Climate change resilience of a globally important sea turtle nesting population

Abstract

Few studies have looked into climate change resilience of populations of wild animals. We use a model higher vertebrate, the green sea turtle, as its life history is fundamentally affected by climatic conditions, including temperature‐dependent sex determination and obligate use of beaches subject to sea level rise (SLR). We use empirical data from a globally important population in West Africa to assess resistance to climate change within a quantitative framework. We project 200 years of primary sex ratios (1900–2100) and create a digital elevation model of the nesting beach to estimate impacts of projected SLR. Primary sex ratio is currently almost balanced, with 52% of hatchlings produced being female. Under IPCC models, we predict: (a) an increase in the proportion of females by 2100 to 76%–93%, but cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee male hatchling production; (b) IPCC SLR scenarios will lead to 33.4%–43.0% loss of the current nesting area; (c) climate change will contribute to population growth through population feminization, with 32%–64% more nesting females expected by 2120; (d) as incubation temperatures approach lethal levels, however, the population will cease growing and start to decline. Taken together with other factors (degree of foraging plasticity, rookery size and trajectory, and prevailing threats), this nesting population should resist climate change until 2100, and the availability of spatial and temporal microrefugia indicates potential for resilience to predicted impacts, through the evolution of nest site selection or changes in nesting phenology. This represents the most comprehensive assessment to date of climate change resilience of a marine reptile using the most up‐to‐date IPCC models, appraising the impacts of temperature and SLR, integrated with additional ecological and demographic parameters. We suggest this as a framework for other populations, species and taxa.

Embryonic Temperature Programs Phenotype in Reptiles

“…Studies of TSD species suggest the answer to both questions is yes. Variation in sex ratio is correlated with nest or water temperatures in nature in crocodilians, lizards, turtles, and fish (Janzen, 1994;Weisrock and Janzen, 1999;Wapstra et al, 2009;Simoncini et al, 2014;Pezaro et al, 2016;Jensen et al, 2018;Patricio et al, 2018;Honeycutt et al, 2019;Mitchell and Janzen, 2019;Tilley et al, 2019). These studies indicate that TSD is operative in nature.…”

“…In the case of biased primary sex ratios in TSD species, there are several behavioral, physiological, and evolutionary changes that could mitigate the effects of climate change. Adult females may respond via changes in nesting phenology or selection of different thermal microenvironments for their nests (Hays et al, 2017;Jensen et al, 2018;Patricio et al, 2018). Genetic variation in thermosensitivity of embryos will also play a critical role in evolutionary responses.…”

Assessing climate change associated sea‐level rise impacts on sea turtle nesting beaches using drones, photogrammetry and a novel GPS system

“…With cheap, portable, accurate and visually appealing/easily understood results, we have demonstrated it to be a viable solution for assessing the likely loss of to marine turtle nesting habitat, from which well‐informed and effective management responses to coastal squeeze (Fish et al, ), can be made. This workflow can be used for other sea turtle species and populations—as we demonstrate in Patrício, Varela, Barbosa, Broderick, Airaud, et al () and Patrício, Varela, Barbosa, Broderick, & Catry, et al (), but can also be broadly applied to any vulnerable species or coastal habitats, e.g. mangroves (Ellison, ; Spencer et al, ; Woodroffe, ), and shorebirds (Galbraith et al, ; Kane, Fletcher, Frazer, & Barbee, ; Thorne et al, ) or forecasting likely extent of oil spill contamination (Lauritsen et al, ), which require a realistic model for SLR projections.…”

Ecological vulnerability of two sea turtle species in the Gulf of Mexico: an integrated spatial approach

“…The next identified threat was variation in sea surface temperature (SST). This factor is considered to be one of the most important climatic threats affecting sea turtle populations and habitats, as it can disrupt reproductive rhythms (phenology), affect individual fitness and change spatial and temporal dis tributions (Hawkes et al 2009, Hamann et al 2013, Patrício et al 2019. Moreover, there is evidence of the impact of SST variations on the evaluated hawksbill populations (Álvarez-Acosta 2016).…”