Virginia Commonwealth University, Richmond, Virginia.
Norfolk State University, Norfolk, Virginia.
Glob Chang Biol. 2019 Jul;25(7):2419-2430. doi: 10.1111/gcb.14635. Epub 2019 May 11.
Due to their position at the land-sea interface, barrier islands are vulnerable to both oceanic and atmospheric climate change-related drivers. In response to relative sea-level rise, barrier islands tend to migrate landward via overwash processes which deposit sediment onto the backbarrier marsh, thus maintaining elevation above sea level. In this paper, we assess the importance of interior upland vegetation and sediment transport (from upland to marsh) on the movement of the marsh-upland boundary in a transgressive barrier system along the mid-Atlantic Coast. We hypothesize that recent woody expansion is altering the rate of marsh to upland conversion. Using Landsat imagery over a 32 year time period (1984-2016), we quantify transitions between land cover (bare, grassland, woody vegetation, and marsh) and the marsh-upland boundary. We find that the Virginia Barrier Islands have both gains and losses in backbarrier marsh and upland, with 19% net loss from the system during the timeframe of the study and increased variance in marsh to upland conversion. This is consistent with recent work indicating a shift toward increasing rates of landward barrier island migration. Despite a net loss of upland area, macroclimatic winter warming resulted in 41% increase in woody vegetation in protected, low-elevation areas, introducing new ecological scenarios that increase resistance to sediment movement from upland to marsh. Our analysis demonstrates how the interplay between elevation and interior island vegetative cover influences landward migration of the boundary between upland and marsh (a previously underappreciated indicator that an island is migrating), and thus, the importance of including ecological processes in the island interior into coastal modeling of barrier island migration and sediment movement across the barrier landscape.
由于处于陆海交界地带，堤道岛容易受到海洋和大气气候变化相关因素的影响。为了应对海平面上升，堤道岛往往通过漫滩过程向陆地迁移，在背滩沼泽上沉积泥沙，从而保持海拔高于海平面。在本文中，我们评估了内陆高地植被和沉积物输运（从高地到沼泽）对大西洋中部过渡性堤道系统中沼泽-高地边界移动的重要性。我们假设最近的木本植物扩张正在改变沼泽向高地转化的速度。我们使用 32 年的陆地卫星图像（1984-2016 年），定量分析了土地覆盖（裸地、草地、木本植被和沼泽）和沼泽-高地边界之间的转换。我们发现，弗吉尼亚堤道群岛的背滩沼泽和高地都有增加和减少，在研究期间，该系统的净损失为 19%，沼泽向高地转化的方差增加。这与最近的研究结果一致，表明向陆地迁移的堤道岛迁移速度有所增加。尽管高地面积净损失，但宏观气候冬季变暖导致受保护的低海拔地区木本植被增加了 41%，这带来了新的生态情景，增加了高地向沼泽输送泥沙的阻力。我们的分析表明，海拔和岛内植被覆盖之间的相互作用如何影响高地和沼泽之间边界的陆地迁移（这是一个以前被低估的岛屿正在迁移的指标），因此，将岛屿内部的生态过程纳入到海岸堤道岛迁移和跨越堤道景观的泥沙运动的沿海建模中是很重要的。
