Constance Annabelle, Bunbury Nancy, Lack Natalie, Nebiker Stephan, Obura David, Fleischer-Dogley Frauke, Schaepman-Strub Gabriela
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
Seychelles Islands Foundation, P.O. Box 853, Mahé, VIC, Seychelles.
Sci Rep. 2024 Nov 22;14(1):28970. doi: 10.1038/s41598-024-74595-y.
Atolls are at risk of losing their ability to physically adapt due to rising sea levels and coral reefs' reduced sediment supply, resulting in faster erosion of reef islands. This research examines Aldabra, a raised atoll and UNESCO World Heritage Site in the Indian Ocean with diverse coastal ecosystems, to track shoreline changes against a regional sea level rise of 2-3 mm yr. Aerial and satellite images in 1960 and 2011 were used to study 85% of the atoll's shoreline through a Digital Shoreline Analysis System. Over 51 years, 61% of the shoreline remained unchanged, while 24% changed at an average rate of 0.25 ± 0.36 m yr, a low rate compared to global atoll changes. Among the areas that did change, rates of accretion and erosion in absolute values were nearly balanced and affected similar percentages (12%) of the shoreline. However, localized changes were pronounced: for example, part of the lagoon shoreline transformed from a sandy beach to a mangrove habitat, accreting by 214 m over the period. Erosion occurred at crucial turtle nesting sites and the research station. The lagoon shoreline underwent more rapid changes than the erosion-resistant ocean shoreline, particularly in areas exposed to wind and waves. Despite its dynamic shoreline, Aldabra maintained its net shoreline and likely total land area over the past 51 years, akin to other Indo-Pacific atolls-underscoring its adaptive capacity. Our research suggests that current knowledge of geomorphological processes of low reef islands is transferable to the raised Aldabra Atoll, reconfirming similar mechanisms of island-building processes at the island crest. These insights highlight an urgent need to minimize local impacts on sediment availability and transfer that might alter the natural dynamics of the shoreline of reef islands and hence limit adaptation potential. Ongoing shoreline monitoring will remain crucial for informing timely adaptation strategies for the conservation of Aldabra's unique ecosystem.
由于海平面上升以及珊瑚礁沉积物供应减少，环礁面临失去物理适应能力的风险，导致珊瑚礁岛屿侵蚀加快。本研究以印度洋上一个隆起的环礁——阿尔达布拉为例，它是联合国教科文组织世界遗产地，拥有多样的海岸生态系统，旨在追踪其海岸线变化情况，以应对区域海平面每年上升2 - 3毫米的趋势。利用1960年和2011年的航空和卫星图像，通过数字海岸线分析系统对该环礁85%的海岸线进行了研究。在51年的时间里，61%的海岸线保持不变，而24%的海岸线平均变化速率为每年0.25±0.36米，与全球环礁变化相比，这一速率较低。在确实发生变化的区域中，绝对数值上的堆积和侵蚀速率几乎平衡，且影响的海岸线比例相近（均为12%）。然而，局部变化较为显著：例如，环礁湖部分海岸线从沙滩转变为红树林栖息地，在此期间增长了214米。关键的海龟筑巢地点和研究站出现了侵蚀现象。环礁湖海岸线的变化比抗侵蚀的海洋海岸线更为迅速，尤其是在遭受风浪影响的区域。尽管其海岸线动态变化，但在过去51年里，阿尔达布拉保持了其净海岸线以及可能的总陆地面积，这与其他印度 - 太平洋环礁类似，凸显了其适应能力。我们的研究表明，目前关于低珊瑚礁岛屿地貌过程的知识可应用于隆起的阿尔达布拉环礁，再次证实了岛屿顶部类似的造岛过程机制。这些见解凸显了迫切需要尽量减少对沉积物可用性和转移的局部影响，因为这可能改变珊瑚礁岛屿海岸线的自然动态，从而限制适应潜力。持续的海岸线监测对于为保护阿尔达布拉独特生态系统制定及时的适应策略仍至关重要。
