Assessment method of the sea turtle-nesting habitat of small reef islands

Abstract

The coral islets in the lagoon of New Caledonia are a major breeding and nesting site for various species. Many species reproduce and nest there, whether they are Chelonians (green turtles and loggerhead turtles), offshore seabirds (Procellariidae: shearwaters, petrels …) or more coastal (Laridae: terns, ospreys …) or sqamata (sea krait: Laticauda saintgironsi and Laticauda laticaudata). These species are dependent on the persistence of the islets in which they find the necessary conditions for nesting. Previous research has shown that these islets can evolve very rapidly at a yearly to decadal timescale. These geomorphological evolutions lead to surface area variations as well as geomorphological, topographical and land cover changes. These changes may lead to an evolution of the sea turtle nesting habitat: reduction of suitable areas for nesting and changes of the accessibility to the nesting sites. The goal of our work is to propose a method that allows to determine, map and quantify the more or less favourable character of the islets coasts to the nesting of sea turtles. Using several parameters, an indicator of the nesting attractiveness of coast is constructed and mapped. This method was applied to 13 coral islets in the southern lagoon of New Caledonia. Comparison of the results with the location of sea turtle nests acquired during the 2020 campaign attest the relevance of the method.