Directory of Protected Areas in East Asia - IUCN

Directory of Protected Areas in East Asia: People, Organisations and Places
Name Latitude/Longitude Area (ha)
Date of
inscription
Biwa-ko 35°15’N/136°05’E 65,602 1993
Principal features: The world’s third oldest lake, Biwa-ko is the country’s largest. The watershed approximates
the administrative borders of Shiga Prefecture and almost all of the precipitation in the prefecture flows into
Lake Biwa via 460 streams of various size. The Seta River is the lake’s only natural outlet. Lake Biwa is
surrounded by 21 municipalities. Peripheral mountains reaching 600-1,000m above sea level encircle the lake
and its surroundings, forming the Omi Basin. Annual mean temperature is 12-14oC. A total of 70 aquatic plants
have been recorded from Lake Biwa, including emergent, floating-leafed and submerged plants. The naturalised
plants, Elodea auttallii and Egeria densa, also occur. The most notable vegetation in Lake Biwa’s coastal areas
consists of vast reed zones comprising Zizania latifolia, Scirpus fluviatilis, Typha angustifolia and Scirpus
lacustris. Outside the reed zone are coastal forests dominated by willows and alders.
Ocean beach flora such as Vitex rotundifolia, Calystegia soldanella and Lathyrus maritimus are also seen,
representing relict plants. The Japanese black pine, a relict here, is distributed mainly on the west coast of the
northern part of the lake, suggesting that Lake Biwa was connected to the sea in ancient times. Lake Biwa is
inhabited by 53 species of fish, including 11 indigenous species. A total of 172 bird species have been recorded
from Lake Biwa and its vicinity. The lake’s coastal areas are used by large numbers of small birds and waterfowl
for feeding and roosting during wintering and migration. Annual January waterfowl counts record over 50,000
birds every year, including Cygnus c. columbianus, Anser fabalis and others.
Conservation issues: Japan’s Ministry of Construction owns 65,448 hectares of the site, while 154ha is in private
hands. The Lake Biwa Ramsar site is included in the Lake Biwa Quasi-national Park Special Zones, as designated
by the Natural Parks Law. It is also included in the Lake Biwa Wildlife Protection Area, as designated by
the Wildlife Protection and Hunting Law. Within the Special Zone, construction or installation of artificial
structures, cutting of trees and bamboo, collection of soil and stone, landfills etc, are prohibited unless prior
permission is obtained from the Governor of Shiga Prefecture. Most of the land in the site consists of beaches or
natural and urban park zones and these are used for tourism and recreation. A great number of sightseers,
swimmers, and more recently those interested in yachting and wind surfing, visit the lake every year. Several
autocamps have recently opened, attracting increasing numbers of people. Lake Biwa has long been a good
fishing ground. Annual fishery production from Lake Biwa is 4,703 tons (1990), including 1,116 tons of
Plecoglosus altivelis, 250 tons of Carassius auratus and 211 tons of carbicula shellfish. In addition, 1,092 tons
of fish and 435kg of pearls are produced by aquaculture. Flooding is significantly reduced in the downstream
regions as flood effluents from streams are held transiently by Lake Biwa and then discharged downstream via
the Seta River. Recently, however, floods and drought associated with changes in water level have occurred. The
increasing demand for water supply, due to population growth, lifestyle change and industrial development, has
necessitated a reassessment of the use of the lake’s water resources. Recent problems include overgrowth of
plankton, eutrophication and nature loss and aesthetic degradation resulting from development of the
surrounding regions. Water quality varies with depth and accordingly, the north-west part of the lake is the
clearest with water pollution increasing in the southward direction. An estimated 4.5 billion tons of water flows
into Lake Biwa annually, 10–20% of which is underground water. Efforts to prevent the progress of
eutrophication are under way. A large number of research institutions, including the Shiga Prefectural Lake
Biwa Research Institute, have compiled a vast amount of data on Lake Biwa.
Izu-numa and Uchi-numa 38°43’N/141°06’E 559 1985
Principal features: Two interconnected freshwater lakes (7m above sea level; catchment area 5,185ha) lying in
an alluvial plain and surrounded by rice fields, giving way to hills (rising to 40–50m a.s.l.) to the south, west and
north. Izu-numa, the larger of the two lakes, has one inflow and one outflow river, the latter flowing into
Uchi-numa, which also has a single outflow (via a flood gate), but two other inflow rivers. The lakes support
fringing peat swamp with beds of Phragmites australis, Zizania latifolia, Phalaris arundinacea, Carex
cinerascens and Scirpus radicans, while the submerged aquatic vegetation includes Trapa japonica, Nelumbo
nucifera and Potamogeton distinctus. The principal human activities within the site are nature conservation and
fishing, while land use in the catchment area includes rice-growing, pastoralism and habitation. The lakes’ water
is utilized for rice cultivation and the wetland performs a valuable flood control function. The site is particularly
important for water birds in winter; it is used by about 80% of the total numbers of Anser fabalis and A.
albifrons wintering in Japan, and by about 20% of the country’s wintering Cygnus cygnus and C. columbianus.
The area is also one of the few Japanese localities for the wild rice community characterized by Zizania latifolia.
Conservation issues: Some domestic effluent flows into the site and the lakes are liable to back-flow from
downstream areas during times of high rainfall. The lakes are becoming progressively shallower owing to
siltation, and Zizania latifolia (wild rice), which is an important food source for wintering swans, is decreasing.
The site plays a valuable role in conservation education, while current research projects (carried out by the
Wildbird Observatory Centre and Izu-numa/Uchi-numa Sanctuary Centre) monitor numbers of wintering water
birds, and investigate reasons for the decline in the wild rice community. Efforts are under way to re-plant areas
of wild rice to improve the food supply for wintering swans.
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