Abstract As global warming threatens their existence, there are widespread concerns regarding the persistence of lime-sand islands and the future of mid-ocean atoll nations. To investigate how climate change has affected lime-sand islands, changes in vegetation and other characteristics of such islands in the South China Sea (SCS) were investigated from 1989 to 2019 using 67 satellite images. First, boundaries of the lime-sand islands and their vegetation were extracted using an active contour extraction procedure called the gradient vector flow snake model. Afterwards, the spatial extents were estimated by enclosing the extracted boundaries, and the digital shoreline analysis system was used to calculate beach widths. Finally, area growth rates and speeds were used to evaluate areal changes in the lime-sand islands and their respective vegetation. Based on the estimated area growth rates, area growth speeds, and beach widths, the lime-sand islands in SCS eroded over the past three decades whereas their vegetation expanded. Further analysis suggested that direct inundation caused by sea-level rise might not be clearly identified from the satellite images. However, other climate change-related factors were most likely responsible for the observed island erosions. These factors included higher wave energy, stronger typhoon intensity and destructiveness, and accelerated coral reef degradation. In addition, the observed expansion of vegetation on the lime-sand islands was likely due to the increase in precipitation in a warming world. The results show that 1) the lime-sand islands will continue to erode whereas vegetation will continue to expand; 2) As vegetation growth is significantly inhibited by salt water when it is adjacent to the ocean, vegetation areas on lime-sand islands may start to continuously decline. Overall, this study is the first to quantitatively examine changes in SCS lime-sand islands due to global warming.

中文翻译：

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过去 30 年来南海石灰砂岛如何应对全球变暖：来自卫星遥感图像的证据

摘要 由于全球变暖威胁着它们的生存，人们普遍关注石灰砂岛的持久性和大洋中部环礁国家的未来。为了调查气候变化如何影响灰砂岛，我们使用 67 幅卫星图像调查了 1989 年至 2019 年南海（SCS）中这些岛屿的植被和其他特征的变化。首先，使用称为梯度矢量流蛇模型的活动轮廓提取程序提取灰砂岛及其植被的边界。然后，通过包围提取的边界来估计空间范围，并使用数字海岸线分析系统计算海滩宽度。最后，使用面积增长率和速度来评估石灰砂岛及其各自植被的面积变化。根据估计的面积增长率、面积增长率和海滩宽度，南海的石灰砂岛在过去 30 年中受到侵蚀，而其植被却在扩大。进一步的分析表明，从卫星图像中可能无法清楚地识别出由海平面上升引起的直接淹没。然而，其他与气候变化相关的因素很可能是造成观察到的岛屿侵蚀的原因。这些因素包括更高的波浪能、更强的台风强度和破坏性以及加速珊瑚礁退化。此外，观察到的石灰砂岛上植被的扩张可能是由于世界变暖导致降水增加。结果表明：1）灰砂岛将继续侵蚀，植被将继续扩大；2）由于临近海洋，植被生长受到盐水的明显抑制，灰砂岛上的植被面积可能会开始持续减少。总的来说，这项研究是第一个定量研究由于全球变暖导致南海石灰砂岛变化的研究。