Bio-physical linkages in coastal wetlands – implications for coastal protection

Coastal wetlands have, for many decades, fascinated ecologists and geomorphologists alike. The existence of terrestrial vegetation communities in highly saline and hydraulically extremely dynamic environments has provided an ideal opportunity to study both ecological adaptation mechanisms to physical stressors as well as the importance of vegetation to landform evolution. In recent years, however, the importance of understanding the linkages between the biological and physical factors that control coastal wetland functioning and evolution has been brought into focus within the conservation, engineering, and policy sector. This is largely the result of a rising awareness of the value of coastal wetlands resulting from the services they provide to society. Those services include their role as natural sea defenses, a role that is becoming increasingly significant in the context of ever increasing coastal population densities alongside environmental pressures (e.g. sea level rise and increasing storm frequencies) arising from climate change. This paper reviews how, over the past quarter of a century, advances in field, laboratory, and numerical modeling approaches have made particular inroads into the quantification of the sea defense role of coastal wetlands. It is becoming increasingly clear that the sea defense function itself is complex and highly context dependent. Although there is now an urgent need for improved ecologicallyinformed engineering solutions, these are unlikely to be successful without future research finding appropriate ways of scaling up hydraulically important parameters to the landscape scale and defining the physical and biological process thresholds that control the continued provisioning of the sea defense function of coastal wetlands in the face of potential extreme events and sea level rise.