Short-Term Recovery of Pilot Living Shoreline Projects for Salt Marsh Habitat in New Hampshire

Over the past 6 years, the New Hampshire (NH) Department of Environmental Services has shifted its preference for shoreline stabilization from traditional engineered shorelines (e.g., seawalls, concrete armoring) to nature-based living shoreline (LS) solutions. To improve the expectations and outcomes of future projects, we monitored three LS pilot projects in the Great Bay Estuary of NH from 2019 to 2022, estimated short-term recovery of the soil biogeochemistry, plant community, and habitat use by fauna, and documented adaptive management needs. Each LS was paired with a nearby (< 200 m) reference salt marsh and a degraded shoreline. After 4 years, halophyte cover had recovered 25–75% in the low marsh and 26–70% in the high marsh. Creation of salt marsh habitat supported similar mummichog population abundances (10–24 indiv. per trap) similar to reference marshes and substantially greater than no action control shorelines (0–1 indiv. per trap). Aerobic or mildly anaerobic reduction–oxidation potentials in the low marsh (14–302 mV) and high marsh (243–266 V) were attributed to rapid drainage of the marsh in two of the LS projects. A novel planting technique of spreading a turf with pre-installed graminoid plugs across the marsh surface at one of the sites may have jumpstarted development of anerobic soil conditions within 3 years (Low: − 192.7 ± 14.9 mV, High: − 119.0 ± 25.3 mV). Opportunistic foraging waterfowl and burial by wrack led to annual replacement replanting and seasonal wrack removal as adaptive management needs of these and future projects. LS projects in the Great Bay Estuary provide functional salt marsh habitat and improved shoreline resilience that can serve as a valuable strategy for coastal restoration.