The key to our future lies in the past: How to integrate historical–geomorphological knowledge for future coastal decision-making?

Abstract Coastal areas that are characterized by coastal squeeze are highly vulnerable to the contemporary threats of climate change, sea level rise and biodiversity loss. Innovative coastal adaptation policies are necessary to accommodate these threats and have become salient issues on the agendas of mandated decision-makers on a global scale. This article provides a perspective on how historical–geomorphological knowledge can be integrated as an evidence base for coastal adaptation in such vulnerable zones when re-thinking and re-designing coastal adaptation policies. Our historical–geomorphological perspective proposes that we explicitly need to account for the geological, natural extent of human-modified and squeezed areas to fully understand their present-day developments. The geo-historical extent provides information on the long-term development of sedimentary structures and the functioning of coastal systems, and evaluates their effects on coastal protection, conservation and necessary adaptation. We use the Wadden Sea coastal zone as a case study to illustrate the necessity of the development of a geo-historical perspective and operationalize its integration into contemporary decision-making. The North European Wadden Sea is the largest continuous region of intertidal sand and mud flats in the world, and was recognized for its outstanding universal value by UNESCO in 2009. Nonetheless, it is an area that suffers intensely from coastal squeeze and has lost 70–80% of its coastal zone due to land reclamation and dike building. In short, our geo-historical perspective demands: (i) geo-historical risk assessment of coastal areas, (ii) geomorphological modelling that links the historical-induced risk to contemporary dynamics, (iii) assessment of ecological and societal values that are capable of estimating trade-offs between different coastal adaptation options in the contemporary system, (iv) evaluation of feasibility and legitimacy of potential coastal adaptation on the local scale of coastal inhabitants and (v) applying a transdisciplinary process that enables effective knowledge co-production between science and societal stakeholders.