Nature & Parks

The First National Report - Chapter 2

[International Cooperation] The First National Report under The Convention on Biological Diversity

Chapter 2. Background of Measures for Biological Diversity
-Present Status of Biological Diversity in Japan

2.1 Features of Natural Environment

Japan is located to the east of the Eurasian Continent. It is an island nation in the shape of a crescent and extends 3,000 km long. It has 3,000 m-class mountains above sea level and three-fourth of its national land is covered by undulating mountainous areas.

The climate in Japan ranges from subtropical to subarctic zones. It is temperate and humid, and has clear seasonal difference due to the influence of seasonal monsoon wind. The steep topography with mountains and valleys contributes to the variety of climate in Japan. The climate in Honshu, in particular, is distinctively divided by the central mountain ridges.

Japan has four main islands and over 3,000 small islands. Because it is surrounded by sea, its biota is characterized by an insular nature and some islands have unique biota.

The varied climate and topographical conditions of the Japanese archipelago as well as its geological history of repeated connection to and separation from the Asian continent during the formation of the Japanese archipelago have largely influenced the makeup of biological diversity in Japan.

[International Cooperation] The First National Report under The Convention on Biological Diversity

Chapter 2. Background of Measures for Biological Diversity
-Present Status of Biological Diversity in Japan

2.2 Ecological Diversity

Japan has been carrying out the National Survey on the Natural Environment to obtain knowledge of the status of the nation's natural environment. Based on the Survey, a vegetation map (scale 1: 50,000) covering the entire national land was prepared and revised on a regular basis.

According to the results of the Fourth Survey (1988 to 1992), Japan's national land consists of forests (67.0%), paddies and fields (22.8%), grasslands (4.4%), and urban and developed areas (4.2%). Classifying by the degree of artificial influences, Japan has secondary forests and secondary grasslands, planted forests, paddies and fields, and urban and developed lands.

[Forests]

Forests occupy 67.0% of the national land, performing the important role as wildlife habitat. Forests in Japan consist of natural forests (26.9%), secondary forests including woody hills near cities (35.9%), and planted forests such as forests of Japanese Cedar or Japanese Cypress (37.2%).

Natural forests in Japan include various types: coniferous forests and coniferous broad-leaved mixed forests in the boreal or alpine zone, deciduous broad-leaved forests in the temperate zone, and evergreen forests in warm temperate subtropical zone. Large-scale natural forests can only be found in Hokkaido, which houses 59.5% of all natural forests in Japan. Natural forests of nearly the same sizes are found on mountainsides in the northeastern and central regions of Honshu and on the southwestern islands. In other parts of Japan, natural forests are distributed in alpine areas or on solitary islands in much smaller scales.

Secondary forests are located near human habitation and have been utilized for the production of firewood or charcoal and the gathering of fallen leaves, etc. At the same time, these forests also serve as the habitats for various animals and plants that are dependent on such environment.

Forested area in Japan only decreased slightly in recent years. Detailed data show that secondary and natural forests have been decreasing while planted forests have been increasing slightly. Vegetation succession has proceeded at some secondary forests due to a drop in human activities such as the gathering of wood for fuel, resulting in a decline in forest conservation efforts.

[Grasslands]

Grasslands account for only 4.4% of vegetation in Japan. They are scattered in the nation on the mountainside as pastures, grazing grounds, and so on. Grasslands are important habitats for wildlife that is peculiar to grasslands such as the continental relic species.

However, due to the decline in grassland utilization caused by various factors such as a decrease in human activities like weed burning to maintain its vegetation, succession has been proceeding. It is feared that species depending on grasslands will also decline in number.

[Wetlands]

Although wetlands occupy very small percentage of the whole vegetation in Japan, they provide an important ecosystem as the habitats for wildlife. The wetlands in Japan are basically categorized into two types: one is the wetland mainly made up of aquatic mosses cultivated by rainfall, the other is mainly composed of ditch reeds and is distributed in the middle and lower reaches of rivers. These wetlands are distributed in wide regions from Hokkaido to Okinawa. The latter type has been affected by human activities such as development projects because it is adjacent to the living sphere of humans.

[Rivers and Lakes]

The ecosystem at rivers and lakes is formed by a combination of water areas, riverside and lakeside. Rivers and lakes provide habitat not only for aquatic species but also for vegetation peculiar to riverside and small animals or aquatic birds, which depend on their vegetation.

On the other hand, riparian land has been utilized intensively in Japan. Human activities have brought many modifications to the riparian environment. According to the Third National Survey (1985) of artificial modification to the shoreline of rivers from the river mouth to the upper reaches of the main stream of 113 rivers, including the main stream of 1st-class rivers (totaling 11,412 km long), 21.4% of the shorelines has artificial structures. According to the Fourth National Survey (1992) of artificial modification of 153 rivers, including the major 2nd-class rivers and tributary streams of the 1st-class rivers flowing through areas of good natural condition (totaling 6,249 km long), 26.6% of the shorelines has artificial structures. Regarding the status of fishes, fishes were able to swim up to the upper reaches in 27 of the 74 main streams, or 80% of the total length in the 37 streams being surveyed. At 50 of the 79 tributary streams where fishes swimming upstream had been sighted, fishes were able to swim from the river mouth of the main stream to the upper reaches in 7 rivers, and swim up to 80% of the total length from the river mouth in 22 rivers.

Similarly, at brooks and waterways on the plains, the habitats of aquatic species have disappeared or become fragmented because the construction of dams and artificial structures in waterways has separated these habitats from the mainstreams.

[Coastal Areas]

Natural coast maintains the natural inter-tidal zones, which are important as the habitat or cradle for the reproduction of wildlife. In Japan, however, coastlines have been artificially modified mainly during Japan's rapid economic growth. According to the results of the 1993 National Survey, 38.0% of the 19,134 km coastlines of the four main islands were artificial coastlines, where structures have been constructed at the inter-tidal zones for shore protection. The decrease of natural coastlines continues.

Tidal flats provide the environment for benthos especially in the coastal areas. They serve as important habitats for various coastal fishes and migratory birds such as snipes and plovers. In Japan, many of the tidal flats are located along inland seas and inner bays where a high concentration of population and economic activities are evident. Thus, tidal flats are disappearing due to development projects such as land reclamation and other reasons. According to the results of the National Survey undertaken between 1989 and 1991, tidal flats in Japan totaled 51,433 ha. Since 1978, 3,857ha have disappeared.

Coral reefs in the southwestern islands of Japan mainly composed of fringing reefs. Although coral reefs in Japan are found on the northern limit of the world's coral reef distribution, the warm Kuroshio Current along the Pacific Ocean side of Japan has blessed the nation with a good variety of hermatypic corals.

However, in the sea areas of the southwestern islands, coral habitats have been damaged because of predation by the crown-of-thorn starfish and sedimentation of red clay. Except a few, these habitats have not been restored. According to the results of the National Survey on coral reefs undertaken for three years from 1989 at the coral reefs in the sea areas of the southwestern islands, coral communities in sound living condition was observed only in 8% of the area where corals used to inhabit.

[International Cooperation] The First National Report under The Convention on Biological Diversity

Chapter 2. Background of Measures for Biological Diversity
-Present Status of Biological Diversity in Japan

2.3 Species Diversity

Many kinds of animals and plants inhabit in Japan, including 188 species of animals (the number includes subspecies, same hereinafter), 665 species of birds, 97 species of reptiles, 64 species of amphibians, and 7,087 species of vascular plants and so forth, showing the existence of rich biota in this rather narrow land. These fauna and flora also include many endemic species. For example, about 35% of gymnosperms plants and angiosperms are native species.

The biota in Japan was formed by the various topographical and climate conditions as well as its history of repeated connection to and separation from the Asian continent during the formation of the Japanese archipelago. Such diverse conditions had been kept throughout the long history of Japan until the modern times. However, since the process of modernization started, especially after World War II, the environment of the national land has been changed drastically. Development in the era of rapid economic growth resulted in the decline and disappearance of wildlife habitats, and subdivision and pollution deteriorated the condition of habitats. Furthermore, the over exploitation of rare animals and plants threatens the existence of many species in Japan.

In 1991, the Environment Agency issued the Red Data Book of Japan for animals. Since then, the Red Data Book has been reviewed by taxonomical group. Review of the Red List for the amphibian Data Book was completed in August 1997. The Environment Agency also issued the Red List for plants in August 1997. According to these lists, about 7% of mammals, 8% of birds, 19% of reptiles, 22% of amphibians, 11% of brackish and freshwater fishes are listed as threatened species, and about 20% of vascular plants species are deemed as similarly threatened.

There are still many unknown areas with regard to the diversity of species in Japan. For example, it is estimated that there are 70,000 to 100,000 insect species in Japan but the named species are only about 30,000. It is difficult to find out the distribution of species in the whole country since many areas do not have information available. Therefore, it is urgent to gather basic information to find out the status of biological diversity in Japan.

[International Cooperation] The First National Report under The Convention on Biological Diversity

Chapter 2. Background of Measures for Biological Diversity
-Present Status of Biological Diversity in Japan

2.4 Genetic Diversity

All species have genetic diversity within species; therefore, it is important to preserve biological diversity at the genetic level. To protect genetic diversity within species, the preservation of local populations, which are groups within the same species separated geographically by islands or water systems, is essential.

According to the Red Data Book (1991) issued by the Environment Agency, the existence of 32 local populations such as mammals, amphibians, freshwater fishes, and snails in Japan is threatened at present.

Also, generic disturbance of local populations is widely observed due to artificial transportation or introduction of individuals into other populations. There is concern that the genetic diversity of respective regions may disappear.

In Japan, the structure of and disturbance to the genetic diversity of wildlife are not sufficiently known. Given the disappearance of so many local populations, it is urgent to find out the status of genetic diversity and to identify the problems.


Ministry of the Environment Government of Japan

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