Open SESAME: A Social-Ecological Systems framework for collaborative Adaptive Management and Engagement in coastal restoration and climate adaptation

This land is your land, this could be marsh land: Property parcel characteristics of marsh migration corridors in Rhode Island, USA

Salt marshes, critical habitats offering many ecosystem services, are threatened by development, accelerated sea level rise (SLR) and other anthropogenic stressors that are projected to worsen. As seas rise, some salt marshes can migrate inland if there is adjacent, permeable, undeveloped land available. Facilitating marsh migration is necessary for coastal resilience efforts, but extensive coastal development can make finding suitable migration corridors challenging. This work seeks to characterize changes in land use, ownership, and economic value at the property parcel level within current versus future marsh areas for the state of Rhode Island, USA. We find that most parcels currently containing salt marsh are publicly owned, whereas most adjacent parcels projected to contain new salt marsh in 2050 are privately owned. Additionally, parcels containing new marsh in 2050 have 47% higher per-hectare assessed values than parcels containing current marsh. We describe the locations and characteristics of parcels within migration corridors with the lowest per-hectare values that may be the most cost-effective for marsh conservation practitioners to protect. This study highlights the expanding land use types and landowner sets that will be involved in marsh conservation decisions, and the economic value of potential migration corridors where costly tradeoffs may be necessary to promote coastal resilience.

Laying it on thick: Ecosystem effects of sediment placement on a microtidal Rhode Island salt marsh

Heightened recognition of impacts to coastal salt marshes from sea-level rise has led to expanding interest in using thin-layer sediment placement (TLP) as an adaptation tool to enhance future marsh resilience. Building on successes and lessons learned from the Gulf and southeast U.S. coasts, projects are now underway in other regions, including New England where the effects of TLP on marsh ecosystems and processes are less clear. In this study, we report on early responses of a drowning, microtidal Rhode Island marsh (Ninigret Marsh, Charlestown, RI) to the application of a thick (10-48 cm) application of sandy dredged material and complimentary extensive adaptive management to quickly build elevation capital and enhance declining high marsh plant species. Physical changes occurred quickly. Elevation capital, rates of marsh elevation gain, and soil drainage all increased, while surface inundation, die-off areas, and surface ponding were greatly reduced. Much of the marsh revegetated within a few years, exhibiting aspects of classic successional processes leading to new expansive areas of high marsh species, although low marsh Spartina alterniflora recovered more slowly. Faunal communities, including nekton and birds, were largely unaffected by sediment placement. Overall, sediment placement provided Ninigret Marsh with an estimated 67-320 years of ambient elevation gain, increasing its resilience and likely long-term persistence. Project stakeholders intentionally aimed for the upper end of high marsh plant elevation growth ranges to build elevation capital and minimize maintenance costs, which also resulted in new migration corridors, providing pathways for future marsh expansion.