Coastal areas face unprecedented challenges from accelerating sea-level rise, increasing urbanisation and biodiversity loss, necessitating sustainable coastal protection strategies that go beyond traditional engineering approaches: While Nature-based Solutions (NbS) offer ecological benefits, their implementation faces constraints in space, timely readiness and standardisation. Hybrid Nature-based Solutions (HNbS) have emerged as promising alternatives, yet current taxonomic classifications remain ambiguous and insufficient to accommodate emerging technologies. This synthetic review analyses the evolution and current role of NbS in coastal climate change adaptation through a comprehensive juxtaposition of design principles and functional mechanisms of engineered and nature-based coastal defences. The review synthesises knowledge from sustainable climate adaptation and digital fabrication literature to establish precise taxonomic classifications for solutions that integrate engineered and nature-based approaches, namely HNbS. The analysis reveals gaps in the existing HNbS taxonomy, particularly regarding structures enabled by digital fabrication technologies. The three identified, distinct categories of HNbS are: (1) Hybrid Nature-based Strategies, combining engineered and natural elements at planning scales; (2) Hybrid Nature-based Modules, integrating both components within individual structures; and (3) Confluent Hybrid Nature-based Solutions, representing an emerging category where engineering and natural systems converge at material or microorganism scales, offering distinctly engineered infrastructures with natural characteristics. While contemporary hybrid approaches are being implemented, Confluent Hybrid Nature-based Solutions under research, may face a critical timing mismatch due to a gap between lengthy innovation timelines and urgent adaptation needs. Dynamic Adaptive Policy Pathways provide a framework for strategically accommodating these emerging innovations, enabling early-stage solutions and performance demonstration under real-world conditions. The new taxonomic framework outlined in this study prevents imprecise terminology and provides a foundation for robust, low-regret coastal adaptation strategies addressing contemporary and future coastal pressures like climate change impacts and biodiversity conservation requirements.

Climate change-induced sea level rise has exacerbated coastal change putting millions of people at risk from coastal hazards, such as flooding and coastal erosion. Nature-based solutions have been recognised as an opportunity to simultaneously address the coastal hazard risks and achieve biodiversity goals. While such solutions are included in climate adaptation strategies, “hard” engineered solutions are still often preferred by those implementing the schemes. We sought to explore the diverse perspectives on UK coastal flood risk management among interested and/or affected groups by utilising the Q-methodology. We identified five perspectives: (1) The Pro-Green Practitioners; (2) The Future-Planning Relocators; (3) The Case-by-Case Thinkers; (4) The Cautious Practitioners and (5) The Climate Change Concerned. All five perspectives strongly valued the co-benefits of nature-based solutions and their role in coastal risk reduction. None of the perspectives prioritised hard-engineered solutions as the primary flood protection strategy in the UK, though they recognised their role in protecting essential infrastructure. The main disagreements between perspectives were (1) on the need for relocation strategies, and (2) whether nature-based solutions could cause social inequalities. The Q-methodology does not identify how prevalent such perspectives are, thus further research is needed to assess the social acceptance of nature-based solutions.

Climate change has been recognised as a major concern in coastal hotspots exposed to multiple climate hazards under regionally specific characteristics of vulnerability. We review the emerging research and current trends in the academic literature on coastal climate risk and adaptation from a human security perspective. The ecological and socioeconomic developments are analysed for key risk areas, including coastal infrastructure; water, food and fisheries; health; human mobility; and conflict, taking the different geographical contexts of coastal areas in islands, megacities and deltas into consideration. Compounding and cascading interactions require integrative research and policy approaches to address the growing complexity. Governance mechanisms focus on coastal management and adaptation, nature-based solutions and community-based adaptation, considering their synergies and trade-offs. This perspective allows for a holistic view on climate risks to human security and vicious circles of societal instability in coastal systems and the interconnectedness of different risk dimensions and systems necessary for sustainable and transformative adaptation solutions for the most affected coastal hotspots.