Meandering artificial shorelines and their potential to enhance biodiversityHabitat Restoration, Rehabilitation & Enhancement

Peter A. Todd¹, Janine Ledet¹, Kingsley J. Griffin¹, Yan Le Su¹

¹National University of Singapore, Singapore

Climate change has increased shoreline degradation, erosion, and inundation rates globally. This, together with urbanisation, has led to the acceleration of hard coastal modifications, such as the construction of coastal defences to protect shorelines, especially in urban areas. These hard engineered structures simplify, linearize, and homogenize the coast, leading to reduced biodiversity, ecological functioning, and ecosystem services. Conversely, increasing habitat complexity can lead to greater species richness. To date, efforts to actively manipulate and enhance habitat complexity have been restricted to relatively small scales (centimetres to meters), although there are some larger examples. Natural shorelines, however, are complex at multiple scales to the extent that their length is notoriously difficult to measure due to their fractal characteristics. Artificial coastal defences that integrate complex structures across scales from millimeters to 100s of meters will widen the variety of niches created. This ‘meandering shoreline’ concept also replicates bays, headlands, reefs, and estuaries. To better understand the potential benefits of multi-scale complexity, we conducted two studies: 1. A meta-analysis on movement patterns, home ranges, and body size for a wide range of coastal marine species, and 2. A comparison of species richness between artificial hard defences with and without sandy bays. We found that, as mean body length of species increases, so does the general distance travelled, home range and core activity areas. We also found greater species richness in artificial shores that featured bays. These findings suggest that the design and planning of future coastal defences should consider incorporating habitat complexity across multiple scales to encourage colonisation and use by a wider range of species, thus reducing a key negative aspect of coastal infrastructure.