The vast majority of green sea turtles in the northern Great Barrier Reef are female because of warmer temperatures due to climate change, which influences their sex, researchers said. Scientists are concerned populations of these animals could turn almost completely female.
A recent study by the National Oceanic and Atmospheric Administration, California State University and Worldwide Fund for Nature Australia examined two genetically distinct populations of green sea turtles living in the Great Barrier Reef. The study found that a group of about 200,000 turtles living in the northern part of the reef was almost entirely female. While the southern population was 65 to 69 percent female, females in the northern group accounted for 99.1 percent of young turtles and 86.8 percent of adults.
After combining their results with temperature data, the scientists found that most sea turtle populations are living above the most suitable temperature. The northern green turtles have been producing mainly females for more than two decades and that the complete feminization of this population is possible in the near future, making it clear that climate change is threatening the survival of these populations.
Dermot O'Gorman, the chief executive of World Wildlife Fund Australia, said, “That's a very visible sign of the impact of climate change. But this is a quiet change.”
O'Gorman said more urgent action on climate change is clearly needed, adding that some conservationists have already taken practical measures, such as using shade cloth on turtle nesting beaches to lower the sand temperature, and reducing by catch in the fishing industry.
“Shade cloth can be used in certain places, but there's a limit to the scale you can do that,” he said, “Now every large male who can reproduce is going to be even more important.”
