Nature-based solutions for coastal dune restoration: The case study of AlgoBox in South Brittany, France

Preventing marine submersion and coastal erosion is a major challenge in the most coastal areas because of increasing vulnerability of human issues. Awareness of the decline in biodiversity and degradation of coastal ecosystems has led to emergence of nature-based solutions, more sustainable and resilient than traditional coastal engineering. On sandy coasts, the “AlgoBox” system is a sustainable ecological solution for preserving the coastline and restoring dunes, first natural barriers against waves. This tool combines the use of sand trapping fence cases with filling by algae wrack. The addition of algae to the box helps to dampen waves and provides nutrients for plants colonization, responsible for fixing sediments. In this study, we examined the “AlgoBox” effectiveness on the dune-edge erosion belt and dune regeneration on two eroded beaches in Morbihan, France. Results of regular topographic dune-beach profile and vegetation colonization processes surveys indicate that these low-cost nature-based solutions have successfully increased sediment levels and regeneration dunes. Consequently, AlgoBox have had the positive effects of (1) stabilising the coastline and preventing it from retreating during storms (2) forming an embryonic dune and (3) enriching coastal vegetation.