Salt marshes protect coastal infrastructure from sea level rise and storm events associated with climate change. However, they are also vulnerable to climate change if environmental forcings overwhelm stabilizing feedbacks between marsh vegetation and the environment. For example, rapid marsh loss has occurred in regions of Chesapeake Bay and the New England coast due to edge erosion and interior drowning. However, other studies suggest that marshes are largely stable or can even increase in area due to accretion or transgression into uplands. Often, research documenting marsh response to climate change occurs at small spatial scales or is based on point measurements of marsh accretion relative to sea level rise rates. However, it is unclear whether, in the landscape context, marsh gains balance losses, thereby preserving regional marsh ecosystem services. Here, we integrate and analyze diverse spatial and time series datasets to quantify landscape-scale changes in marsh area in a Virginia barrier island system and investigate the mechanisms driving spatio-temporal differences in marsh responses to environmental forcings.
Results/Conclusions
We found that most marsh loss occurred in the barrier island zone, whereas mainland fringing and lagoon marshes were largely stable and, in some locations, increased in area due to transgression into upland forests. Rates of barrier island marsh loss increased over time and were correlated with increasing frequency of storm events. Analyses of aerial photographs and land cover change data suggest that barrier island marshes are buried by overwash during storm events. This has led to net marsh loss across the barrier island system, as overwash rates exceed rates of marsh accretion and transgression in adjacent landscape zones. These results demonstrate that scale is an important consideration when developing coastal management plans that aim to preserve salt marshes. If the goal is to maintain the ecosystem services that marshes confer regionally, management actions should be applied at the landscape scale by offsetting marsh loss in unstable regions with restoration practices aimed at stabilizing existing marshes or facilitating transgression into uplands.