Tidal Regulation of Lateral Fluxes Shapes Coastal Meta-Ecosystem Responses to Sea-Level Rise

Le résumé fourni par la source

Abstract Coastal tidal wetlands provide critical ecosystem services and act as natural buffers against climate change impacts, yet they are increasingly threatened by sea-level rise (SLR). Lateral fluxes across the terrestrial–aquatic interface link vertical and horizontal ecosystem dynamics and play an important role in shaping wetland elevation, connectivity, and resilience. Here, we present a global synthesis of bidirectional lateral fluxes using data from 250 surface elevation table–marker horizon (SET–MH) monitoring stations across 20 countries. Lateral fluxes were quantified using a proxy defined as the difference between sediment accretion and elevation change, capturing net source–sink dynamics within the tidal frame. We show that tidal characteristics exhibit strong nonlinear associations with lateral fluxes, with intermediate tidal amplitudes (~272 cm) corresponding to the highest net lateral exports, while tidal duration and frequency show contrasting relationships with flux magnitude. Spatial connectivity, evaluated using elevation capital as a proxy, generally increases with tidal amplitude, with macrotidal systems (>4 m) exhibiting more stable elevations (NEC > 0.5) compared to more variable and potentially vulnerable microtidal systems. Elevation gains are not solely explained by vertical accretion but are also associated with lateral contributions within the tidal frame. However, because lateral fluxes and spatial connectivity are inferred from proxy-based metrics derived from SET–MH observations, these relationships should be interpreted with caution. Overall, our results highlight large-scale linkages between tidal dynamics, lateral flux proxies, and elevation stability, providing a process-informed and globally scalable framework for understanding and predicting intertidal wetland responses under accelerating SLR.

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