Tottori Sand Dunes

Sand dunes on the coast of the Sea of ​​Japan in eastern Tottori Prefecture. A collective term for the Fukube and Hamasaka sand dunes on the eastern side of the mouth of the Sendai River, and the Koyama sand dunes on the west bank, the dunes stretch 16km east to west and 2km north to south. In the strict sense, the Tottori Sand Dunes refers to the Hamasaka sand dunes, which, at 92m high, are the largest in Japan and resemble an inland desert. The ecology of plants and animals in the sandy environment is academically valuable, so the eastern half has been designated a national natural monument and is also part of the San'in Kaigan National Park.

At the bottom of the depression called Suribachi, a colony of sand plants that fights against blowing sand forms an island-like green space, and the further inland you go the more stable it becomes, but insectivorous creatures such as the wolf spider live in holes to avoid the hot summer surface of the sand dunes. The main force in forming the current sand dunes is the northwest monsoon winds in autumn and winter, with wind ripples occurring at wind speeds of around 2 meters per second and sand storms occurring at speeds of over 10 meters per second, which change the sand dunes. The stratigraphy is made up of the current sand dune layer sandwiched between a layer of humus black sand, a layer containing Jomon and Hajiki artifacts, a layer of black soil, a layer of Daisen volcanic ash, a layer of fossil-like old sand dunes, and a bedrock bed, which tell the story of the lowering of sea levels and the development of old sand dunes since the Würm glacial period, the accumulation of volcanic ash and the habitation of prehistoric people, and the formation of new sand dunes.

From 1785 (Tenmei 5), new farmland development began following erosion control reforestation, but from 1896 (Meiji 29) the area became a training ground for the Tottori Regiment, and the three sand dunes remained.

After the Second World War, large-scale afforestation with black pine and black locust trees was carried out to prevent sand from eroding, but the movement of sand from the northwest to the natural monument area weakened, and grassland spread, so after many years of debate over whether to protect cultural properties or green the area, 50.5 hectares of protected forest upwind were cut down. There are tourist facilities such as Tottori Sand Dunes Children's World (opened in 1973), and about 1.5 million people visit the area annually (2004).

The western half of the prefecture is home to the Tottori University Arid Land Research Center, which conducts international research, but agriculture in the surrounding sandy areas, with the exception of scallion cultivation on the Fukube Sand Dunes, has declined due to the development of housing complexes.

[Minoru Iwanaga]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

鳥取県東部、日本海沿岸の砂丘。千代(せんだい)川河口東部の福部(ふくべ)、浜坂(はまさか)砂丘、西岸の湖山(こやま)砂丘の総称で、東西16キロメートル、南北2キロメートル。狭義の鳥取砂丘は浜坂砂丘をさし、最高点92メートルの日本最大の起伏が、内陸砂漠の景観を思わせる。砂地環境下での動植物生態が学術的に貴重なことから、東半部は国の天然記念物に指定され、山陰海岸国立公園にも属する。

　スリバチとよばれる凹地底には飛砂と闘う砂地植物の群落が島状の緑地をなし、内陸へ行くほど安定度を増すが、イソコモリグモなどの食虫類は、夏高温の砂丘表面を避けて穴居している。現砂丘形成の主営力は秋季、冬季の北西季節風で、風速2メートル内外では風紋(ふうもん)が、10メートル以上では砂嵐(すなあらし)が生まれて砂丘を変化させる。層序は上から腐植黒砂層を挟む現砂丘層、縄文(じょうもん)―土師器(はじき)遺物包含層、黒ボク腐植土層、大山(だいせん)火山灰層、化石古砂丘層、基盤岩床と重層し、ビュルム氷期以来の海面低下と古砂丘の発達、火山灰の堆積(たいせき)と先史人の居住、新砂丘の形成などの過程を物語っている。

　1785年（天明5）以降、砂防造林に次いで新田開発も始まったが、1896年（明治29）以降は鳥取連隊の演習地となり、3砂丘は残った。

　第二次世界大戦後クロマツとニセアカシアによる大規模造林で砂防化は進んだが、天然記念物地域への北西方向よりの砂の移動が弱化し、草原化が進行したので、文化財保護か緑化かをめぐり長年論議のすえ、風上にある50.5ヘクタールの保安林を伐採した。鳥取砂丘こどもの国（1973年開園）などの観光施設があり、年間約150万人（2004）が訪れる。

　なお西半部には鳥取大学乾燥地研究センターがあり、国際的研究を進めているが、周辺の砂地農業は福部砂丘のラッキョウ栽培を除き、住宅団地化で後退している。

［岩永　實］

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