Some 640,000 turtle hatchlings are thriving on the Great Barrier Reef thanks to a five-year recovery project on Raine Island.

Environmentalists feared the globally endangered northern green turtle would soon be extinct.

The population was dropping due to nests flooding and fewer hatchlings surviving harsh tides.

The small coral cay can be spotted on the northern tip of the Great Barrier Reef and it's where 90 per cent of the reef's entire green turtle population comes from.

Traditional owners, the Queensland Park and Wildlife Service and Great Barrier Marine Park Authority have been working together to save almost 700 turtle mothers.

It's hoped millions more hatchlings will emerge on the island over the next decade, creating a stable future for the island's vital ecosystem.