Triggering paleo-bio-geomorphic feedbacks for nature-based delta wetland restoration

Delta wetlands persist through the capacity of vegetation and sedimentation to form self-reinforcing bio-geomorphic feedbacks, yet the strength, drivers, and global generality of these feedbacks remain poorly constrained. Here we integrate pollen-derived vegetation records and paleo-deposition data from 22 deltas across five continents to quantify vegetation–sediment feedbacks over geological timescales. Linear mixed-effects models reveal a robust, bidirectional coupling between paleo-vegetation diversity and surface deposition rates, with higher plant diversity consistently associated with enhanced sediment accretion and, reciprocally, increased deposition promoting vegetation diversification. This feedback emerges as a coherent property of delta systems globally rather than a regional anomaly. Species-level analyses identify pronounced functional heterogeneity in bio-geomorphic effects. Emergent herbaceous wetland plants, including Phragmites, Typha, and Carex, exert the strongest positive feedbacks, surpassing those of woody taxa and mangroves in regulating surface accretion. Although mangroves contribute substantially to long-term geomorphic stability, their influence on accretion rates varies across biogeographic contexts. The strength and composition of vegetation-driven feedbacks further exhibit marked continental-scale heterogeneity, reflecting differences in climate and vegetation assemblages. Together, these findings demonstrate that deltaic land-building is governed by trait-mediated paleo-bio-geomorphic feedbacks. By revealing how vegetation diversity and functional composition historically sustained sediment accretion, this study provides a process-based foundation for designing resilient, nature-based delta wetland restoration strategies under accelerating environmental change.