Few studies have focused on shoreline change on high mountainous tropical islands, whereas their low-lying coastal areas generally host most population centres and human assets. This paper contributes to filling this gap by assessing shoreline change on a remote Pacific island, Tubuai, French Polynesia. The study considers different shoreline proxies and time periods based on the 32-year (1982–2014) aerial imagery available. Over the multi-decadal timescale, the base of the beach predominantly exhibited retreat, observed along 57% of the shoreline. The stability line, which consists of the vegetation line or the base of coastal defences, depending on shoreline sections, was more resistant to coastal erosion, as 61% of the shoreline remained stable while 32% experienced retreat. At shorter timescales (i.e. for the four sub-periods considered in this study), results show high spatial-temporal variability. Clarifying the respective contributions of human activities and intense tropical cyclones to shoreline change, results show that the former had a major influence despite low population density, whereas the latter had a moderate influence. In fact, human disturbances have extensively destabilized sediment cells, which will likely exacerbate the negative impacts of future cyclones on tropical shorelines and their inhabitants. Findings provide insights for developing strategies for risk reduction in remote islands with low population densities and available space.

很少有研究集中在山区多山的热带岛屿上的海岸线变化，而其低洼的沿海地区通常拥有大多数人口中心和人力资源。本文通过评估法属波利尼西亚图布艾岛一个偏远太平洋岛上的海岸线变化，为填补这一空白做出了贡献。该研究基于可用的32年（1982年至2014年）航空影像，考虑了不同的海岸线代理和时间段。在数十年的时间尺度上，沿海岸线的57％观察到海滩的底部主要呈退缩状态。由植被线或沿海防御基础组成的稳定线（取决于海岸线部分）对海岸侵蚀更具抵抗力，因为61％的海岸线保持稳定，而32％的海岸线则退缩。在较短的时间范围内（即 （对于本研究中考虑的四个子时期），结果显示出较高的时空变异性。澄清了人类活动和强烈的热带气旋对海岸线变化的各自贡献，结果表明，尽管人口密度低，前者仍具有主要影响力，而后者则具有中等影响力。实际上，人为干扰已使沉积物细胞大大不稳定，这可能会加剧未来旋风对热带海岸线及其居民的负面影响。这些发现为制定人口密度低和可用空间较小的偏远岛屿减少风险的战略提供了见识。结果表明，尽管人口密度低，但前者的影响很大，而后者的影响中等。实际上，人为干扰已使沉积物细胞大大不稳定，这可能会加剧未来旋风对热带海岸线及其居民的负面影响。这些发现为制定人口密度低和可用空间较小的偏远岛屿减少风险的战略提供了见识。结果表明，尽管人口密度低，但前者的影响很大，而后者的影响中等。实际上，人为干扰已使沉积物细胞大大不稳定，这可能会加剧未来旋风对热带海岸线及其居民的负面影响。这些发现为制定人口密度低和可用空间较小的偏远岛屿减少风险的战略提供了见识。