Sediment exchange across coastal barrier landscapes alters ecosystem extents

Abstract

Barrier coastlines and their associated ecosystems are rapidly changing. Barrier islands/spits, marshes, bays, and coastal forests are all thought to be intricately coupled, yet an understanding of how morphologic change in one part of the system affects the system altogether remains limited. Here we explore how sediment exchange controls the migration of different ecosystem boundaries and ecosystem extent over time using a new coupled model framework that connects components of the entire barrier landscape, from the ocean shoreface to mainland forest. In our experiments, landward barrier migration is the primary cause of back-barrier marsh loss, while periods of barrier stability can allow for recovery of back-barrier marsh extent. Although sea-level rise exerts a dominant control on the extent of most ecosystems, we unexpectedly find that, for undeveloped barriers, bay extent is largely insensitive to sea-level rise because increased landward barrier migration (bay narrowing) offsets increased marsh edge erosion (bay widening).