Two species of sea turtles in Cyprus – Green and Loggerhead – are nesting earlier in response to climate change. Sea Turtles, which are natally philopatric (species that return to their birthplace to breed and nest), are doing so earlier than in previous years.
Studies show that eggs are being laid on average 6 days earlier for each 1°c rise in temperature. Extreme heat can reach lethal thresholds for eggs. Higher incubation temperatures result in a greater proportion of female hatchlings, whereas lower temperatures result in males. The turtles will need to nest 0.5 days earlier per year to sustain the current sex ratio, and 0.7 days earlier to halt hatching deaths. This poses a threat to the stability of future populations.
A study by the University of Exeter and the Society for the Protection of Turtles believes that by 2100, loggerhead turtle offspring production will have declined to dangerously low levels. If the species does not nest earlier in the season, it could have devastating impacts on the Cypriot population.
However, Professor Broderick suggests that this change in the seasonal timing of nesting may be ‘enough’ to mitigate the effects of a warming climate. This active adjustment of behaviour is perhaps an adaptation mechanism as younger members of the population lay earlier than older members. Returning females have advanced the start of nesting by 0.78 days per year since 1993.
Similar results are being revealed worldwide. For Example, a 2018 study in the Australian Great Barrier Reef highlighted the ‘feminisation’ of one population, where 99.1% of juvenile turtles from the North of the Reef were females.
However, conservation efforts combined with the shift in Sea Turtle behaviour may help current and future generations battle with various climate change scenarios. Whether these changes are enough is unknown, as further research is required to obtain a full understanding of these populations.
