warming
Impacts on the Japanese Alpine Zone
Based on Common Future Climate
Scenarios

Fig. 4 Annual changes in dates of flowering of Lysichiton
camtshatcense at Oze.

Area of snow patch (×100m2)

Open circles (○) show dates from a conservation area
report (Gunma Prefecture, 1979-2005).

Fig. 5 Annual changes in size of the Senjagaike-Sekkei
snow patch at Mt. Hakusan.

Symbols ( 田 ) indicate the area early in October before
snowfall. These data came from Mr. Ogawa of the Hakusan
Nature Conservation Center.

We estimated changes in the alpine area in Japan,
flowering time of C. hondense on Mt. Kitadake andL. camtshatcense in Oze, snow patch vegetation, sizeof a perennial snow patch (Senjagaike-Sekkei), andthe growing altitude of P. asiatica at Mt. Hakusan at
10-year intervals from 2000 to 2100 under common
future climate scenarios (mesh size, 10 km × 10 km)
scaled down from General Circulation Models (CCCM,
CSIR, CCSR, MPKI) (Yokozawa et al., 2003) and therelationships estimated in Section 3. We regarded
these changes as indicative of risks of global warming.
Figure 6 shows the impact on flowering time of
C. hondense. The calculation procedure had five steps:(1) A multiple regression equation (dependent variable,
day of snow disappearance at the top of Mt. Fuji;
independent variables, maximum snow depth andmonthly average temperature in May at the top of Mt.
Fuji) was calculated from past meteorological data.
(2) The monthly average temperature in the common
future climate scenarios was corrected to values at the
top of Mt. Fuji. (3) From these corrected values, thefuture maximum snow depth at the top of Mt. Fuji wascalculated according to Inoue and Yokoyama (1998).
(4) Future dates of snow disappearance at the top of
Mt. Fuji were calculated from the multiple regression
equation and from the future maximum snow depth
and future monthly average temperature in May.

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T. NATORI

Fig. 6 Projection of dates of full flowering of
Callianthemum hondense.

Dates of full flowering were calculated for intervals of 10
years from 2000 to 2100 under common future climatechange scenarios and from the relationship between
meteorological factors and dates of full flowering of
C. hondense.

(5) From the relationship described in Section 3, thefuture date of snow disappearance at the top of Mt.
Fuji was regarded as the future date of full floweringof C. hondense. This date was shown to gradually
become earlier, falling to the beginning of June by the2040s in the average of four common future climate
scenarios. This date was also the earliest date of full
flowering during our research period, in 1998.

5. Establishing a System for Measuring
Snow Factors in the Japanese Alpine
Zone
To evaluate the impacts of global warming in alpine zones, it is necessary to determine the relationships between changes in the alpine zones and meteorological factors. The main meteorological characteristics of the Japanese alpine zone are strong wind andheavy snowfall in winter in spite of the low altitude.
Many phenomena in the Japanese alpine zone are influenced strongly not only by low temperatures, butalso by snow factors such as the time of snow disappearance and snow depth. The limited meteorological data published allow air temperature at various
sites in the Japanese alpine zone to be estimated, but
the time of snow disappearance and snow depth are
difficult to estimate, because they are influenced
strongly by micro-topography. Therefore, to measuresnow factors in the Japanese alpine zone, where conditions are severe, requires a small, lightweight, automatic measuring system that can withstand the conditions. We tested three such systems.
The first was a commercial field thermometer with
two sensors set at different heights, powered by a lithium battery. The sensors recorded the temperature
every hour from the beginning of November to thefollowing June or July. The records allowed us to esti-

mate the date of snow disappearance more clearly
than the records of thermometers with one sensor. The
second was a commercial half-film camera that took
one picture every day from the beginning of thesnow-melt season. From the 72 half-photographs, we
could calculate the day of snow disappearance. We
made the third from a digital camera that operated
automatically, because of the inaccessibility in winterof observation sites that we could reach at beginningof the snow melt season. With a 1-gigabyte memory
card and two solar panels, this camera operated every
day for a year. It recorded not only the date of snow
disappearance, but also the date of flowering of alpine
plants.
We also tested a small, lightweight snow pressuregauge to estimate snow depth and an anemometer. In
addition, using the Normalized Difference Vegetation
Index (NDVI ) calculated from NOAA data, we havebeen developing the method to estimate the disappearance of snow in the Japanese alpine zone in past years.

6. Discussion
To determine the vulnerability of the Japanese alpine ecosystem to global warming, we focused on thesmall number of meteorological factors that are recorded widely throughout the Japanese alpine zone
and monthly meteorological data from common futureclimate scenarios. To project the date of full floweringof C. hondense we used the maximum snow depth,
calculated from the monthly average temperature andmonthly precipitation, and the monthly average temperature in May. To project the distribution of alpine
vegetation warmth indices, we used the monthly average temperature, although there is criticism that therelationship between the warmth index and distribution range of alpine vegetation in Japan is too static(Uchijima, 1993). From these results and the results
obtained in Sections 3 and 4, we concluded that theJapanese alpine ecosystem is vulnerable to global
warming. Therefore, the impacts on the ecosystem are
not unique, because the relationships between the phenomena and meteorological factors are not unique.
Thus, it is necessary to investigate these relationships
in detail and clarify the impacts of rising temperatureon the Japanese alpine ecosystem. Furthermore, therelationships between rising temperature and othermeteorological factors must be considered together,because increasing temperature is linked with drought
and changes in rainfall; for example, the potential
evapotranspiration as a simple index of climate(Iwasaki, 1974) is calculated from the monthly average temperature and rainfall. It will also be necessary
to establish methods of measuring other meteorological factors in the Japanese alpine zone.
Given the above results, is it possible to monitor
global warming impacts from the alpine vegetation in
Japan? The Japanese alpine zone has four distinct seasons with characteristic temperatures. Therefore, anImpacts of Global Warming on Alpine Plants Growing in the Japanese Alpine Zone

increase in temperature caused by global warming will
have effects on almost all natural phenomena in thezone. Relating particular phenomena to global warming, however, is not straightforward. Nevertheless, thethird report from the IPCC concluded that regionalchanges in climate, particularly increases in temperature, have already affected a diverse set of physicaland biological systems in many parts of the world.
Many people support this conclusion, which is basedon the following evidence: the degree of warming
during the 20th century was much greater than during
the previous nine centuries; the best agreement between model simulations and observations over thelast 140 years has been found when all anthropogenic
and natural forcing factors are combined; long-termchanges, typically of 20 years or more, in biologicaland physical systems are correlated with regionalchanges in temperature; the relationships betweenchanges in biological and physical systems and increases in temperature are scientifically clear, and the
direction of changes is explained by known mechanisms; and changes in these systems are consistentand coherent across diverse regions. Thus, it can beconcluded that recent regional changes in temperature
have had discernible impacts on many physical andbiological systems (Global Environment Departmnet,
2001).
In Japan, the change in annual average temperature
at the top of Mt. Fuji has increased since 1980 in stepwith the global average surface temperature (Fig. 1),
and these increases are similar to those in the Japanesealpine zone (Fig. 2). Several observed long-termchanges in biological phenomena and the relationships
between them and temperature change are relatively
clear. The size of Senjagaike-Sekkei, a perennial snow
patch at Mt. Hakusan, has tended to decrease since1981. And the flowering times of C. hondense andL. camtshatcense appear to have advanced recently. It
will be necessary to study changes over the long term,
including those clearly related to change in temperature, throughout the Japanese alpine zone. Data should
be collected at fixed sites because phenomena arelocally affected by snow factors.
Decreases in the size of alpine fields on Mt. Apoi
due to expansion of the distribution range of subalpine
trees have recently been recognized. Similar projectedchanges in the distribution of vegetation caused by
global warming are well described in the literature.
However, the relationship between the range of vegetation distrubution and temperature is complex. For
example, the range of the Japanese stone pine wasrelated to warmth index in one study (Ohmori &Yanagimachi, 1989) and not related in another (Okitsu& Ito, 1984). In an analysis of the relationship between change in vegetation distribution and climatechange, the time scale and reaction time (or time constant) are very important, and the response time tends
to increase with an increase in complexity from theindividual to the ecosystem level (Uchijima, 1993). As

165

Uchijima (1993) pointed out, we must clarify the dynamic relationships between the distribution ofvegetation selected as a biological index of global
warming and climate change. In this way, changes inthe distribution of vegetation can be used as an index
of global warming.
In the Japanese alpine zone, other biologicalchanges could be developed as biological indices, including the molting time of the Japanese ermine,
withering of needles of the Japanese stone pine inearly spring, and changes in species compositions ofalpine vegetation. If the relationships between thesechanges and the increase in temperature can beclarified, these changes could be useful indices ofglobal warming.

Acknowledgments
I acknowledge the kindness of Dr. Y. Kadota forlooking for the flowering specimens preserved at
Tsukuba Botanical Garden. I also thank Mr. H.
Shiozawa and Mr. K. Inomata for their advice on thefield survey at Mt. Kitadake.
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(Received 15 June 2006, Accepted 26 September 2006)