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

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.