Sea level rise threatens critical nesting sites of charismatic marine turtles in the Mediterranean

Sea level rise could result in the loss and shrinkage of coastal habitats, jeopardizing the persistence of a number of species that rely upon these highly dynamic and sensitive areas. With reproduction and population recruitment depending exclusively on low-lying sandy beaches, marine turtles are among the organisms for which sea level rise represents a major threat. Here, we provide an assessment of the potential impacts of sea level rise upon sandy beaches located at the Ionian Archipelagos, which host some of the main nesting sites of the Mediterranean population of the loggerhead marine turtle Caretta caretta. Our analyses focused on sandy beaches which host stable or sporadic nesting as well as on sites that could potentially serve as nesting grounds for the species. We demonstrated that more than 60% of the stable nesting sites (accounting for about half of the total nesting activity in the region) are likely to fail to act as nesting sites under moderate and worst case scenarios of projected sea level rise by 2100. We found that only about one fifth of the stable and the sporadic nesting beaches were characterized by high resilience to SLR, meaning that the effective zone for nesting can migrate landwards and fit in the remaining upper beach part. Potential nesting sites were subjected to even lower resilience to sea level rise, suggesting that even if marine turtles could shift to new, nearby nesting sites, the efficiency of such a response would be limited. These alarming findings call for the prioritization of conservation and restoration efforts towards sandy shores of moderate and high resilience to sea level rise which are currently used for stable or even sporadic nesting.