Salt marshes sequester carbon at rates 10–50× faster than terrestrial forests — up to 250 g C/m²/yr — burying organic matter in anaerobic sediments where decomposition is slow. This "blue carbon" can remain stored for millennia.
Plant species sort by tidal inundation frequency: pioneer Salicornia (glasswort) colonizes bare mud; Spartina anglica dominates the low marsh; Aster tripolium and Limonium occupy the high marsh; rush meadows fringe the upland edge.
Saltmarsh vegetation slows tidal flow, causing sediment deposition that builds marsh elevation. This keeps pace with moderate sea level rise through a negative feedback — inundation → deposition → elevation gain.
A single hectare of salt marsh provides ~$4,000–$9,000/yr in services: storm surge buffering (attenuating wave height by 50–70% per 100m), water filtration, nursery habitat for commercially important fish, and carbon storage.