Coastal Dynamics and Adaptation to Uncertain Sea Level Rise: Optimal Portfolios for Salt Marsh Migration

The sustainability of dynamic natural systems often depends on their capacity to adapt to uncertain climate-related changes, where different management options may be combined to facilitate this adaptation. Salt marshes exemplify such a system. Marsh sustainability under rapid sea level rise requires the preservation of transgression zones - undeveloped uplands onto which marshes migrate. Whether these uplands eventually become marsh depends on uncertain sea level rise and natural dynamics that determine migration onto different land types. Under conditions such as these, systematically diversi ed management actions likely outperform ad hoc or non-diversi ed alternatives. This paper develops the first adaptation portfolio model designed to optimize the bene fits of a migrating coastal resource. Results are illustrated using a case study of marsh conservation in Virginia, USA. Results suggest that models of this type can enhance adaptation benefits beyond those available via current approaches.