Comparison of beach temperatures in the nesting range of Kemp’s ridley sea turtles in the Gulf of Mexico, Mexico and USA

Rising environmental temperatures associated with climate change can adversely affect sea turtles whose hatchling sex determination is temperature-dependent. One hypothetical response of sea turtles to near-future elevated temperatures is a shift in nesting distribution to maintain suitable thermal conditions. Assessing sea turtle responses to climate warming involves evaluating (1) how temperatures will be altered, (2) a species’ capacity to respond to changes, and (3) whether responses can mitigate the impacts of warming. We evaluated sand temperatures across nesting habitat of the Critically Endangered Kemp’s ridley sea turtle Lepidochelys kempii in the western Gulf of Mexico. Most nesting now occurs on a 30 km stretch of beach in Tamaulipas, Mexico, but was historically more widely distributed. Applying conservative projections, we assessed whether a shift in the epicenter of nesting to the northern extent of the present distribution would maintain incubation temperatures below lethal levels and suitable to produce hatchlings of both sexes. Coupling temperature measurements with known impacts of temperature on the reproductive physiology of L. kempii, we predict that northern beaches will initially support the production of mixed sex ratios. However, the rapid rate of warming and long generation time for L. kempii make a shift in nesting unlikely to ultimately mitigate the effects of elevated temperatures on hatchling sex ratios and mortality. The limited thermal profile of the restricted L. kempii nesting range, and temperature-dependent sex determination, make this sea turtle particularly vulnerable to climate change. This vulnerability provides the opportunity to gain insights on strategies for the survival of thermally sensitive species in a warming world