Higher global temperatures causing Caretta turtles to lay eggs sooner

According to Archelon, this is the first time in 40 years of monitoring the turtles on Zakynthos, the Peloponnese and Crete, starting in 1984, that a nest has been found so early in the season.

Archelon volunteers and researchers monitor the breeding activities of the Caretta caretta turtles from May until October every year, beginning with preparations at their facilities and the training of the new volunteers. This year, they met with a surprise on their first visit to the beach on May 11, as the first nest of the season had already been made the previous night at Sekania, in the Zakynthos National Marine Park.

According to Dr. Aliki Panagopoulou, in charge of research for Archelon, the records of previous years confirmed that this was the first time a nest had been found in Lagana so early in the year, while the first nests in the Bay of Kyparissia and in Rethymno quickly followed, on May 15, also earlier than usual.
According to Archelon experts, scientists have been predicting that the egg-laying season will be brought forward due to climate change since 2016, as turtles are sensitive to the repercussions of higher global temperatures, both on land and in the sea. According to some researchers (Patel et al, 2016) an earlier egg-laying season may be an adaptation to help avoid the very high summer temperatures.

"Even if shifting egg laying to cooler days may offer some relief to the turtles, climate change can have a negative impact on them in other ways. For example, an increase in temperatures within nests during hatching can affect the sex of the hatched turtles. High temperatures lead to the birth of more female than male turtles, which can affect populations and their survival," Dr. Panagopoulou warned.

A recent report on the State of the Climate in Europe in 2023 published by the European Commission found that the average temperature at the surface of the sea in all European seas in 2023 was the warmest ever recorded. In the Mediterranean in July and August that year, marine heatwaves where the surface temperature was 5.5C higher than average were recorded in some areas. As the oceans have absorbed 90% of the additional heat generated by man-made greenhouse gas emissions, changes in ocean temperature could have devastating effects on marine ecosystems and wildlife.