A type of underwater plant known as Posidonia oceanica plays a crucial role in maintaining the health of Mediterranean ecosystems. Found along the coasts of the Mediterranean Sea from the surface down to 40 meters, this plant forms dense meadows that are vital for marine life. Each winter, its leaves fall to the shore, contributing to the iconic striped patterns seen on Mediterranean beaches. However, Posidonia is now under threat, largely due to damage caused by boat anchors that scrape the seabed. To address this, scientists in the Alpes-Maritimes region are conducting surveys to monitor the health of these meadows. A restoration project called Repic (Restoring impacted posidonia due to anchors) is actively working to repair damaged areas. Divers and researchers collect fragments of the plant that have been torn by anchors, place them in containers, and replant them in a grid pattern at three pilot sites: Villefranche-sur-mer, Beaulieu-sur-mer, and the Gulf of Juan. The project has successfully replanted nearly 10,000 square meters of meadow, with a survival rate of over 80%. The effort is supported by environmental agencies, funding bodies, and private companies. Posidonia oceanica, named after the Greek god Poseidon, is unique to the Mediterranean and has seen a significant decline over the past century. In France, it now covers about 80,000 hectares, a 10% reduction from a century ago. Across the entire Mediterranean, it spans about 2 million hectares, but more than 30% of this area has been lost, according to the World Wildlife Fund (WWF). These meadows are home to more than 20% of the Mediterranean’s biodiversity, serving as nurseries for fish and providing shelter for smaller species. They also offer crucial benefits to humans, such as reducing wave energy during storms, preventing beach erosion, and storing large amounts of carbon and producing oxygen. While regulations and designated anchoring zones have helped reduce damage from pleasure boats, the seabed still bears scars from past activity. The bay of Villefranche-sur-Mer was chosen as a pilot site for restoration due to its history of severe Posidonia loss. However, new challenges are emerging. Climate change, particularly marine heatwaves, is beginning to affect the plant. Although the exact impact is still unclear, scientists have observed leaves whitening during extreme heat events. A 2025 study in Scientific Reports suggests that by 2050, up to 75% of Posidonia habitats could be lost due to rising sea temperatures, though this estimate requires further research. Interestingly, Posidonia has shown resilience, surviving in waters up to 33 degrees Celsius in Tunisia, where its leaves began to whiten but not die. Researchers also note that the plant flowers every ten years in a synchronized event, which may be triggered by extreme summer heat. This flowering, last observed in 2023 during a major marine heatwave, could be a survival strategy. Restoration efforts like Repic are now considering these environmental factors, adjusting their planting depths to better withstand temperature fluctuations. Initially, replanting was done in shallower waters, but this approach had limited success, leading to a shift toward deeper, more stable areas.