Invasive saltmarsh removal linked to reduced geomorphic resilience of a tidal flat

Abstract

Large‐scale removal of the invasive saltmarsh plant Spartina alterniflora has become a major restoration intervention along China's coast, yet its biogeomorphic consequences remain unclear. Using pre‐removal in situ sediment dynamics observations and five annual topographic surveys spanning removal, we show that S. alterniflora was associated with substantially weaker hydrodynamic forcing and sediment resuspension at the paired site, consistent with enhanced bed stability during energetic wave disturbance. Following removal of the upper‐intertidal marsh, erosion rapidly expanded across the mudflat system, and the profile shifted from localized, gradual adjustment to widespread, intense erosion and geomorphic reorganization. Although saltmarsh vegetation cannot eliminate vulnerability imposed by sediment limitation, it can buffer the system through energy dissipation and sediment retention. This sequence is consistent with disruption of that buffer and reduced system‐scale geomorphic resilience. These findings reveal a previously underappreciated trade‐off between invasive‐marsh management and geomorphic stability on muddy coasts.