Under a moonlit sky, turtle hatchlings emerge from the sand on Turkiye's Mediterranean coast and scramble towards the sea, taking part in an ancient natural cycle that scientists say is increasingly being shaped by climate change. Throughout the night, sea turtle biologist Yakup Kaska and his team of volunteers monitor activity in the nests.
Pyramid-shaped cages protect the eggs buried in the sand from foxes that roam the 4-km Iztuzu sandbar, a tourist beach by day and haven for turtle conservation by night. The loggerhead turtle, which nests on shores across the Mediterranean, is the mascot of COP31, the annual UN climate summit that Turkiye hosts next month.
Marine conservation will be a key focus of the gathering along the coast in Antalya. Researchers say the turtle illustrates how climate change is altering ecosystems in the Mediterranean, which has experienced a long-term warming trend since the early 1980s.
Researchers say climate change is also steadily warming nesting beaches across the Mediterranean. The sex of turtle hatchlings is determined by nest temperature.
Warming sands produce more females. "Sea turtles provide us with a very rapid warning system," said Uskudar University ecology lecturer Ayfer Sirin, who has carried out extensive research on loggerheads.
She said they reflect environmental changes affecting coastal and marine ecosystems because they depend on both land and sea. In a five-year doctoral study at Pamukkale University, Sirin found that warming temperatures were linked to earlier nesting, shorter incubation periods and a predominance of females.
The study at Patara beach estimated that on average some 70% of loggerhead hatchlings were female and concluded that behavioural adjustments alone may not be enough to offset the effects of climate change. Nest temperatures at Iztuzu rose by nearly 1℃ over the past 20 years, Kaska said, adding that broader analysis suggested females accounted for as many as 80-90% of hatchlings in many sea turtle populations.
Scientists say there is a risk that continued warming may eventually produce too few males to support successful reproduction. Another hazard is that nest temperatures above 30℃ increase the risk of embryo mortality, Sirin said.
According to the Marine Turtle Specialist Group, loggerheads are classified as vulnerable globally. Those in the Mediterranean are listed among those of least concern, reflecting conservation gains, but scientists say climate change is creating new pressures.
The turtles' migratory lifestyle illustrates the need for cross-border cooperation at COP31, Kaska said. "They might be nesting in Turkiye, but they are feeding in Tunisia or they are feeding in the Adriatic and so on," he said, calling on countries to collaborate to protect Mediterranean biodiversity.
COP31 President Murat Kurum, Turkiye's environment minister, told an Ocean and Seas conference last month: "Protecting the oceans is a responsibility we all share. We call on every party to turn that responsibility into bold, concrete action: restoring ecosystems and building resilience." Turkiye has set a goal of reaching net-zero greenhouse gas emissions by 2053 and has highlighted the expansion of renewable energy as a key element of its climate strategy.
Female loggerhead turtles typically return decades later to nest on the beaches where they hatched, but ecosystem changes mean some are struggling.