Building an evidence base for living shorelines: a framework for evaluating the extent and adequacy of...

Living shorelines are increasingly promoted as a nature-based solution to the growing expense and environmental impacts of conventional engineered coastal protection structures. The coastal ecosystems used in living shorelines increase coastal resilience through wave attenuation and sediment stabilization and offer potential co-benefits such as biodiversity enhancement, productive fisheries, improved water quality and carbon sequestration. Despite the benefits of living shorelines, a suite of technical and socio-political barriers exists to their use as standard practice in coastal management. One barrier is an accessible evidence base on the technical capabilities of living shorelines that provide confidence in their application. Monitoring on-ground projects is a critical component in building the evidence base needed to inform technical guidance. However, monitoring of living shorelines remains neither standardized nor regulated, which can limit the ability to compare outcomes across projects. Here, we present a framework for evaluating the effectiveness of monitoring activities for living shorelines based on eight evaluation metrics - functional design criteria, indicators, monitoring design, sampling periodicity, sampling duration, sustainability, data availability and reporting, and management linkage. We applied this framework to 131 living shorelines projects in Australia. Monitoring activities often scored highly for projects that employed higher-cost techniques to protect valuable infrastructure and were integrated into ongoing coastal asset management programs. In contrast, some long-established techniques had limited routine monitoring data available. Emerging techniques were frequently the subject of scientific studies with robust experimental designs, but their link to management was often weaker. Not all criteria need to be fully met for a project to contribute meaningfully to the evidence base for living shorelines. The framework helps evaluate different aspects of monitoring programs and their influence on project conclusions. When applied across multiple projects, it can provide a standardized assessment of the overall strength of evidence supporting different living shoreline approaches.