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Ecosystem Ecosystem of the Oki Islands

The ecosystem of the Oki Islands UNESCO Global Geopark is mysterious, even from a global perspective.

Recent research is beginning to unravel the factors behind it.

Here you will find some explanations of the changes in the distribution of vegetation found according to the research on Japanese cedars, and the environment created by the Tsushima Current flowing through the Sea of Japan.

Migration of Plants from Research Findings on Japanese Cedars

Inside the natural forest at the foot of Washigamine Ridge and other locations on Dōgo Island, there are many gigantic Japanese cedar ( Cryptomeria japonica) trees, including the "big four," that are hundreds of years old.

Yao-sugi Japanese Cedar
Chichi-sugi Japanese Cedar
Kabura-sugi Japanese Cedar
Mado-sugi Japanese Cedar

There are mainly 3 types of Japanese cedars: omote-sugi and ura-sugi, distributed along the coast facing the Pacific Ocean and the Sea of Japan respectively, and Yaku-sugi which is found distributed on Yakushima Island.
It has been discovered that the Japanese cedars originally growing in the Oki Islands are ura-sugi, and little by little, studies conducted on Japanese cedars have been unraveling the story of the migration of plants during the glacial period.

The Japanese cedars which could no longer grow in the cold inland area of Honshu took refuge on the warmer coast of the Sea of Japan, particularly on the Oki Islands, which at that time were part of a peninsula.
Later, along with the increase in temperature, Oki became islands, trapping the Japanese cedars that migrated there during the last glacial period. The descendents of those Japanese cedars still remain in Oki, and they carry their own unique genes. These Japanese cedars are a precious treasure of the Oki Islands.
It is speculated that the mysterious plants that make up the vegetation of the Oki Islands may have sought refuge here, just like the Japanese cedars.

Environment Created by Tsushima Warm Current

Vegetation in the Oki Islands is mysterious, as different types of plants that are usually found in very different habitats can be seen together here.
It seems that the changes which occurred in the topography and climate of Japan, with the Oki Islands included, are a clue to understanding the formation of vegetation in the Oki Islands. However, another factor must be considered in order to explain the reason why the organisms can survive in the environment of the Oki Islands, which was originally an unsuitable habitat.

One of the reasons is thought to be the Tsushima Warm Current that flows around the Oki Islands.
The cold north-westerly wind from the continent flows into the warm air from the south of the Sea of Japan. The air then evaporates into clouds, bringing abundant rain, snow, and mist to the regions along the Sea of Japan, including the Oki Islands.
With moderate winter and summer temperatures, year-round rainfall and high humidity, the Oki Islands with their oceanic climate are a suitable habitat for various plants.

The formation of the Oki Islands

Geohistory

Born and raised on the land

Unique Ecosystem

Passed down through generations

Lifestyles and Traditions

?What is an Ecosystem?

All living things, such as plants, animals, and microorganisms living on the Earth benefit from the soil, air, water, and light, and live in the environment. In addition, creatures interact with other organisms living in the same environment. The combination of these living things and the natural environment they inhabit is an ecosystem.
The geology and topography that create the natural environment are also related.
Here in the Oki Islands UNESCO Global Geopark, the ecosystem—the organisms and their habitat—is also considered and introduced as a "geoheritage."

?What is a Species?

Various organisms inhabit the Earth today. There are many differences and diversities among the organisms, but they also share things in common. Organisms are classified into groups based on similar characteristics, and species is the basic unit of grouping. A species is a collection of individuals with common morphological and physiological (physical faculties and tissues) characteristics, and it is possible for individuals of the same species to breed in a natural environment to produce fertile offspring.

Organisms are thought to have evolved from a single species that appeared on Earth long, long ago. From a shared ancestor, types of organisms have increased over time and there are now at least 2 million species living on Earth. These organisms live in various habitats—some fly, some live in trees, some are present in soil, some are aquatic, some dwell in hot climates and some thrive in the cold. In other words, the environments that the various organisms inhabit are also diverse.

Why did organisms with the same ancestor evolve into such a wide variety? Considering factors such as geological changes and relationships with different organisms is a step toward learning about the Earth and about changes occurring in the environment through the organisms.