The Green Turtle populations in the northern Great Barrier Reef are turning female - due to increased water temperatures.
The rising ocean temperatures cause warmer incubation which leads to more female hatchlings being born, says a study published on Tuesday in the Current Biology journal. More than 99 per cent of eggs produce females off spring now.
"Finding that there are next to no males among young northern Green Turtles should ring alarm bells," WWF Australia chief executive officer Dermot O'Gorman said.
Scientists believe the northern Great Barrier Reef rookeries have been producing primarily females for more than two decades.
Green Turtles on the southern Great Barrier Reef were less female-biased with 65 to 69 per cent originating from the cooler rookeries.
Mr O'Gorman agreed "all is not lost" for the Green Turtle and scientists could find ways to lower nest temperatures., including by installing shade cloths.