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The Natural Environment and Ecosystem of Dokdo

HOME > Marine Science Reports > The Natural Environment and Ecosystem of Dokdo
Being more than 200 km away from the mainland, Dokdo has been relatively free from human impact and therefore has a natural environment that has been relatively well-preserved. At the crossroads of warm currents and cold currents, the sea surrounding Dokdo is home to both marine animals that inhabit warm seas and those that live in cold seas. The waters of Dokdo thereby have more biodiversity than at any spot far out in the East Sea. Dokdo is also a resting place for migratory birds on their way across the East Sea towards Siberia. The significance of Dokdo’s natural environment and ecosystem led the Korean government to designate Dokdo as Natural Monument No. 336 on November 4, 1982. On December 13, 1997, Dokdo was designated as a Specified Island under the ‘Special Act on the Conservation of the Ecosystem in Dokdo and other Island Areas’, and has been managed under the Cultural Heritage Administration’s announcement number 1999-95 on the ‘Dokdo Nature Protection Zone’ set forth on December 10, 1999. In 2000, the Ministry of Environment also established Dokdo as a ‘Specified Island’ through its public announcement No. 2000-109.
Located in the middle of the sea, Dokdo has a typical marine climate. Annual precipitation amounts to 1,383.4 mm, which is similar to the average in Korea. Rain in Dokdo, however, is not concentrated in the summer rainy season, but is spread rather evenly throughout the year. Winter brings snow instead of rain, but due to steep inclines and strong winds, snow does not tend to pile up.
The yearly average temperature in Dokdo is 12.4°C, with the monthly average for January at 1°C and the average for August at 23°C. Compared to Seoul, where the average temperature in January is -2.6°C and in August 25.4°C, Dokdo has a smaller seasonal temperature difference, most likely due to the fact that Dokdo stands in the middle of the sea.
The terrestrial ecosystem of Dokdo
Dokdo was created by lava that hardened after a volcanic eruption. Over 2.7 million years, some of this volcanic rock wore away into a thin layer of soil cover that is only 30cm deep. With its steep inclines, there is really not that much soil suitable for sowing and germinating seeds. Rain water also washes the soil away, leaving very dry soil in its wake, while a strong salty sea breeze tends to dry out any plants that have managed to start growing. A such, Dokdo is not very accommodating to plants. Still, in spring, Dokdo is abloom with an explosion of wild flowers that persevere in the face of such adverse conditions.
About 80 plant species have been identified on Dokdo. Some are quite familiar to us, such as the dandelions, plantains, Siberian chrysanthemums, blumei, zebra grass, tiger lilies, spindle trees, black pines, sweet biers, large pinks, goosefoot plants, the sea chrysanthemum and wild grapes. Others, with their interesting names, are not so familiar.
Dokdo flower
50 different insect types have been found on Dokdo, including 2 Libellilidae, 1 earwig, 2 grasshoppers, 9 Pentatomidae, 8 cicadas, 1 neuroptera, 15 cleoptera, 8 flies and 7 different butterflies. The cleoptera are most diverse in terms of insects.
During the spring breeding season, the skies of Dokdo are filled with black-tailed gulls. All crevices and grassy areas are taken over by their nests, in which 2 to 3 oval-shaped eggs are usually waiting to hatch. In early summer, gull chicks will start practicing with their mothers to soon take flight.
Other sea birds that live on Dokdo include: the pelagic cormorant, Swinhoe’s storm-petrel and the shearwater. Dokdo’s designation as Natural Monument No. 336 was dependent on the fact that these birds chose Dokdo as their breeding grounds.
There are almost 30 types of birds that are observed in Dokdo in May, including the night heron, cattle egret, Japanese wood pigeon, hawks, black-tailed gulls, dusky thrush, blue rockthrush, Siberian meadow bunting, daurian redstart, the finch, oriental greenfinch and the raven. In October, you can see 20 or so different types of birds such as the black kite, hawks, the kestral, Japanese wood pigeons, skylarks, grey wagtails, the daurian redstart, the dusky thrush, rustic buntings, the black-faced bunting, the finch, the oriental greenfinch and the russet sparrow. The number of bird species differs according to the season as birds stop by in spring and autumn to rest briefly on their migration route. In all, 120 different types of birds have been observed in Dokdo.

In the past, sea lions used to inhabit the rocks surrounding Dokdo, but are no longer to be found. The only memory of the sea lions can be found in a rock named ‘The Ga-je (Sea Lion) Rock’, where the sea lions used to rest.

There are no native terrestrial mammals on Dokdo. The only terrestrial mammal on Dokdo is the Sapsari, a native Korean dog brought onto the island by the Dokdo police guard.

Amphibians and reptiles have never been discovered on Dokdo.
The marine ecosystem of Dokdo
The waters of Dokdo are full of life. Forests of seaweed dance with the waves, and many fish swim in and out through these seaweed forests.
Included in the green algae found near Dokdo are the sea-staghorn and sea-lettuce. Brown algae include Eisenia bicyclis, Sargassum sp., Undaria pinnatifida and Ecklonia cava. Red algae found near Dokdo include Porphyra suborbiculata, Gelidium sp. and coralline algae. Reports say that about 160 different kinds of algae can be found in the waters of Dokdo. This is most likely because the seabed near Dokdo consists of hard rock that is suitable for algae to grab onto and grow. This thick forest of seaweed is a great habitat for marine animals to live in, as algae sometimes becomes food and sometimes provides a hiding place for the animals.
‘Benthos’ are marine animals that grow on rocks or crawl on the bottom of the seas. Rocks on the coast of Dokdo are frequently covered completely by barnacles and mussels. Gastropods in the mollusk family such as Thais (Reishi) bronni, Cellana toreuma, Thais (Reishi) clavigera, Granulilittorina exigna, Omphalus pfeifferi and the Cellana grata can also be found in the Dokdo seas. Mollusks are animals with soft bodies like shellfish and cuttlefish, while gastropods are those mollusks with a single shell, like the conch. Crustaceans including crabs and lobsters also roam the seabed near Dokdo, as do spiky echinoderms such as the Hemicentrotus pulcherrimus, the Far Eastern Violet Sea Urchin, sea cucumbers and the Northern Pacific Sea Star. Sea cucumbers, sea urchins and gastropods such as the spiny turban shell and abalones all comprise some of Dokdo’s very important fisheries resources.
One important catch from Dokdo and Ulleungdo that should also be mentioned is the common flying squid. From spring to autumn, the night sea is lit as bright as day by the lights of fishing boats out to catch the squid by drawing them close with their bright lights. While in the past, the squid were not available in the cold waters of winter, they are now even caught during the winter months due to the influence of global warming.
The waters of Dokdo hold an abundant store of fisheries resources. The Tsushima Warm Current splinters from the Kuroshio Warm Current and passes through the Korean Strait into the East Sea, and then flows north towards Ulleungdo and Dokdo, greatly influencing the marine environment there. This warm Tsushima current meets with the cold North Korean current near Dokdo, ensuring that a wide variety of marine animals can be found in the vicinity. The ‘Island Effect’ of Dokdo also increases the number of plant and animal species found in the Dokdo area. As seawater collides with the island, the Island Effect forces the upwelling to the surface of deep sea water that is rich in nutrients. This nutrient-rich deep seawater is pulled up to the surface and provides more nutrients for phytoplankton to flourish. This in turn attracts more zooplankton, which attract small fish, which attract bigger fish - turning the area into rich and diverse fishing grounds.
Phytoplanktons that can be found in the seas of Dokdo include diatoms, dinoflagellates and Chrysophyceae. Doing the work that plants would do on land, phytoplanktons take in sunlight to produce organic materials. The well-being of a marine ecosystem depends heavily on the abundance of phytoplankton, the primary producers of these organic materials. Zooplankton that are found near Dokdo include Siphonophora, Scyhozoa, Copepoda, Cladocera, Ostracoda, Amphipoda, Decapoda, Euphausiacea, appendicularians, arrow worms, Thaliacea and various planktonic larvae. Although too small to be seen by the naked eye, the abundance in phytoplankton and zooplankton in the waters of Dokdo is exactly what makes this area one of the best fishing grounds in the world.
More than 100 fish species inhabit the seas of Dokdo. Some are very familiar, such as anchovies, the yellowtail, mackerel, the jack mackerel, the striped beakperch, the bulgyhead wrasse, pilchards, herring, pollack, cod, mackerel pike, salmon, the black rockfish, the sailfin sandfish, the whitesaddled reeffish, filefish and the flounder. Some fish are less well-known - such as the pinecone fish, the john dory, the greening, the golden-striped amberjack, the Indo-Pacific sergeant, the cocktail wrasse and the Japanese blacktail triplefin. At times in the year when water temperatures rise due to the influence of the Tsushima Warm Current, subtropical fish such as the blue-striped angelfish, the half-lined cardinal and the candystripe cardinalfish can also be found in the seas of Dokdo. Whitesaddled reeffish, the smokey chromis, the hardscale soldierfish, the fourstripe cardinalfish and other fish that are usually found in the seas of Jejudo can also sometime be found near Dokdo.
The beautiful natural scenery, high biodiversity and rich fisheries resources found in Dokdo all combine to underscore the value of Dokdo as a very unique ecosystem. For us to be able to utilize these resources in a sustainable manner, we need to gain a deeper understanding of the ecosystem of Dokdo, and work to protect its environment and ecosystem. Only when such efforts are exerted will we be able to ensure the health of the ecosystem of Dokdo while enjoying the benefits that Dokdo can offer us.