Tidal reinstatement of coastal wetlands: a global review

Abstract Introduction Coastal wetland restoration is a global priority due to its critical role in enhancing climate resilience and biodiversity. Tidal reinstatement, through the removal or modification of tidal barriers, is a promising method to restore these ecosystems. Yet, despite growing policy attention and market incentives, a systematic understanding of implementation patterns, motivations, and outcomes remains limited. Objective This study synthesizes global evidence on tidal reinstatement to characterize its implementation and outcomes over time. Methods We conducted a systematic global review of peer‐reviewed and gray literature, compiling project‐level attributes on location, ecosystem type, scale, barrier types, management actions, project objectives, and reported responses. Results We identified 93 tidal reinstatement projects across 12 countries, predominantly in the United States (67%). Most projects targeted saltmarsh ecosystems and were less than 100 ha in size. Early restoration efforts in the 1950s focused on removing or lowering hard barriers, whereas projects since the 1990s have increasingly incorporated eco‐engineering solutions, channel modifications, and flow management. Unplanned reinstatement associated with aging or failing infrastructure is increasingly common. Project motivations have diversified over time, expanding beyond wetland function to include biodiversity conservation, pest control, support for threatened species, and human well‐being. Reported outcomes were mostly positive, with 57% of studies documenting biodiversity gains alongside improvements in hydrology, sediment dynamics, and nutrient cycling. Conclusion Tidal reinstatement is an increasingly used passive restoration approach, but evidence remains geographically clustered, ecosystem‐specific, and inconsistently monitored.