Hybrid nature–infrastructure adaptation shapes multidecadal mangrove–shoreline dynamics in a tropical delta

Coastal deltas are among the most vulnerable ecosystems to sea-level rise, sediment deprivation, and human intervention, threatening both ecological stability and millions of lives. Ensuring their long-term sustainability requires understanding how natural ecosystems interact with engineered infrastructure to shape shoreline resilience. Here, we analyse 36 years (1988–2023) of satellite-derived shoreline positions, mangrove vegetation index, and suspended sediment concentration index along the Vietnamese Southern Coastline, a critical and densely populated deltaic region. Using Geographically Weighted Regression and spatial hotspot analysis, we reveal that mangrove–shoreline relationships are highly non-stationary and context-dependent. In areas experiencing sustained sediment deposition, mangrove expansion is positively associated with shoreline progradation. However, in sediment-starved or erosion-prone zones, artificial dykes maintain shoreline stability and support mangrove persistence even in the absence of natural sediment inputs. These findings refine the assumption that sediment availability is the sole driver of mangrove distribution and highlight the interacting influence of ecological and engineered factors on coastal change. Our spatial analysis provides a transferable approach for analysing mangrove–shoreline–sediment interactions in deltaic systems under climate and development pressures. By integrating ecological and engineered responses, we offer practical insights for achieving sustainable, locally tailored adaptation in rapidly changing coastal zones. Shoreline stability in sediment-limited deltas can depend as much on engineered dykes as on natural sediment supply, according to an analysis that uses 36 years of satellite-derived shoreline, mangrove, and sediment data, combined with spatial modelling