Global warming facilitates the nesting of the loggerhead turtle on the Mediterranean coast of Spain

The ranges of many species are shifting poleward as global warming intensifies, but this process might be less intense in philopatric species, i.e. those with the tendency to reproduce at their natal sites. Marine turtles are highly philopatric and their vulnerability to global warming is exacerbated by a life history combining delayed sexual maturity, temperature-dependent sex determination and low embryo survival at high incubation temperature. Detection of nesting events of loggerhead turtles in the Western Mediterranean Sea has increased largely during the first two decades of the 21st century, which could be a response to global warming or the result of increased sampling effort. The deployment of temperature data loggers at 52 beaches scattered along the Mediterranean coast of Spain demonstrated that sand temperature is currently high enough to allow the incubation of loggerhead turtles clutches in most Spanish beaches. However, the reconstruction of sand temperature from 1950 to 2019 revealed that thermal conditions suitable for the regular nesting of loggerhead turtles have existed in Spanish beaches only since 2010, although sporadic nesting was possible previously in exceptionally warm years. The future establishment of a self-sustained population would probably require further increases in temperature, to ensure a female-biased offspring production, but the process might be jeopardized by increased erosion and beach flooding resulting from sea level rise.