Nature-based coastal defence: developing the knowledge needed for wider implementation of living shorelines

Climate change and coastal urbanisation are accelerating the demand for protection against erosion and flooding (Kirezci et al., 2020). Rising sea levels and an increased frequency and/or magnitude of storm events has led to growing interest in alternative solutions to grey infrastructure (e.g., seawalls, revetments, dikes) due to unsustainable management costs (Hinkel et al., 2014) and environmental impacts (Bishop et al., 2017; Gittman et al., 2016). Living shorelines that use natural ecosystems either with ("hybrid approach") or without ("soft approach") hard stabilising structures for coastal protection may provide several benefits over traditional grey infrastructure (Bilkovic et al., 2017; Sutton-Grier et al., 2015). Topographically complex coastal ecosystems that include dunes, saltmarshes, mangroves, seagrasses and shellfish and coral reefs provide natural coastal protection through wave attenuation, depth-induced wave breaking, and sediment stabilization (Duarte et al., 2013; Narayan et al., 2016; Walles et al., 2015b). These ecosystems can adapt to changes in climate by growing or accreting at the rate of sea level rise (Rodriguez et al., 2014; Sasmito et al., 2016; Walles et al., 2015a), and self-repair after storm events (Gittman et al., 2014). Living shorelines can also provide multiple co-benefits such as supporting biodiversity and fisheries, water filtration, carbon sequestration, social amenity and cultural value (Guthrie et al., 2022; Moody et al., 2022; Smith et al., 2021; Tachas et al., 2021).