Effects of rising temperature on the viability of an important sea turtle rookery


A warming world poses challenges for species with temperature-dependent sex determination, including sea turtles, for which warmer incubation temperatures produce female hatchlings. We combined in situ sand temperature measurements with air temperature records since 1850 and predicted warming scenarios from the Intergovernmental Panel on Climate Change to derive 250-year time series of incubation temperatures, hatchling sex ratios, and operational sex ratios for one of the largest sea turtles rookeries globally (Cape Verde Islands, Atlantic). We estimate that light-coloured beaches currently produce 70.10% females whereas dark-coloured beaches produce 93.46% females. Despite increasingly female skewed sex ratios, entire feminization of this population is not imminent. Rising temperatures increase the number of breeding females and hence the natural rate of population growth. Predicting climate warming impacts across hatchlings, male–female breeding ratios and nesting numbers provides a holistic approach to assessing the conservation concerns for sea turtles in a warming world.

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Figure 1: Cape Verde is a very important loggerhead rookery with an estimated 10,000–15,000 nests laid annually across the archipelago49,50.
Figure 2: Mean sand temperature versus mean air temperature for nesting beaches on the island of Sal.
Figure 3: Mean metabolic heating of loggerhead eggs on the island of Sal, Cape Verde.
Figure 4: A 250-year incubation temperature time series for the beaches of Sal according to the SRES A2 scenario with the 95% prediction intervals (grey lines).
Figure 5: A 250-year hatchling sex ratio time series for the light sand beaches (lower grey line), dark sand beaches (upper grey line) and all beaches combined (black line) of Sal according to the SRES A2 scenario.
Figure 6: A 250-year operational sex ratio time series (upper line) and expected change in nesting numbers (lower line) for Sal according to the SRES A2 scenario.


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G.C.H. was supported by the Climate Change Consortium for Wales (C3W). The authors thank Paolo Luschi and Mariel Murazzi for their help with the sand temperature measurements. We thank SOS Tartarugas for their support to loggerhead conservation in Cape Verde and the numerous volunteers who helped with the fieldwork. J-O.L. thanks Jean-Baptiste Laloë for his help in establishing the mathematical equation to calculate the hatchling sex ratios.

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J.C. initiated the project and completed all the field work. J.C., B.R., and A.T. compiled the data. G.C.H. conceived the manuscript. J-O.L. led the data analysis. J-O.L. and G.C.H. wrote the manuscript with contributions from all authors.

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Correspondence to Jacques-Olivier Laloë.

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Laloë, JO., Cozens, J., Renom, B. et al. Effects of rising temperature on the viability of an important sea turtle rookery. Nature Clim Change 4, 513–518 (2014). https://doi.org/10.1038/nclimate2236

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