Optimal wave reflection as a mechanism for seagrass self-organization

`Ecosystems threatened by climate change can boost their resilience by developing spatial patterns. Spatially regular patterns in wave-exposed seagrass meadows are attributed to self-organization, yet the underlying mechanisms are not well understood. Here, we show that these patterns can emerge from feedbacks between wave reflection and seagrass-induced bedform growth. We derive coupled equations for surface waves propagating over a growing seagrass bed. Wave-induced bed shear stress shapes bedforms which, in turn, trigger wave reflection. Numerical simulations show that seagrass patterns develop once wave forcing exceeds a critical amplitude. In line with field observations, these patterns have half the wavelength of the forcing waves. Our results reveal that pattern formation optimizes the potential of a seagrass meadow to reflect wave energy, providing a clear hypothesis for future field campaigns. This implies that wave-reflecting pattern formation increases ecosystem resilience under globally intensifying wave climates. These ecosystems may inspire nature-based coastal protection measures.