Plant-water interactions shape coastal dune evolution in a changing climate

Coastal dunes provide critical flood protection for low-lying coastal areas, raising the question whether these defenses can be maintained in a future climate. Dune development is driven by interactions between sediment transport and vegetation growth. Both processes are affected by climate, notably changes in precipitation. However, tools to assess future precipitation impacts on dune development remain limited. To address this, we coupled an ecohydrological model with a dune development model (AeoLiS) to simulate plant–water interactions and their influence on dune development. After validating the coupled model against observed dune volumes, we explored how rainfall changes affect dunes formed by planting marram grass and spontaneously forming embryo dunes. We compared dune development under extremely wet, dry, and future climate scenarios against a baseline, running 100 stochastic simulations for each. Our results show that wet conditions promote rapid vegetation growth, increasing embryonic and artificial dune volumes and crest heights. Dry conditions enhanced inland sediment transport and increased variability in development. Under future projections, embryo dune volumes increased by 2.7 % and artificial dune volumes by 0.4 %. Compared to embryo dunes, artificial dunes were more affected by extremely dry conditions, reducing the median volume by 1.6 % and crest height by 21 cm. Overall, our findings highlight rainfall as a key driver of dune-building through its control on vegetation growth, which mediates sediment trapping. Therefore, coastal management strategies aimed at dune stabilization may benefit from increased rainfall, while those that rely on active, mobile dune systems may become less effective under enhanced vegetation growth.