Identifying gaps in the protection of Mediterranean seagrass habitats using network-based prioritization

Abstract Aim Seagrass meadows represent a key marine ecosystem owing to the significant biodiversity they host. Protection actions are often implemented without considering connectivity between habitats. In this paper, we map and prioritize Mediterranean seagrass habitats (Posidonia oceanica and Cymodocea nodosa) based on their high potential as sources/retention of dispersal propagules or as stepping-stones. We use this information to identify gaps in the protection of highly ranked habitats. Location Mediterranean Sea Methods We use highly spatial resolved marine environmental predictors and species distribution models (SDMs) to map the seagrasses distribution. Then, we use a network-based approach to rank all predicted seagrass habitats based on their contribution to the landscape in terms of patch area (dPCintra index), potential as source/retention of propagules (dPCflux index), and stepping-stone (dPCconnector index). Finally, by overlaying our ranking with the spatial distribution of Marine Protected Areas (MPAs), we identify potential gaps in the protection of important seagrass habitats across the Mediterranean and its basins. Results Most of the identified seagrasses habitat patches are not included in MPAs, with a protection coverage exceeding half of the identified patches only in the northwestern Mediterranean. Relatively few patches contribute disproportionately to connectivity. Top ranked habitat patches are systematically excluded from the existing MPAs network, both at the Mediterranean scale and for most basins, with largest gaps for the source/sink role in the Aegean and Ionian Sea, and largest gaps for the stepping-stone role in the Adriatic, Ionian, and Tyrrenean Sea. Main conclusions Our results suggest that the current MPAs network fails to protect highly relevant seagrasses habitats in the large majority of the Mediterranean basins. However, this gap could be filled by a few well-placed MPAs. Overall, we provide novel insights for the identification of key habitats and planning novel coastal MPAs in the region.