Expanding walls and shrinking beaches: loss of natural coastline in Okinawa Island, Japan
Expanding walls and shrinking beaches: loss of natural coastline in Okinawa Island, Japan
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DOI：
10.7717/peerj.7520
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发表时间：
2019-09-06
期刊：
影响因子：
2.7
通讯作者：
Reimer, James D.
中科院分区：
文献类型：
--
作者：
Masucci, Giovanni Diego;Reimer, James D.
冲绳是日本南部琉球群岛中面积最大、人口最多的岛屿，以其自然资源和美丽而闻名。与该国其他地区的情况类似，冲绳岛也受到了越来越多的开发和建设工作的影响。这一趋势在美国战后执政27年后于1972年回归日本后尤为尖锐。曾经以珊瑚礁环绕的绵延沙滩为特征的海岸线，现在包括由海堤、护岸和其他人造硬化结构划定的区域。此外，冲绳岛沿海的一部分是通过填海造陆(填海造陆)获得的。然而，目前人工海岸线的延伸以及自然海岸线的碎片化程度尚不清楚，因为既没有已发表的研究报告，也没有易于查阅和更新的数据集。这项研究的目的是量化冲绳岛海岸线变化的范围，包括过去41年进行的填海填海的数量，并描述变化最大的海岸线以及仍然相对原始的海岸线。这些分析使用了冲绳岛的参考地图，该地图基于从OpenStreetMap(OSM)海岸线数据集中提取的地理信息系统矢量数据(冲绳岛的平均节点距离=24米)，以及来自多个供应商的卫星和航空摄影。我们测量了431.8公里的变化海岸线，大约相当于冲绳岛海岸线总长度的63%。栖息地碎片化也是一个问题，因为剩余的自然海岸线被分成239个不同的区域(平均长度=1.05公里)。最后，该岛表面21.03公里(2)是在过去41年中填海造地的。西海岸变化最大，而东海岸处于相对较自然的条件下，特别是北部地区，拥有最多的不间断自然海岸线。鉴于沿海和海洋生态系统向亚热带岛屿当地居民提供的生态系统服务的重要性，包括旅游业带来的可观经济收入，应高度重视保护剩余的自然海岸线。
Okinawa is the largest and most populated island of the Ryukyu Archipelago in southern Japan and is renowned for its natural resources and beauty. Similar as to what has been happening in the rest of the country, Okinawa Island has been affected by an increasing amount of development and construction work. The trend has been particularly acute after reversion to Japanese sovereignty in 1972, following 27 years of post-war American administration. A coastline once characterized by extended sandy beaches surrounded by coral reefs now includes tracts delimited by seawalls, revetments, and other human-made hardening structures. Additionally, part of coastal Okinawa Island was obtained by land-filling shallow ocean areas (land reclamation). Nevertheless, the current extension of the artificial coastline, as well as the level of fragmentation of the natural coastline are unclear, due to the lack of both published studies and easily accessible and updated datasets. The aims of this research were to quantify the extension of coastline alterations in Okinawa Island, including the amount of land-filling performed over the last 41 years, and to describe the coastlines that have been altered the most as well as those that are still relatively pristine. The analyses were performed using a reference map of Okinawa Island based on GIS vector data extracted from the OpenStreetMap (OSM) coastline dataset (average node distance for Okinawa Island = 24 m), in addition to satellite and aerial photography from multiple providers. We measured 431.8 km of altered coastline, equal to about 63% of the total length of coastline in Okinawa Island. Habitat fragmentation is also an issue as the remaining natural coastline was broken into 239 distinct tracts (mean length = 1.05 km). Finally, 21.03 km(2) of the island's surface were of land reclaimed over the last 41 years. The west coast has been altered the most, while the east coast is in relatively more natural conditions, particularly the northern part, which has the largest amount of uninterrupted natural coastline. Given the importance of the ecosystem services that coastal and marine ecosystems provide to local populations of subtropical islands, including significant economic income from tourism, conservation of remaining natural coastlines should be given high priority.