Collaborative Research:The Role of Ecomorphodynamic Feedbacks in Barrier Island Response to Climate Change

气候变化导致的海平面上升和风暴强度的增加将影响世界各地的障碍岛。传统的堰塞岛演化观点只考虑环境条件(如海平面上升、风暴变化)和物理过程(如输沙)的变化，并预测堰塞岛将逐渐对气候变化做出反应。然而，最近的研究表明，涉及植被以及植被和物理过程之间的相互作用或反馈的生物因素在塑造岛屿和确定它们将如何应对未来不断变化的条件方面也很重要。例如，预期的气候变化引起的沙丘建造草地理范围的变化可能会改变保护沙丘的形状和高度，从而增加岛屿对风暴的脆弱性。而且，就像植被和物理过程之间的相互作用可以建造沙丘一样(通过沙丘修筑草的沙子捕捉)，它们也可以通过维持低海拔地区来阻碍甚至阻止沙丘的建造。这种反馈可能会导致环境条件的逐渐变化，从而导致障碍岛进化的快速变化，这将使人类难以适应。这个项目将使我们能够更好地了解决定屏障岛屿未来如何变化的重要过程，以及在哪些条件下重要的过程和相互作用可能导致岛屿行为的快速变化，而不是逐渐变化。该项目将检验这样一种假设，即生态形态动力学反馈有可能放大气候变化对障碍岛演变的影响，导致对强迫的逐步变化的非线性反应，即障碍岛从高度缓解、稳定、生态多样化的状态迅速转变为低缓解、快速迁徙、生态同质的状态的临界点。通过在弗吉尼亚海岸保护区(VCR)LTER未开发的屏障系统中进行综合数值模拟和生态学实验，该项目将解决关键问题，包括：植被和物理过程如何在屏障岛地形的形成和演化中相互作用？暴雨过后，洪水对地形恢复和植被定居有何影响？生态地貌动力反馈在风暴过后地形恢复中的作用是什么？由于生态地貌动力系统中的非线性，什么因素的组合导致了高缓解状态和低缓解状态之间的转变的临界点？气候变化如何改变生态地貌动力学反馈？反馈在国家之间的过渡中扮演什么角色？

Climate-change-induced sea level rise and increases in storm intensity will affect barrier islands worldwide. The traditional view of barrier island evolution considers only changes in environmental conditions (such as sea level rise, changes in storms) and physical processes (such as the transport of sand), and predicts that barrier islands will respond to climate change gradually. However, recent work suggests that biological factors involving vegetation and interactions, or feedbacks, between vegetation and physical processes are also important in shaping islands and determining how they will respond to changing conditions in the future. For example, anticipated climate-change induced shifts in the geographic ranges of dune-building grasses may increase the vulnerability of islands to storms by changing the shape and height of protective dunes. And, just as interactions between vegetation and physical processes can build dunes (via sand trapping by dune-building grasses) they can also hinder, and even prevent, dune-building by maintaining areas of low elevation. Such feedbacks may cause gradual changes in environmental conditions to produce rapid changes in barrier island evolution, which would make human adaptation difficult. This project will allow us to better understand the processes that are important in determining how barrier islands will change in the future and the conditions under which the important processes and interactions will likely lead to rapid, rather than gradual changes in island behavior. This project will test a hypothesis that ecomorphodynamic feedbacks have the potential to amplify the effects of climate change on barrier island evolution, causing a nonlinear response to gradual changes in forcing, i.e., tipping points at which barrier islands rapidly convert from a high-relief, stable, ecologically diverse state to a low-relief, rapidly migrating, ecologically homogenous state. Through integrated numerical modeling and ecological experiments in the undeveloped barrier system of the Virginia Coast Reserve (VCR) LTER this project will address critical questions including: How do vegetation and physical processes interact in the formation and evolution of barrier island topography? How do overwash events affect topographic recovery and colonization of vegetation following storms? What is the role of ecomorphodynamic feedbacks in topographic recovery following storms? What combinations of factors lead to tipping points in the transition between high-relief and low-relief states as a result of nonlinearities in the ecomorphodynamic system? How are ecomorphodynamic feedbacks altered by climate change and what is the role of feedbacks in the transition between states?