One of the world's largest green sea turtle colonies is shifting to an all-female population as the planet heats up, in a signal that may be repeated in other reptiles whose offspring gender is determined by temperature, a new study of the Great Barrier Reef has found.

The research, published on Tuesday in Current Biology, found more than 99 per cent of juvenile and sub-adult turtles studied at a site in the northern Great Barrier Reef are now female.

A slightly lower 86.8 per cent of adult turtles are female, indicating the gender tilt has been occurring for more than two decades.

By comparison, rates among the same green sea turtle species in the southern Great Barrier Reef are roughly two-to-one female, or close to the natural ratio.