Active restoration across marine coastal habitats: focus on the Mediterranean sea

Active restoration is considered a profitable strategy to return ecosystems to their predisturbance state, in a reasonable time frame. However, ecological restoration of marine ecosystems is still in its infancy if compared to the terrestrial context. A review of 498 studies published in the last 25 years was carried out within the MERCES H2020 EU project to understand the effects of marine restoration actions across coastal habitats at global scale. Here, an overview focused on the Mediterranean Sea was carried out to identify both contextual and methodological determinants of restoration success in the basin. Results show that restoration efforts across habitats are increasing, especially in seagrasses and saltmarshes, but never approached at ecosystem level. Targets, methods, response variables and standards are still very heterogeneous. Short project duration (one-two years), small restoration areas (< 1 ha), lack of controls and knowledge of baselines are still a limit for deriving generalities. Finally, restorations rarely consider future challenges linked to global change, thus impairing long- term success stories. Marine restoration is a promising approach to counteract habitat loss in coastal areas. However, restoration science needs more robust approaches leading to the development of best practices (e.g. protocols, monitoring of the effects, reasons for failure) to be applied at spatial and temporal scales so as to answer to present and future disturbance regimes.