Nature-Based Solutions (Dec 2023)
Timing of deployment does not affect the biodiversity outcomes of ecological enhancement of coastal flood defences in northern Europe
Abstract
Timing of installation is an important factor when planning the deployment of ecological enhancements to intertidal coastal and marine infrastructure. Such nature-based solutions (NbS) are increasingly used worldwide, so understanding whether the timing of deployment affects colonisation success is crucial to enhance their success and identify any ecological sensitivities that must be taken into consideration during construction. To date, none of the previous marine eco-engineering studies globally have looked specifically at timing. An unexpected COVID19 interruption in retrofitting Ecotiles designed to improve urban marine biodiversity provided a unique window of opportunity to address this research gap. We examined if time of deployment affects the early colonisation (within 18 months) success of eco-engineering enhancements. Thirty concrete tiles (Ecotiles) cast with a novel multi-scale, multi-species textured formliner were deployed on rock armour in three sites along the coast in Edinburgh, Scotland, at two different time periods (early March and late May 2020). After two settlement seasons, the colonisation success of 85% of the studied species did not vary between the times of deployment. Early colonisation success of intertidal species equalised within two settlement seasons of deployment, along with an overall increase in species richness. Crucially, these results also show that summer construction periods designed to reduce impacts on overwintering birds, do not adversely impact intertidal species during their peak (spring-summer) recruitment period in northern Europe. This novel result provides further support for widespread use of eco-engineering to enhance large coastal infrastructure projects and achieve ecological goals in northern Europe. More widely, this work contributes to the understanding of the impact of deployment timing on the success of similar NbS worldwide.
