Advances in ecological engineering and low-carbon products in designing of coastal structures

With the increasing threats posed by global climate change, artificial coastal structures remain essential to mitigate coastal erosion and flood risks in many regions worldwide. However, these structures are often criticized for introducing non-native materials that disrupt habitats and support lower biodiversity than natural rocks. Over the past three decades, eco-engineering has emerged as a solution to mitigate these impacts while maintaining their protective function. This study analyzes field and laboratory tests in the literature to identify advances in ecological engineering and low-carbon materials for the design of ecologically enhanced coastal structures. Key interventions include increasing surface complexity and heterogeneity of artificial substrates, evaluating the suitability of substrate types for biodiversity enhancement, and developing sustainable bio-enhancing concrete blends. Research highlights that incorporating surface roughness at scales from millimeters to decimeters, coupled with appropriate material selection can significantly enhance biodiversity while maintaining engineering performance. Examples of cost-effective habitat enhancement solutions include the BIOBLOCK unit ($2500 per unit), drill-core pools (€60 per pool), and artificial rock pools (€38 per pool). Concrete, especially with low-binder cements like slag cements (CEM III/B), is a suitable alternative when natural rock is unavailable. In this paper, studies are selected based on their relevance to coastal engineering practices, highlighting areas where further research is needed and offering recommendations to overcome barriers to the effective implementation and broader adoption of more sustainable and multifunctional coastal defences. Challenges include strengthening the evidence on achievable enhancements, clarifying cost-benefit analyzes, and improving data presentation for decision-making.