Meandering shorelines: The potential for multi-level habitat complexity to ecologically enhance artificial coastal defences

Artificial coastal defences simplify, linearize, and homogenize the coast, leading to reduced species diversity, ecological functioning, and ecosystem services. Previous active management research has shown that greater habitat complexity at millimeter to decimeter scales increases the diversity of fauna and flora living on constructed shores, however, little is known regarding the potential effects of increasing the scale of complexity on larger marine species. Testing this experimentally is challenging, hence, as a first step, we conducted a meta-analysis on movement patterns, home ranges, and body size for a wide range of coastal marine species. We found that as mean body length of species increases, so does the distance travelled, home range, and core activity areas. To widen the variety of niches created and reduce a key negative aspect of coastal engineering, we argue that the design and planning of future coastal defences should consider incorporating more complex structures across scales from millimetres to kilometres.