Thermal heterogeneity along the migration corridors of sea turtles: Implications for climate change ecology

Abstract

Increased temperatures caused by anthropogenic climate change are becoming a major challenge for species. In particular, species that migrate over long distances are affected by altered climatic conditions at the various sites they frequent and en route. Here, we investigated whether climatic conditions experienced by sea turtles during their migration would change in the future. We focused on the post-nesting migrations of female loggerhead sea turtles (Caretta caretta) in the Mediterranean region, to explore climatic variability along four main migration corridors and their surrounding environment. We also modeled the impact of earlier onset of migration, as a potential adaptive behavioral response of Mediterranean loggerheads. We found that over the next 80 years, sea turtles will be exposed to significant increases in sea surface temperatures (SSTs) along their key migration corridors and the surrounding area (mean rate of 0.24 °C increase per decade). The projected increase in SST falls outside the range of SSTs currently reported within the examined corridors, but falls below the threshold defined as the upper thermal limit for this species. A highly variable climatic mosaic was identified within the distinct segments of the corridors. We found no evidence to support that phenological shifts might result in turtles being exposed to climatic conditions that are similar to current levels, in the future. Our outputs offer the first comprehensive spatial assessment of climatic patterns along extended areas used for the migration of sea turtles and highlight the need to quantify the relationship between altered conditions and species physiological and energetic status. This regional analysis could provide a background methodological framework for mapping and assessing spatiotemporal patterns of climatic variability along migratory areas of marine megafauna.