Oze National Park
guide bookContents
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Introducing Oze
Column/The Origins of Oze National ParkThe Four Seasons of Oze
How Oze Evolved/All About the Oze Marshland
Column/Oze and the Ramsar Convention
Plant Life of Oze

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P. 11
P. 12
P. 14

Animals of Oze
Column/Bear Encounter Tips
Oze History of Conservation
A Hiking Guide to Oze/Ozeʼs Mountain Lodges
Suggested Hiking Courses

Gunma PrefectureIntroducing Oze
Oze is the familiarname for the expansive
area of mountains andmarshland that makes
up Oze National Park. It
is located in the centerof Japanʼs largest islandof Honshu, and straddles
four prefectures: Gunma,
Fukushima, Niigata, andTochigi.
Oze
Gunma
Ozeʼs natural environmentshows little sign ofhuman interference.
Tokyo
Thanks to some ofJapanʼs strongest
environmental protection
programs, the areaʼs
topography and wildlife
h a ve r e t a i n e d m a n yphysical and ecologicalcharacteristics that have developed over the millennia.
The marshlands of Oze, which are one Japanʼs largest high moors, cover two basins, thewestern Ozegahara marsh and the Lake Ozenuma area to the east. The Ozegahara marsh
covers an area 6 kilometers long and 2 kilometers wide, where the average altitude is 1,400
meters. Lake Ozenuma, which lies at an altitude of 1,660 meters, has a circumference of 9
kilometers. The plateau was formed after lava from volcanic eruptions some two million years
ago created an independent depression. This gradually evolved into the peat moor that is now
home to expansive ﬁelds of marsh plants, including a variety of colorful wildﬂowers.
The Ozegahara marsh is surrounded by mountains in the 2,000-meter range, with the highest,
Mt. Hiuchi, reaching 2,356 meters. All but the peak of Mt. Shibutsu are volcanic in origin andcovered in thick forest. Mt. Shibutsuʼs mineral makeup is less compatible with plant growth,
so it has a lower tree line than the other peaks, giving hikers panoramic views of the marshes
spreading out to the east.
There are no roads in the national park. The only entrances to the park are forest trails fromseveral mountain passes that lead up to the surrounding mountain peaks or down to themarsh area. The Hatomachi-toge Pass on the Gunma Prefecture side of the park is the mostpopular entrance. The hiking trails in the mountains are clearly marked and well maintained,
as are the protective boardwalks that crisscross the marshland. The routes are varied, fromcourses that can be covered on a day trip to longer routes that require staying overnight in
the park.
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Oze National Park is open from early May to late October. Even over this relatively shortseason, Oze shows many different faces, as the altitude and weather patterns result inconstantly changing conditions. Watching the early morning fog over the peat moors slowly
lift to reveal the silhouette of the surrounding mountains is an unforgettable experience.
Rainbows occur often, and sunny days can quickly turn cloudy, and vice versa. Many visitors
are enthusiastic photographers, who come to capture Oze in its many manifestations.
The park is closed in the winter due to massive amounts of snow and bitter cold temperaturesthat reach as low as -10°C. Because of the high altitude, summer temperatures rarely reach 30°C,
and nights can become quite chilly.
There are two Visitor Centers where knowledgeable staﬀ are on hand to help guests learn
about the park, its natural environment, animal life, and other characteristics. They can also
help with practical and logistical advice about the mountain trails, boardwalk routes, andrecommended clothing and equipment. There are three campsites and over 20 lodges aroundthe park, oﬀering accommodation, meals, and hot baths for hikers.
For many years, Oze has been the focus of preservation efforts by conservation activists,
mountain lodge operators, park administrators, and, of course, visitors. The national park
continues to protect the environment while sharing its natural beauty with visitors.

The View from the top of Mt.shibutsu

The Origins of Oze National ParkThe Oze area was included in Nikko National Park in 1934, becoming part of Japanʼsfourth national park. However, the two areas are very diﬀerent environmentally, so Oze
National Park was established as an independent entity in August 2007. It expanded
to include areas around Mt. Aizukoma and Mt. Tashiro, becoming Japanʼs twenty-ninth
national park. Only 150 kilometers from Tokyo and right on the border of the Kanto andTohoku regions, Oze is a popular destination for day visitors, campers, and hikers.
Oze National Park has long been at the forefront of conservation in Japan, thanks topublic-led efforts that stopped the construction of electric power generation plantsthat would have flooded much of the area. Other initiatives included blocking roaddevelopment into the park and launching programs against littering and other potential
damage from tourism.
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The Four Seasons of Oze
The seasons in Oze are distinct, and many repeat visitors come at diﬀerent times of the year
in order to experience its seasonal highlights.

SpringSpring comes late in Oze, with thesnow beginning to melt in early
M a y. T h e Vi s i t o r C e n t e r s b e g i n
operations, and the mountain huts
are dug out from under the snow
and start accepting visitors. Late
May to mid-June is the season of themizubasho, or Asian skunk cabbage,
which brightens the marshes with its
white flowers, attracting large
numbers of visitors. Later,
marsh marigolds add their
golden yellow hues to thelandscape.
Mizubasho Asian skunk
cabbageMarsh-marigold

Summer
The summer season is when themountains are most accessible andthe basins most verdant. In July themarshes turn white with the fluff ofcottonsedge (eriophorum ), then shift
to bright yellow when the day lilies
bloom later in the month. This is
the peak of Ozeʼs floral (and tourist)
season. Hikers come to climb the
many peaks and casual visitors cometo enjoy the scenery from theboardwalks that traverse
the marshes.

Day lilie

Cottonsedge

4Autumn
The climate turns cooler in late August
as autumn comes to Oze, and animals
begin preparing for a long winterhibernation. The foliage begins tochange color in September, when themarsh grasses and other vegetation
turn to autumn gold. Later in themonth, trees on the mountainsides
like maple and beech turn bright red,
yellow and brown. Snow begins
t o f a l l i n O c t o b e r, a n d b y
November has accumulated
into deep drifts, making thepark largely inaccessible until
spring.
Ezo rindo

Winter
The snowfalls that begin in midOctober eventually turn all of Oze
into deep snow country. The park
staff and mountain huts prepare thefacilities to survive the elements, thenleave for the winter period. The snow
layer, which can reach depths of 3 to
4 meters in parts of the park, plays
a big part in maintaining the Ozeʼsecosystem, protecting the plants fromthe bitter winds of mid-winter andnourishing the growth of new sprouts
as snowmelt in late spring.

5How Oze Evolved
The entire Oze area was a plateau until
about two million years ago, when
Mt.Shibutsu
Mt. Shibutsu began forming fromserpentine rock on the western edgeof a shallow valley. Volcanic eruptions
began to form other mountains nearby.
The lava flow from these mountains
was of low viscosity, creating broadand shallow shield-volcano formations,so called because they look like awarriorʼs shield laid on the ground
Mt.Hiuchi
face-up. As mountains surrounded the
Mt.Keizuru
central plateau, Ozeʼs landscape began
Mt.Shibutsu
to take on its present conﬁguration.
Lake
Ozegahara Marsh Ozenuma
Mt. Hiuchi was the last mountain in thearea to erupt, beginning about 350,000
Ayamedaira Marshyears ago, during the Pleistocene
epoch. The lava ﬂow from its western
slope changed the ﬂow of existing rivers. Lake Ozenuma was formed around 10,000 years
ago, when lava ﬂow on the southern side, possibly aided by erosion from the mountain slopes,
blocked the ﬂow of the Nushiri River.
In later times, streams and rivers ﬂowing down from the mountains deposited silt and otherresidue in the area now known as the Ozegahara marsh. The rivers frequently flooded orchanged course, creating small, independent bog pools and wetlands where plants began todecompose, eventually creating the thick surface of peat that covers the plateau today.

All About the Oze Marshland
Peat forms when conditions such as cold temperaturesand excessive humidity prevent dead vegetation from fully
decomposing, leaving behind a greater amount of organic
material. Oze has an average annual temperature of 4 °C,
about the same as the inside of a refrigerator, easily coldenough to inhibit the decaying process.
The partly decayed material builds up and condenses overmany thousands of years, eventually turning into peat soil.
Peat
The rate of peat growth in Oze is approximately 0.7 ‒ 0.8
mm a year, although this can vary depending on the plants and the climate. If a hiker wereto step oﬀ the boardwalk and make a 1-centimeter depression in the peat, it would take ten
years for the marsh to recover. Researchers believe that it took 6,000 to 8,000 years for themoorʼs peat surface to reach its present thickness of 5 meters.

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The plants that cover the Ozegahara
marsh vary depending on the makeupof the vegetation under the surface and
Bank
Bank
how the habitat was formed. There areover 1,800 bog pools, ranging from 2
River
Peat
Peat
to over 100 meters in diameter, withdepths from around 10 centimeters toover 3 meters.
Most of the marshes of Ozegahara are the result of repeatedﬂooding. Each time the rivers retreated, they left wetlands
on both sides, separated by high banks. (See illustration.)
These wetlands are an ideal habitat for reeds, grass-likesedges, and plants such as bogbean (Menyanthes trifoliata ).
As these plants partially decompose, they form peat, ﬁllingin depressions and creating a ﬂat surface.
①②③

low moorbog poolearth and sandearth and sand

Peat

Peat

The marshes near Lake Ozenuma developed diﬀerently, starting as bog pools that gradually
filled with earth and sand as their banks eroded. This created a thriving environment foraquatic plants that also turned into peat as they decomposed. This type ofmarsh is called a “low moor,” as the surface is usually at the same level
as the surrounding water table. The peat receives nourishment fromthe river water, which is vital to the ﬁelds of mizubasho (Asian skunk
cabbage ) that grow here.
bogbeanOze and the Ramsar Convention
In November 2005, Oze was registered as a Ramsar Convention site, in recognition of
its importance as a wetland habitat for migratory birds. The convention, named after
the Iranian city where it was signed in 1971, is aninternational treaty for the conservation and sustainable
use of wetlands, and covers rivers, lakes, paddies,
reservoirs, sea coves, tidal ﬂats, and mangrove forests. As
of December 2019, there are 52 Ramsar sites in Japanand over 2,000 in the 170 countries that signed theagreement.

7Plant Life of Oze
The areaʼs distinct topography, geography, and climate conditions have created several
ecosystems that host over 900 plant species. Oze lies at the intersection of four distinct typesof vegetation: Northern, Southern, Paciﬁc, and Japan Sea varieties.
Mountain Forests
The mountains surrounding Ozegahara are largely
covered with deciduous trees, which vary depending on
the altitude and the kind of soil. Japanese beech trees(Fagus crenata ), with their oﬀ-white bark, are numerous
in the Hatomachi-toge Pass area, for example, while
the trail down to Yamanohana passes through forestsof Japanese oak (Quercus crispula ). At altitudes over
1,600 meters, coniferous trees such as Maries ﬁr (Abies
mariesii ) and spruce (Picea jezoensis subsp. hondoensis )are more plentiful.
Very little light reaches the forest floor, and visitors with a keen eye may spot ginryoso(Monotropastrum humile ), a plant with small white flowers that does not perform
photosynthesis like other plants, instead getting its nutrients from fungi.
Mt. Shibutsu is not volcanic but largely made up of serpentinite, so named because of its
snakeskin-like appearance. Due to the high magnesium and iron content of the rock, it is
not conducive to the growth of many varieties of plants. One plant that manages to growon Mt. Shibutsu is ozeso(Japonolirion osense ), whichtakes its name from Oze. This,
along with Arenaria katoana
and Leontopodium fauriei var.
angustifolium (see photos), arerecognized as serpentinitepersistent plants.
ginryoso

Leontopadium fauriei
var. angustifolium

Ozeso

Marsh Plants
During the spring and summer months the marshes are carpeted with ﬂowers. Mizubasho, or
Asian skunk cabbage (Lysichiton camtschatcense ) is the ﬁrst to make its appearance, covering
many parts of the marshes in white from late May to mid-June. What looks like a white
blossom, however, is actually a leaf called a spathe. The bright yellow-orange daylily called
Nikko kisuge (Hemerocallis esculenta ) is also a perennial favorite for visitors, appearing in
mid-July. As the English name implies, the ﬂowers only bloom for one day. Delicate blossoms
appear on the stems of the iwashobu (Triantha japonica ), an alpine plant that is thought todate back to the Ice Age.
Other plants frequently seen in Oze include the spongy mizugoke (bog moss ) that holds a lotof water, and cottonsedge (Eriophorum vaginatum )known as watasuge.
The pygmy water lily, or hitsujigusa (Nymphaea
tetragona ), is among the plants growing in the ponds
and small lakes, along with Ozekohone (Nuphar
pumilum var. ozeense ), which has leaves like a lotus,
but with yellow blossoms.
hitsujigusa
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OzekohoneAnimals of Oze
Oze is home to animal life as diverse as the range of habitats in the park, from the smallest
dragonfly in Japan, with a body only 2 centimeters long and wing length of only 15
millimeters, to the Asian black bear, which can weigh up to 200 kilograms.
These animals play an important part in the areaʼs ecology. For example, thanks to the seeds
in their droppings, bears help plants grow over a large area. Research is being conducted on
ways to keep visitors from encroaching on the bearsʼ habitats.
Recent changes in climate have caused an increase in the number of deer in the park,
something previously unheard of. The growing deer population can damage the marshes andchange the ecology of the forests, so strategies for limiting their numbers are being studied.
Mammals
There are 34 species of mammals in the park, although most are rarely seen by visitors.
The Asian black bear (Ursus thibetanus ), is medium sized and largely herbivorous (seebelow for what to do in case of a bear encounter). The Japanese serow (Capricornis crispus ) is akind of goat-antelope, an even-toed bovine. One favorite animal, though rarely spotted, is theJapanese stoat (okojo; Mustela erminea Nippon ). While it appears adorable and harmless, it isa carnivorous hunter of small mammals and birds. Other mammals sometimes spotted include
rabbits and the tiny Japanese dormouse.

Asian black bear

Japanese serow

Bear Encounter Tips
Asian black bears are less aggressive than many
species of bears and tend to avoid humans. They
can be dangerous if they feel threatened or arecaught by surprise. Visitors are encouraged to ring
the bells that are placed in certain areas along theboardwalks, and to let bears know humans are nearby clapping or talking. If you encounter a bear, do
not make loud noises or run, but slowly and quietly
exit the area.
Bell

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Japanese StoatBirdsOver 160 bird species have been reported in the park. Many
migratory birds prefer the marshlands, while others make theirhome in the forests. The chestnut-eared bunting (Emberiza fucata ),Indian spot-billed duck (Anas poecilorhyncha ), and Lathamʼs snipe(Gallinago hardwickii ) can be spotted in the marshes. The forests
shelter the Great spotted woodpecker (Dendrocopos major ), thenarcissus flycatcher (Ficedula narcissina ), and the bush warbler(Horornis diphone ), once called the Japanese nightingale for the
Chestnut-eared bunting
beauty of its song. The alpine accentor (Prunella collaris ) andthe spotted nutcracker (Nucifraga caryocatactes ) can be found in rocky areas at the higher
altitudes.

Montane brown frog

Japanese Pire bellynewt

Amphibians
Nine species of amphibians live in thepark, including the Montane brown frog
(Rana ornativentris ), which is endemic toJapan, and the Japanese fire belly newt
(Cynops pyrrhogaster ), often spottedfrom the boardwalks over the ponds andrivers. Others, like the Tohoku salamander(Hynobius lichenatus ), are more diﬃcult to
spot.

Fish
Ten species of fish, including thetrout-like iwana (Salvelinus ), andthe tiny Amur minnow, live in Oze.
Though grilled iwana is a favorite
local dish, ﬁshing is not allowed in
the park.

iwana(Salvelinus)

Insects
Ozeʼs ecosystems are ideal for insects, and a wide variety can befound throughout the ponds, rivers, marshlands, and forests of thepark. These include dragonflies that only inhabit cold areas andbutterﬂies that prefer high altitudes. Among them are the damselﬂy(Zygoptera ), the scarlet dwarf or pygmy dragonfly (Nannophyapygmaea ), and the Old World swallowtail butterfly (Papilio
machaon ).
pygmy dragonﬂy
10Oze History of ConservationOze has been a pioneer in nature conservation since early visitors fell in love with thelandscape and determined to protect it.
During the Edo period (1603‒1868), the area wasoften visited by hunters and fishermen, drawn to thegame attracted by the lush marshes. The Aizu-Numataroad, a mountain route used to carry food and othergoods between the district to the north (Aizu) andthe southern district (Joshu), passed across the Oze
area. By the end of the Meiji era (1868‒1912), thefirst mountain lodge was built, and Ozeʼs topography
became the subject of research and nature studies.
The Oze area was first targeted for development in1903 as part of a plan to construct a system of dams
and tunnels that would supply hydroelectric power to aswiftly modernizing Japan. Luckily, nature enthusiasts
were able to organize and stop the plan. Their activism
became more focused with the establishment of the Oze
Conservation Association in 1949.
The boardwalks is constructed manually

The most recognizable symbols of Ozeʼs conservation
approach are the boardwalks that protect the fragile surface of the national parkʼs marshlands.
In the beginning they were just logs laid across spots that were diﬃcult to cross; later the logs
were split and laid ﬂat, making walking around the marshes even easier. By the 1950s, thedamage from increasing numbers of visitors had become apparent, and serious work on theboardwalk system began in 1952. These boardwalks, most of them raised above the surfaceof the marsh, now extend over 54 kilometers.
Oze was once slated for road development, but this, too, was blocked by environmental
activists. When trash left by climbers and hikers began to overwhelm the area, Oze began acampaign to get visitors to take their waste home with them. The campaign was successful,and the movement spread to other areas around Japan dealing with the same issue.
M o s t r e c e n t l y, O z e h a s e s t a b l i s h e dprograms aimed at maintaining the areaʼswater quality and promoting the use ofclean energy, such as solar power. Throughthe efforts of park staff and volunteers,
and with the cooperation of visitors, Oze
will continue to protect the parkʼs natural
resources.

The trash left byclimbers and hikers
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A campaign to get visitors totake their waste home with them

A Hiking Guide to Oze
Oze has well-maintained hiking courses for every class of hiker, from the level boardwalks thatcrisscross the marshlands to steep mountain trails that reach high above the tree line. Hikers
should keep in mind that the weather can be very unpredictable, due to the ring of surrounding
mountains. A perfectly clear, warm morning can turn misty and cold by afternoon, and viceversa. Visitors are encouraged to wear appropriate clothing that is comfortable, and bring rain
gear and extra layers.
WHAT TO WEAR
Hat
Solar rays are strong at high altitudes, so a hat with a brim is recommended.
Underwear or base layer
Light synthetic or wool fabric that will dry quickly.
Long-sleeved shirt
Quick-drying materials recommended.
Socks and shoes
Thick socks and comfortable yet sturdy walking shoes. For
mountain trails, high-cut hiking boots.
Backpack
Size depends on length of hike and tent use. A rain cover isrecommended.
Hiking pantsLightweight synthetic, long pants, or shorts over tights.
WHAT TO CARRY
Warm layer (ﬂeece, down, or synthetic fabric shirt)
Waterproof jacket and pants
Drinking water
Garbage bag

Ozeʼs Mountain Lodges
There are over 20 mountain lodges (yamagoya ) in Oze National Park, oﬀering accommodation
for hikers with two full meals and hot baths. Visitors should be aware that meals are served early,
because Japanese hikers tend to arrive by mid-afternoon and make early starts in the morning.
Breakfast is usually served at 6:00 A.M., with the evening meal at 5:00 or 5:30 P.M. These lodges
have been operated by the same families
for generations and the staff are founts ofknowledge about Ozeʼs history, nature, and otheraspects of the park. They help maintain the trails
as well and can update visitors on hiking andweather conditions. All the lodges follow strong
conservation protocols, including toilet systems
that do not pollute the water table. Guests are
asked to cooperate with these eﬀorts, including
carrying out any garbage they brought in.

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Staying at one of the lodges for a nightor two gives hikers a deeper experienceand appreciation for Ozeʼs wild naturalenvironment. During golden hour, the early
evening sun bathes the area in a warm light,
and the air cools quickly after sunset. With
little light pollution, Oze is one of Japanʼsbest sites for viewing the night sky. Early
risers can enjoy the fog banks that cover
the marshes, slowly rising to unveil themountains around the plateau.
Note that the lodges can get crowded,
particularly in peak seasons, so reservations
should be made well in advance.

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Suggested Hiking Courses
Hikers can plan their own routes using the trails that crisscross thepark, through marshes and mountain forests. These are two sample
courses, a one-day hike around the marshes, and a two-day hike that
includes climbing Mt. Shibutsu.
Sample Course 1
Woodland Wonders and High-altitude Marshlands

A beginner-friendly descent through mountain forests to themarsh plateau and back, oﬀering splendid views of the valley
Route： Hatomachi-toge Pass ‒ Yamanohana ‒ Ryugu-jujiro Crossroad‒ Yoppi Suspension Bridge ‒ Hatomachi-toge Pass
Total time：6 hours
Level：Easy
Details
This hike is mostly downhill or over flat boardwalks, except for theﬁnal ascent back up to the parkʼs entrance. The ﬁrst hour is a descentto Yamanohana, where hikers will ﬁnd a Visitor Center, lodges, and acampsite. From there, the trail leads across the broad, open expanse of
the marshes, with great views of the surrounding mountains, ponds,
and seasonal marsh flowers. Every so often, there are rest areas,
wooden platforms with benches where people may eat or rest theirlegs. This course follows a circular route around the marshes, but canbe shortened by turning back at the Ryugu-jujiro crossroad.
Sample Course 2
Up the Serpentinite Trail

For experienced hikers, this two-day course features a steep
ascent of Mt. Shibutsu, for panoramic views in all directions.
Route: Hatomachi-toge Pass ‒ Yamanohana ‒ Marsh walks ‒ Mt.
Shibutsu ‒ Hatomachi-toge Pass
Total time: 2 days (6 hours per day)Level: Easy (Day 1); Hard (Day 2)
The ﬁrst day follows the same itinerary as the ﬁrst sample course. Be
sure to reserve accommodation at one of the lodges in Yamanohanaor the Ryugu-jujiro crossroad. On the second day, get up early andtake the trailhead at Yamanohana. The trail climbs steeply through theforest before rising above the tree line. Note that the serpentinite rockunderfoot can be very slippery, particularly when wet, and the wind canbe strong. From Mt. Shibutsu, hikers will get open views of the marshes
on the plateau and the volcanic mountains surrounding the area. The
descent follows the ridge route down to Hatomachi-toge Pass.
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協力：尾瀬保護財団

C

ho

ei

-s h i n d oTrai l15

How You can Help
All visitors can contribute to preserving Ozeʼs natural environment.
Stay on the Paths
The boardwalks and hiking paths have been built to protect the parkʼs wildlife and naturalenvironment from damage. Hundreds of thousands of visitors come to Oze each year, and weneed everyoneʼs cooperation.
Take Everything You Bring to the Park Home with You
A single piece of litter can aﬀect the parkʼs fragile environment. Take all the pictures you want
but be sure to leave the park with all your garbage.
Water Quality Is Everyoneʼs Business
Water is a precious resource in Oze. Donʼt use soap or shampoo at the campsites or in themountain hutʼs baths.
Think of Others
Oze is a place to get back to nature. Let others experience the natural sights and sounds
without disturbances.
If You Need Help . . .
The staﬀ at the Visitor Centers can answer questions and provide information to park guests.
Feel free to drop by and share your feedback.

Information
Oze-Yamanohana Visitor Center
Activities in and around Ozegahara Marsh/Mt. Shibutsu and a source of information The OzeYamanohana Visitor Center is located at
the access point to Ozegahara Marsh. The
Foundation staﬀ stationed at the center provide
information on Ozeʼs natural environment. Daily
nature information collected by staﬀ is posted
at the center, so feel free to drop by before
exploring the area.
Opening hours
7:00 ‒ 18:00
Staﬀ-stationed hours
7:30 ‒ 16:00

Gunma Prefectural Government
Natural Environment Division
1-1-1 Ote-machi, Maebashi-shi
Gunma 371-8570 JAPAN
Phone: +81-27-226-2881
Fax: +81-27-220-4421
16This English-language text was created by the Japan Tourism Agency.

2020.3̲1,000