Monitoring the conservation status of sea turtle nesting sites: expert knowledge and quantitative indicators

Coastal habitats are key for many species of conservation concern, but they face increasing anthropogenic threats. Sea turtles rely on sandy beaches for egg incubation, which are increasingly degraded, leading to growing conservation issues. Disagreements on the conservation status and the required conservation actions can arise between conservationists and stakeholders due to the lack of objective evaluations. The first objective of this study is to provide a formal analysis of the potential and limitations of the most common indicators, such as anthropogenic threats and conservation measures, that are human-related. Thirty-six variables describing threats and conservation measures were scored and analyzed for 37 turtle nesting sites in five countries (Brazil, Cyprus, Greece, Türkiye and USA). Results show that monitoring the conservation status of a nesting site is challenging, especially if based only on human-related indicators or on the number of egg clutches deposited (the most common turtle-related indicator). Results highlight the importance of local community attitude and legal protection, that may interact in very different ways, as shown by examples from the five countries considered in this study. Ultimately, only turtle-related indicators can provide information on the impact of anthropogenic threats on the number and sex of hatchlings entering the sea. Therefore, the second objective of this study is to provide, in a single document, the necessary information for an effective monitoring of hatching production in relation to anthropogenic threats. To this aim, we review and propose a set of the 12 most feasible quantitative indicators of six biological variables.