The BioGeo Ecotile: Improving biodiversity on coastal defences using a multiscale, multispecies eco-engineering design

Abstract

Hard coastal defences support lower biodiversity than natural rocky shores. Ecological enhancement on coastal structures can improve biodiversity by increasing habitat heterogeneity. Most studies have investigated the effect of only one type of texture on intertidal biodiversity. There is a lack of eco-engineering designs that mimic the complexity of natural rocky shores and are scalable for real world applications and commercial manufacturing. To address these gaps, we developed a novel, multiscale (mm-cm), multispecies design called BioGeo Ecotile that is scalable and readily manufacturable. The hybrid design combines previously tested eco-engineering features (pits, holes, grooves and crevices), providing habitats for a range of intertidal organisms. To test the success of the design, Ecotiles and smooth tiles were deployed on rock armour and flood walls along Edinburgh's coast, Scotland. Post-deployment, data on species presence and abundance were collected at the start and end of the second settlement season. Textured Ecotiles supported higher species richness (F3,55 = 21.18, p < 0.001) and colonisation than smooth tiles and adjacent rock armour. Ecotiles supported more mobile species, some of which (crabs) were not recorded on the other treatments. Material type (concrete vs rock) significantly affected community composition, where concrete was dominated by fucoids and rock by barnacles. In this temperate setting, the Ecotiles have enhanced biodiversity of rock armour achieving practical conservation goals. This is the first known retrofit of tiles onto rock armour in the UK. The tiles can be scaled up to whole walls or rock armour units. We demonstrate that a science-design approach can achieve ecological and engineering goals simultaneously, which can accelerate widespread implementation of eco-engineering in large-scale projects.