SIGNATURES OF RESILIENCE IN HUMAN-ALTERED COASTAL SYSTEMS

世界上85%以上的海岸线都受到了人类活动的影响。这些活动及其后果集中在低海拔海岸带：一个海拔低于10米的沿海地带，居住着多达10亿人口，占地球物理基础设施的不成比例。低洼海岸线上如此明显的人口和基础设施暴露意味着这些环境承受着海岸灾害（例如，侵蚀、风暴潮、洪水、海平面上升）的严重影响。此外，人口增长、基础设施扩张和气候变化只会加剧灾害影响。随着沿海风险（定义为人类和基础设施暴露于自然灾害中）的增加，对沿海恢复力的广泛科学兴趣也在增加，作为传统工程方法的替代方案，以保护人类改变的海岸线免受自然灾害的影响。这里，沿海恢复力被定义为沿海系统——沿海环境的物理、生态和人类组成部分，以及维持其功能的这些组成部分之间的关系——如何随着时间的推移从干扰（如极端风暴）中恢复过来。在低海拔海岸带的临海边缘，以海滩、沙丘、洪泛平原和湿地为特征的环境从它们吸收的风暴事件中形成了它们的物理形状。许多低洼海岸线虽然不容易受到自然灾害的影响，但人类活动却在其基础上大量建设，并对其进行了剧烈的改变。然而，人类改变的海岸线几乎从未作为动态环境本身进行过研究。了解人为改变的海岸线作为动态系统对于预测灾害影响、预测气候变化的影响和减少沿海风险至关重要。以前的研究使用计算机建模表明，与自然的海岸线不同，人类改变的海岸线随着时间的推移变得越来越容易受到风暴的破坏，并且在功能上依赖于工程危险防御——因此使它们的弹性不如自然屏障。但是，人类改变的海岸线和自然海岸线如何演变的差异，以及这对它们的恢复力意味着什么，还没有通过实际地点的观察和测量来证明和检验。本项目通过用经验证据检验理论来解决这一差距。这个项目的目的是利用分析几十年卫星图像的新方法，确定和测量世界各地人类改变和自然低洼海岸环境的恢复能力指标——所有这些都在低海拔海岸带暴露的向海边缘。我将测量区分人为改变和自然海岸线的物理“特征”，将这些物理特征与沿海发展的长期模式联系起来，并结合这些信息来确定这些人为改变与自然海岸环境的相对“稳定性”。这个项目将是第一个以这种方式量化沿海复原力的项目，而且是在这种规模上，完全来自真实环境的观测数据。总体而言，该项目以人为改变的海岸线为重点，采用新颖的分析方法，将为全球脆弱的低洼沿海环境的复原力提供新的、观察驱动的见解。从这个项目中产生的方法和发现将使未来的跨学科研究能够以有针对性的、高效的、有效的方式有意识地增强沿海恢复力，以减少沿海风险。

More than 85% of the world's coastline has been somehow altered by human activities. These activities and their consequences are concentrated in the Low Elevation Coastal Zone: a ribbon of coastal land below 10 m elevation that hosts as many as 1 billion people and a disproportionate share of the planet's physical infrastructure. Such pronounced exposure of people and infrastructure along low-lying coastlines means that these environments sustain severe impacts from coastal hazards (e.g., erosion, storm surge, flooding, sea-level rise). Moreover, population growth, infrastructural expansion, and climate change only make hazard impacts worse.As coastal risk - defined as the exposure of people and infrastructure to natural hazards - has increased, so has broad scientific interest in coastal resilience, as an alternative to conventional engineering approaches to protecting human-altered coastlines from natural hazards.Here, coastal resilience is defined as how a coastal system - the physical, ecological, and human components of a coastal environment, and the relationships among those components that sustain their functioning - recovers from disturbances, like extreme storms, over time. At the seaward edge of the Low Elevation Coastal Zone, environments characterised by beaches, dunes, floodplains, and wetlands take their physical shape from the storm events that they absorb. Despite their precarity to natural hazards, many low-lying coastlines are extensively built upon and intensively altered by human activities. However, human-altered coastlines are almost never examined as dynamic environments in their own right.Understanding human-altered coastlines as dynamic systems is essential to predicting hazard impacts, anticipating effects of climate change, and reducing coastal risk. Previous work has used computer modelling to suggest that unlike their natural counterparts, human-altered coastlines evolve over time to become increasingly vulnerable to storm damage and functionally dependent on engineered hazard defences - thus rendering them less resilient than natural barriers. But that difference in how human-altered and natural coastlines evolve, and what that means for their resilience, has not yet been demonstrated and examined with observations and measurements from real places. This project addresses that gap, by testing theory with empirical evidence.The aim of this project is to identify and measure indicators of resilience in human-altered and natural low-lying coastal settings around the world - all at the exposed, seaward edge of the Low Elevation Coastal Zone - using new methods for analysing decades of satellite imagery. I will measure the physical "signatures" that distinguish human-altered from natural coastlines, relate those physical signatures to patterns of coastal development over time, and combine that information to determine the relative "stability" of these human-altered versus natural coastal settings. This project will be first to quantify coastal resilience this way, and at this scale, derived entirely from observational data from real settings.Overall, with its focus on human-altered coastlines and its novel analytical approach, this project will deliver new, observation-driven insights into resilience in vulnerable low-lying coastal environments worldwide. The methods and findings that emerge from this project will enable future interdisciplinary research into how coastal resilience could be deliberately enhanced in targeted, efficient, effective ways to reduce coastal risk.