Mediterranean coasts are projected as one of the most vulnerable areas to climatic and anthropogenic changes, mainly due to the ever-increasing relative sea level and human population. Among the most pressing questions related to these threats is how the coastal biodiversity will be impacted. Coastal wetland-based archives have an exceptional scientific potential to observe past biodiversity changes and identify key thresholds for particular ecosystems facing relative sea-level rise. Using fossil insects as main bioindicator to reconstruct the biodiversity and habitat changes, supplemented by pollen and geochemical data, I will present the long-term environmental history of two Corsican coastal wetlands located in different contexts: one on a low-laying island and the other on a deltaic floodplain. The two sites show contrasted ecosystem trajectories, and the results demonstrate the influence of the geomorphological context and land-use in the responses of these wetlands to Holocene relative sea-level rise.