资源环境科技发展态势分析平台

Salt marsh assessments focus on vertical metrics such as accretion or lateral metrics such as open-water conversion, without exploration of how the dimensions are related. We exploited a novel geospatial data set to explore how elevation is related to the unvegetated-vegetated marsh ratio (UVVR), a lateral metric, across individual marsh "units" within four estuarine-marsh systems. We find that elevation scales consistently with the UVVR across systems, with lower elevation units demonstrating more open-water conversion and higher UVVRs. A normalized elevation-UVVR relationship converges across systems near the system-mean elevation and a UVVR of 0.1, a critical threshold identified by prior studies. This indicates that open-water conversion becomes a dominant lateral instability process at a relatively conservative elevation threshold. We then integrate the UVVR and elevation to yield lifespan estimates, which demonstrate that higher elevation marshes are more resilient to internal deterioration, with an order-of-magnitude longer lifespan than predicted for lower elevation marshes.

Plain Language Summary Salt marshes are valuable ecosystems that change in response to sea-level rise, sediment availability, storms, and other processes. Determining how salt marshes will change in the future is difficult. In this study we show that the elevation of a marsh relative to sea level is closely related to how much area it has been losing. The relationship between elevation and marsh area is the same across four large systems, and we can use these measurements to calculate how long a marsh will survive as sea-level rises. We found that the lowest marshes have a shorter lifespan than higher marshes, and these estimates can be used to help prioritize investments.