CNRS, Université de Bordeaux, UMR 5805 EPOC, 33615 Pessac CEDEX, France.
Office National des Forêts, 75570 CEDEX 12 Paris, France.
Sci Total Environ. 2021 Aug 15;782:146813. doi: 10.1016/j.scitotenv.2021.146813. Epub 2021 Apr 5.
In northern Europe, coastal dune remobilization by restoring natural processes is considered by some to maintain the coastal dune in chronically eroding sectors by migrating landward and to restore dune ecology. In wet climatic contexts, this nature-based solution has been shown to induce an increase in both sand bare areas and vegetation diversity. However, it has never been tested in the coastal dunes of southern Europe with a drier climate and, thus, more stressful conditions, where disturbance may inversely decrease vegetation diversity. An original experiment was set up in 2018 on a 4-km stretch of coastal dune in southwest France where Experimental Notches (EN) were excavated in the incipient foredune, referred to as West Experimental Notch (WEN), and in the established foredune, referred as to East Experimental Notch (EEN). Morphological and ecological responses were monitored using UAV photogrammetry and vegetation sampling along transects during two years with contrasted winter storm conditions. During the first winter characterized by calm wind conditions, a rapid filling of the WENs and the initiation of deposition lobes landward of the EENs were observed. Stronger winds during the second winter led to the development of deposition lobes of the EENs, increasing both their volume, up to 6 times, and their cross-shore elongation. The increase in disturbance induced by the notches had a significant impact on vegetation. New sandy bares were colonized by pioneer species leading to an increase in species richness and rejuvenation, in particular landward of the EENs. Although longer-term monitoring is required to draw conclusions, these results suggest that the excavation of foredune notches are able to re-establish an ecomorphological dynamic in the dunes of southwest France on the time scales of years, promoting landward sand transport and, thus, the foredune landward translation, while not threatening diversity. Such approach may become a relevant adaptation strategy to sea level rise and increased erosion in this region of the world.
在北欧，通过恢复自然过程来促使沿海沙丘重新移动，被认为可以使处于持续侵蚀状态的沿海沙丘在向陆地迁移的过程中保持稳定，并恢复沙丘生态。在湿润的气候条件下，这种基于自然的解决方案已被证明可以增加沙质裸露区域和植被多样性。然而，它从未在欧洲南部沿海沙丘进行过测试，这些沙丘气候干燥，条件更为恶劣，在这种情况下，干扰可能会反向降低植被多样性。2018 年，在法国西南部的一段 4 公里长的沿海沙丘上进行了一项原始实验，在初生的前沙丘中（称为西实验切槽 WEN）和成熟的前沙丘中（称为东实验切槽 EEN）挖出了实验切槽。利用无人机摄影测量技术和沿横断面进行的植被采样，在两年的时间里监测了形态和生态响应，期间冬季风暴条件差异较大。在第一个冬季，风平浪静，WEN 迅速被填满，EEN 前缘开始出现沉积扇。第二个冬季风更强，导致 EEN 沉积扇的发展，其体积增加了 6 倍，横向延伸也增加了。切槽增加的干扰对植被有显著影响。新的沙质裸露区域被先锋物种殖民，导致物种丰富度增加，尤其是在 EEN 前缘。尽管需要更长时间的监测才能得出结论，但这些结果表明，在法国西南部沙丘中挖掘前沙丘切槽能够在数年的时间尺度上重新建立生态形态动态，促进向陆地的沙运，从而使前沙丘向陆地迁移，同时不会威胁到多样性。这种方法可能成为该地区应对海平面上升和侵蚀增加的一种相关适应策略。
