Boat anchoring pressure on coastal seabed: quantification and bias estimation using AIS data

International audience(150 words) Global shipping is economically important, but has many adverse environmental effects. Anchoring contributes greatly to this adverse impact, as it is responsible for mechanical disturbance of highly sensitive marine habitats. Recovery of these ecosystems is limited by slow regrowth. Anchoring pressure on coastal seabed habitats was estimated using AIS (Automatic Identification System) data along 1800 km of Mediterranean coastline between 2010 and 2015. A comparison with field observations showed that these results were most consistent for large boats (> 50 m). An analysis of AIS data coupled with a seabed map showed that around 30 % of the habitats between 0 and-80 m exhibited anchoring pressure. Posidonia oceanica seagrass beds were the most impacted habitat in terms of duration. This methodology efficiently estimates spatial and temporal anchoring pressure principally due to large boats and should interest managers of marine protected areas as much as coastline managers