Report on estimated seagrass density (D4.4e)

Seagrasses are the main habitat for coastal marine ecosystems. They provide different services like sediment retention (and thus clearer waters), coastal protection (in front of marine storms), shelter for marine organisms, etc... Therefore, the state of the seagrasses are a convenient proxy for the state of coastal environment. Here we have analysed temperature projections for different European Islands and assessed wether the upper thermal limit of the main four foundation species would be met under different climate change scenarios. Our results suggest that noticeable seagrass losses could be expected under scenario RCP8.5 by the end of the century. In particular the losses would be concentrated in the Western Mediterranean (Balearic, Sardinia, Malta and Sicily) in which the coverage of Posidonia Oceanica would be reduced between a 14 and 35%. In the eastern Mediterranean the thermal threshold is higher as far as Posidonia has adapted to the warmer conditions, and thus is more resilient to projected warming. Although the projected reduction may seem moderate, it has to be kept in mind that the losses will be localized in the nearshore areas, so it is expected a large impact on water transparency in beach areas. Ecosystem services will be probably be less affected.