Permanent loss of barrier island resilience due to a critical transition in dune ecosystems

Barrier islands cover a large fraction of US coasts and support unique ecosystems and coastal infrastructure. The 'barrier' function of a barrier island depends on coastal dunes that can prevent storm flooding and widespread ecosystem loss. Furthermore, dune-less barriers are more susceptible to breaching and potential drowning under sea level rise. Here we study the transition from richly-vegetated barriers with mature dunes ('high' state) to dune-less barren barriers ('barren' state) using data from a representative set of barrier islands in Virginia, US. We find that these two states are possible stable solutions of a non-linear stochastic dynamics characterized by a tipping point at which barriers with elevation around beach berms experience a critical transition into a permanently barren state. Our results suggest that frequently-flooded dune-less barren islands are a natural endpoint of barrier's evolution under sea level rise. "Barrier islands experience a critical morphodynamic transition from a high dune-rich state to a low dune-less state after reaching lower elevations, according to dune dynamics modeling based on field data from the Virginia Barrier Islands, USA".