Will sea turtles go extinct due to climate change?

Sea turtles may not survive – not because of a lack of food or pollution, but due to a worrying disappearance of males. Research shows that in warmer sand, almost only females hatch. The consequences of this phenomenon could be catastrophic for the sex ratio and long-term survival of these reptiles.

How does temperature affect the sex of sea turtles?

In sea turtles, sex is not determined by chromosomes, as in humans, but by the temperature at which the embryo develops in the egg. This phenomenon is known as temperature-dependent sex determination (TSD). For most sea turtle species, lower incubation temperatures (around 26–27°C) produce males, while higher temperatures (above 30°C) produce females. The threshold temperature, known as the pivotal temperature, is around 29°C – at this point, an equal number of males and females is born.

However, with global warming, more and more nesting beaches are reaching temperatures well above this threshold. The result? Populations are dominated by females, and fewer and fewer males are being born. In some areas, the percentage of females already reaches 99%.

Alarming data from the Great Barrier Reef

One of the most alarming examples of population feminization comes from studies conducted off the coast of Australia, published in the journal Endangered Species Research. In the northern part of the Great Barrier Reef, as many as 99.1% of juvenile green turtles (Chelonia mydas) are female, and the average age structure of the population is also female-dominated (86.8%). In the southern part of the reef, where conditions are cooler, the sex ratios were more balanced, with 65–69% females – which is still a significant majority.

The authors of the study, Jensen et al., report that climate models predict a 2–3°C increase in nesting beach temperatures by the end of the 21st century, which may lead to near-complete feminization of populations in many regions.

The effects of overheating – what happens to embryos?

The problem is not limited to sex. Research published in Functional Ecology shows that extreme temperatures lead to increased embryo mortality. The few that survive often have lower body mass, are physically weaker, and have lower post-hatching survival rates.

Some eggs do not develop at all, and among the embryos that do hatch, deformities are increasingly observed. This is proof that excessively high temperatures can eliminate entire generations of turtles even before they are born.

Can sea turtles adapt?

Although some marine reptile populations exhibit certain adaptive abilities – such as changing the timing of egg-laying or selecting shaded nesting sites – these are not universal. Female sea turtles are strongly tied to their hatching sites and usually return to the same beaches.

This means that shifting nesting locations toward cooler climate zones is limited. Moreover, the pace of global warming exceeds the adaptive capacity of these evolutionarily slow organisms. As researchers emphasize, changes that would normally take thousands of years would now have to occur within a few generations.

The last call to save sea turtles

In the face of growing threats, scientists are undertaking various conservation efforts. One method involves shading nests using nets or planting vegetation around nesting sites, which helps reduce incubation temperatures by several degrees.

Other approaches include relocating nests from overheated beaches to cooler areas and artificial incubation under controlled laboratory conditions. Although these actions are effective, they are also costly and require large-scale commitment.