Iriomote Island in Okinawa is now receiving a lot of attention because the National Park area was recently expanded to cover almost the entire island. Being the next promising candidate for a World Natural Heritage Site title, an investigation was conducted. The purpose of this study is to investigate the history of land use in Iriomote from the 1960s and analyze the transition as well as its sociocultural backgrounds to extract the factors that may affect land use. Land use analysis and a field research were conducted, the former was conducted by analyzing topographical map with scale 1/50,000 and aerial photographs, and the latter was conducted to obtain actual land use data. Interviews were also used to reveal historical backgrounds. The results show that the changes in land use have been mainly affected by demographic changes, this is closely related to the changes in lifestyle and culture. Significant differences found in land use between the western and the eastern parts of the island were attributed to the history of the villages.

抄録全体を表示

From 1972 to 1974, HI antibody titer against rubella virus among the inhabitants was evaluated in Ishigaki, Iriomote, Kuroshima, Aragusuku and Yonaguni islands of Yaeyama archipelago, Okinawa Prefecture. The date of onset, size and other charateristics of the rubella epidemics in the past was retrospectively inferred by the date on the rates of the antibody positive individuals among each age groups of the islanders. The antibody positive infants were few im number, and the occurrence was sporadic in the communities throughout the archipelago. While the rate of the positive individuals was about 30 per cent among the younger school-children, it leaped to such a high level as 80 per cent or more in the older classes. This age of the leap was variable among the communities depending on their demographic, geological and social conditions, ranging 7 to 10 years of age. It is presumed that such a variance of leaping age in each communities reflects the course of the rubella epidemics which invaded Okinawa island in 1964 and then propagated southward to the Yaeyama archipelago.

抄録全体を表示

The aim in this study is to clarify a size distribution of fukugi trees in the villages by measuring tree trunk, and use of fukugi as building materials by hearing from residents. It was surveyed in 13 areas in Okinawa. The size distribution in each survey area was similar in spite of a difference of their historical backgrounds. This seems to be caused by cutting trees following the shortage of commodities for several years after war. In those days, cutting fukugi trees not only supplied building materials to residents but also brought a safety windbreak forest surrounding houses.

抄録全体を表示

The larval habitats of tabanids were surveyed at Ryukyu Islands in 1974,1980 and 1981. In total 5,1,2,4,and 2 species were collected at Okinawa, Miyako, Ishigaki, Iriomote and Yonaguni Islands, respectively. Hirosia kotoshoensis and Hi. masamitsui were mainly breeding in wet mosses, while Atylotus angusticornis was breeding in tidelands. Tabanus taiwanus and Chrysops vanderwulpi inhabited mainly in illdrained paddy fields. Injuries on a farmer's legs caused by the bite of tabanid larvae (mostly T. taiwanus) was observed.

抄録全体を表示

We studied the seismic activity in and around Iriomotejima Island, SW Ryukyu Arc, Japan, during the period from January 1992 through May 1993. In particular, two earthquake swarms, namely, the swarm which occurred off the SW coast of Iriomotejima Island late in August (SW swarm) and that occurred in the NW region of the Island in the middle of September 1992 (NW swarm), were investigated in detail in this paper. The data used in this study were restricted to “felt earthquakes” whose amplitudes were larger than 1gal. As a result, the number of events was not so large, but homogeneous in time and space.
The spatial and temporal characteristics of these seismic activities are summarized as follows;
1) A high swarm activity in the SW region continued several days. The focal zone extended to the NW-SE direction.
2) The focal region of NW swarm migrated from off the NW coast of the Island to the inland area and then expanded to the surrounding areas.
3) The focal zones extend in the NW-SE direction. And the vertical distribution of hypocenters shows a sharp seismic boundary plane. This is consistent with the predominant direction of the fault strikes and lineaments in this region.
4) Some of the remarkable features observed in the later phases appear to represent reflected waves. These features suggest a possibility of the existence of sharp reflectors such as a magma reservoir beneath the region. However, no signs were seen for any surface volcanic activity.
In consequence, it is considered that these earthquake swarms occurred under the stress field acting in the wide area of the SW Ryukyu Arc.

抄録全体を表示

　八重山諸島周辺海域を分布北限とする熱帯性海草ウミショウブは環境省RDBに絶滅危惧II類として掲載されているが，本種の分布・群落状態および生育環境の定量的条件に関する情報は乏しい．そこで西表島北西部のウミショウブ分布範囲について当該海域の通常の高波浪条件を用いた外力分布再現計算を行い，この結果と，同海域のウミショウブ分布の調査結果とを直接比較し，ウミショウブの密生かつ草丈の長い群落は，D.L. -0.76mまでの水深で, 通常の冬季高波浪時の平均有義波高25～32cm，平均底面流速11～19cm/s，大潮時平均残差流速0.1～0.3cm/sを中心とする範囲に分布していることが明らかになった. この条件を物理環境の再現計算結果に当てはめると，おおむね現状の群落分布が再現され，ウミショウブの群落分布には物理条件が大きく影響することが明らかになった．

抄録全体を表示

A flock of Oriental White Storks appeared in Yonaguni Island, the westernmost Japan in November 1993. The flock size at the time was eleven. The communal roost that was formed in a lowland valley with paddy field seems to have been shifted to another paddy field area during a short period in March 1994, probably due to human disturbance at the former place. Another important habitat for storks was pasture where they foraged. The flock of eleven storks were never recorded after December, but it is highly probable that the eleven birds overwintered in the island, since roosting of a single bird apart from the communal roost with ten birds was suggested for a night in February. Large flocks at the communal roost were recorded last on 19 March and thereafter one or two storks were witnessed until the summer of the year.

抄録全体を表示

　本研究では，観察・実験結果に基づいた数値解析を実施し，西表島北西部におけるウミショウブの果実分散による移動距離，果実による群落間の交流および消失群落の回復の可能性を検討した．
　その結果，本研究の計算領域内におけるウミショウブ果実の平均および最大移動距離は，それぞれ879～2,494mおよび9,727～15,403m（果実の浮遊時間は，最小で約30秒，最大で26日間）であることが明らかとなった．これは，ウミショウブ種子の平均浮遊時間2.4時間の平均移動距離261mに比べて大きなものであり，果実分散によって分布を拡大してきたことが示唆された．さらに，極めて低い確率であるが，離れた群落間の果実交流や消失した群落の回復の可能性が示された．

抄録全体を表示

This paper aims to analyze the distribution and placement of settlements (Shuraku) on Taketomi Island, Yaeyama, Okinawa. The settlements of Taketomi Island consist of living areas (Kyoju-iki) and sanctuaries, known as Wons or Utaki. The zones of residence are in an approximately central location with a number of defined sacred areas dotted around them. In order to clarify the relationship between the living areas and the sacred areas, a detailed analysis of the location, construction, and composition of the ritual function was carried out through a review of the organization and planning of the "Pui" harvest ritual. Data were collected and recorded from a series of field studies and reference review.

抄録全体を表示

1.四日市南高校山岳部を主体として,八重山群島西表島の調査が実施され,1965年8月15日から25日にかけて,西表島及び仲ノ神島の鳥類を調査した。
2.今回の調査により,本島産新記録種7種を含めて22科38種の鳥類を記録した。これらのうち本邦との共通種は32種,台湾とのそれは37種であり,亜種まで一致するものは,本邦について19種,台湾について21種である。これは本島産の鳥類の構成が地理的に近い台湾との共通性の深いことを示しているといえる。
3.南西諸島は東洋区,旧北区との境界として,動物地理学上重要な地域であり,本島においても地理的及び生態的分布上の注目種として,スズメ,シマアカモズ,リュウキュウツバメ,アオツラカツオドリ,オオアジサシ,リュウキュウキジバトがみられた。
4.西表島南方の仲ノ神島には,クロアジサシ,セグロアジサシ,オオミヅナギドリ,及びカツオドリの4種の海鳥が繁殖しており,総個体数約20,000羽を記録した。それらのうち,クロアジサシ,セグロアジサシの両種間にはすみ分けがみられた。
5.仲ノ神島では毎年産卵期に採卵が行なわれており,今後貴重なる海鳥の大繁殖地として保護対策が早急に必要であると考える。

抄録全体を表示

(1) 1982年8月9日,中型の強い台風11号が仲の神島をほぼ直撃する進路をとって北上した(Figs.1-4)。台風通過後9日目の8月18日に台風による被害調査を行ったところ,Table 1に示すように,繁殖中の4種の海鳥類の死体を発見した。
(2) セグロアジサシについては,台風来襲前後の繁殖状況調査,標識鳥の死体回収,主副集団営巣地の台風後の状況などから,台風来襲直前に棲息していた幼鳥の少なくとも10数%以上がこの台風で死亡したと推察される。
(3) 主に海岸線の岩石累積地帯で営巣しているマミジロアジサシとアナドリの繁殖は壊滅的な被害を受け,主に崖地や岩棚で営巣しているカツオドリとクロアジサシも相当な被害を受けたであろう。

抄録全体を表示

This study aimed to explore the spatial composition and maintenance of “Utaki”（traditional sacred space） and the management of the local festivals at Kabira, Taketomi, and Hoshidate in the Yaeyama Islands, Okinawa. A spatial survey of Utaki was conducted. Further, the officers of the organization of community centers that holds each of these local festivals were interviewed. In Kabira, Utaki have a closed spatial composition and are managed by parishioners that migrants from outside the prefecture are not allowed to participate. Prayers are conducted in Utaki by a female priest called “Tsukasa” in most of the local festivals. In Taketomi, the management of Utaki differs depending on their rating in the village. Utaki have an open space like a shrine. The organization of community centers conducts festivals in which all the islanders participate. The migrants can also participate in these festivals. In Hoshidate, the organization of community centers plays a major role in the management of Utaki. Some Utaki are used as tsunami shelters and windbreaks. The organization where migrants serve as executives holds traditional festivals along with contemporary events. The above results show that the spatial composition of Utaki and the local festivals differed among the three regions. Based on this, the study makes the following suggestions. If the traditional organizations remain like in Taketomi, it is important to manage the organization to educate migrants about Utaki and the local festivals. However, if the traditional organizations are weakened, as in the case of Hoshidate, it is important for the organization of community centers to maintain traditions by making them easily accessible for the younger generations and migrants.

抄録全体を表示

　八重山諸島に分布する熱帯性海草ウミショウブEnhalus acroidesは環境省レッドデータブックの絶滅危惧II類に掲載されている．本種は種子による分散力が低いことが知られており，本種の保全には分布可能条件を明らかにする必要がある．本種の2013年の群落分布と，SWANによる2015年の1年間の月ごとの有義波高と底面流速分布の再現計算結果とを比較し，これらによりウミショウブの分布を説明することができた．また，海域が静穏である6月の外力状況ではウミショウブの分布可能とされた範囲は過大であったが，台風などのイベント発生時期や冬季の高波浪時の外力を用いると分布判断のエラーが少なかった．1989年に調査された分布と2013年の分布を比較したところ，外力の外縁部で群落が消滅していた．

抄録全体を表示

近代八重山の廃村は，そのほとんどがマラリアによる人口減少が原因とされてきた．しかし一方で，マラリア禍の激しかった西表島において500年以上も存続してきたのような集落も存在する．本稿では，近代廃村期（1900年から1938年）を生き延びたマラリア有病地集落共通の特徴を分析し，その集落存続要因を探った．その結果，不明な点の多い伊原間集落を除き，八重山のマラリア有病地存続集落はすべて蔡温施政期以前からの古集落であった．古集落は，良港や湧き水の存在など立地条件がもともと良く，生活基盤がすでに整備されていたため，近世の地元役人による不正な課税に苦しみながらも人口を維持し得たと考えられる．また，近代廃村期における石垣島と西表島の廃村状況およびマラリア罹患率の違いから，マラリア予防対策は西表島の方がより効果があがったことが明らかになった．資料の多く残る西表島の古集落を事例として検討したところ，住民による自発的集落移動や予防事業への全面的協力があった．のような古集落には，人口減少を回避する強い集落内結束があり，こうした人間関係を基にした社会構造が，マラリア禍を緩和し，集落存続のための生存戦略を生む背景となっていたのである．

抄録全体を表示