Bridging the gap between coastal engineering and nature conservation? A review of coastal ecosystems as nature-based solutions for coastal protection

Under the umbrella term of Nature-based Solutions (NbS) fall measures from a wide range of disciplines. With regard to coastal protection, coastal ecosystems represent possible and promising NbS to coastal threats such as storm surges or erosion. Around the globe, the looming climate change and related developments in the coastal landscapes as well as a paradigm shift in societal views shifted the focus of decision-makers and researchers onto NbS for coastal protection, driving the need for a comprehensive up-to-date review of coastal ecosystems like salt marshes, mangroves, seagrass meadows, beaches, dunes, coral, and shellfish/oyster reefs and their benefits for Water, Nature and People alike. While existing reviews of NbS have mainly focused on the idea of softer coastal protection in general and constraints regarding management and regulations, this study reviews not only the characteristics, features and needs of the coastal ecosystems under consideration but also examines the ecosystems' potential and related processes for coastal protection, their ecological as well as their societal benefits. This review paper is based on an extensive literature review and analysis of scientific publications, books and book sections, guidelines, reports, policy recommendations and strategies. In order to create a basis for the selection of site-suitable adaptation measures for local coastal challenges and questions, this study compiles the coastal ecosystems' key features and elaborates the provided ecosystem services for protective, ecological and societal needs. The highlighted diversity of processes within ecosystems that directly cause or support coastal protection, in combination with the multiple ecological services and societal benefits, underlines the great potential of coastal ecosystems to bridge the gap between coastal engineering and nature conservation. In combination with existing coastal protection, coastal ecosystems as NbS can serve both disciplines equally and provide an integral, sustainable element in the adaptation of coastal protection to climate change.