DataSheet_1_Undeveloped and developed phases in the centennial evolution of a barrier-marsh-lagoon system: The case of Long Beach Island, New Jersey.docx

Barrier islands and their associated backbarrier environments protect mainland population centers and infrastructure from storm impacts, support biodiversity, and provide long-term carbon storage, among other ecosystem services. Despite their socio-economic and ecological importance, the response of coupled barrier-marsh-lagoon environments to sea-level rise is poorly understood. Undeveloped barrier-marsh-lagoon systems typically respond to sea-level rise through the process of landward migration, driven by storm overwash and landward mainland marsh expansion. Such response, however, can be affected by human development and engineering activities such as lagoon dredging and shoreline stabilization. To better understand the difference in the response between developed and undeveloped barrier-marsh-lagoon environments to sea-level rise, we perform a local morphologic analysis that describes the evolution of Long Beach Island (LBI), New Jersey, over the last 182 years. We find that between 1840 and 1934 the LBI system experienced landward migration of all five boundaries, including 171 meters of shoreline retreat. Between the 1920s and 1950s, however, there was a significant shift in system behavior that coincided with the onset of groin construction, which was enhanced by beach nourishment and lagoon dredging practices. From 1934 to 2022 the LBI system experienced ~22 meters of shoreline progradation and a rapid decline in marsh platform extent. Additionally, we extend a morphodynamic model to describe the evolution of the system in terms of five geomorphic boundaries: the ocean shoreline and backbarrier-marsh interface, the seaward and landward lagoon-marsh boundaries, and the landward limit of the inland marsh. We couple this numerical modeling effort with the map analysis during the undeveloped phase of LBI evolution, between 1840 and 1934. Despite its simplicity, the modeling framework can describe the average cross-shore evolution of the barrier-marsh-lagoon system during this period without accounting for human landscape modifications, supporting the premise that natural processes were the key drivers of morphological change. Overall, these results suggest that anthropogenic effects have played a major role in the evolution of LBI over the past century by altering overwash fluxes and marsh-lagoon geometry; this is likely the case for other barrier-marsh-lagoon environments around the world.

障壁岛（barrier islands）及其相关的障壁后环境（backbarrier environments）能够保护大陆人口聚居区与基础设施免受风暴侵袭，维持生物多样性，并提供长期碳封存等诸多生态系统服务。尽管其社会经济与生态价值举足轻重，但耦合型障壁-沼泽-潟湖环境对海平面上升的响应机制仍鲜为人知。未受开发的障壁-沼泽-潟湖系统通常会在风暴越流（storm overwash）与大陆沼泽向陆扩张的驱动下，通过向陆迁移的过程响应海平面上升。然而，这类响应可能会受到人类开发与工程活动的影响，例如潟湖疏浚（lagoon dredging）与岸线加固工程。为更深入理解开发与未开发障壁-沼泽-潟湖环境对海平面上升的响应差异，我们开展了一项局地地貌学分析，刻画了新泽西州长滩岛（Long Beach Island, LBI）过去182年的演化历程。研究发现，1840年至1934年间，LBI系统的全部五类边界均发生了向陆迁移，其中岸线后退达171米。但在20世纪20年代至50年代之间，系统行为出现了显著转变，这与丁坝（groin）建设的启动时间相吻合，而海滩养护（beach nourishment）与潟湖疏浚进一步加剧了这一转变。1934年至2022年间，LBI系统的岸线发生了约22米的进积（progradation），且沼泽平台面积快速缩减。此外，我们拓展了一个地貌动力学模型（morphodynamic model），从五类地貌边界的视角刻画了该系统的演化过程：分别为海洋岸线与障壁后-沼泽界面、潟湖沼泽向海与向陆边界，以及内陆沼泽的向陆极限。我们将该数值模拟工作与1840年至1934年LBI演化的未开发阶段的地图分析相结合。尽管该模型框架较为简化，但它能够在未考虑人类景观改造的情况下，还原该时期障壁-沼泽-潟湖系统的平均跨岸演化过程，佐证了自然过程是地貌变化核心驱动因素的前提。总体而言，这些结果表明，人类活动通过改变越流通量与沼泽-潟湖几何形态，在过去一个世纪的LBI演化中发挥了关键作用；这一结论大概率适用于全球其他障壁-沼泽-潟湖环境。