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Climate change, fears biologists, could endanger the survival of sea turtles. Because warmer ocean temperatures disturb the balance of the sexes.

It has been known since the 1980s that the ambient temperature determines the sex of turtle embryos. Optimal conditions for a balanced ratio of female and male offspring are 29 degrees Celsius. If it is colder, more males are born - it is warmer, more females.

Scientists led by Jacques-Olivier Laloë from the University's College of Science published another finding in the Global Change Biology Journal: They examined not only the temperature effect of sexing but also the survival rate in the nest. Eggs of sea turtles develop best at 25 to 35 degrees Celsius. If it gets warmer, the embryos can not develop normally. "Up to a point, the warmer temperatures have a positive impact and allow the population to grow first, " explains Laloë. "There are more females producing more eggs. But beyond the critical point, the natural growth rate then decreases, as the nest mortality increases. "In the sea around the African island state of Cape Verde, for example, the researchers expect that nest building will take about 30 percent by the year 2100. If temperatures continue to rise, the population collapses.

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© science.de - Ruth Roebuck / Karin Schlott
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