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One green and two hawksbill turtle hatchlings making their way to the ocean, Milman Island, Queensland © WWF-Aus / Christine Hof

One green and two hawksbill turtle hatchlings making their way to the ocean, Milman Island, Queensland © WWF-Aus / Christine Hof

Green turtles and climate change

Recent research has revealed that the northern Great Barrier Reef’s green sea turtle offspring are born almost completely female, with males outnumbered by at least 116 to 1. If this feminisation trend continues, it will be detrimental to the future of the species. So, why is this happening? 



The sex of a sea turtle is determined by the temperature of sand incubating the eggs. Warmer temperatures, of 29.1 degrees Celsius and above produce females, and cooler temperatures produce males.

Increasing temperatures as a result of climate change means more females are born, disturbing the natural gender ratio. It’s possible that the population of sea turtles could be completely female in the near future.

This is of critical concern to the longevity for many marine turtle species. Without males, the species cannot reproduce, and the combination of this with other threats such as poaching, fishing bycatch and loss of habitat, means we are at risk of losing these majestic mariners forever.


What are we doing?


The support of Koala has allowed us to work with partners including the University of Queensland, the Queensland Department of Environment and Science and the Sea Turtle Foundation to launch a new research project to trial practical methods to cool the sand temperature of sea turtle nests.


Over three months, a range of cooling methods were trialled on Milman Island nesting beach in the northern Great Barrier Reef for both hawksbill and green turtles. These included natural shade from palm fronds and pandanus leaves, artificial shade, seawater irrigation and rainwater.

After months of trials and research analysis, the results are in!


Shading and irrigation have shown to be successful in cooling nests and producing more male hatchlings. Hatchlings from shaded nests were also faster and more active, which means they have a greater chance of survival 48 hours after emerging from their nests.


While Milman Island does not yet have a feminisation problem it offers ideal conditions to trial methods to cool nests. Through this research WWF-Australia aims to find the best method to re-establish a more natural gender ratio and which can be scaled up for use in remote areas and on Raine Island, the largest green turtle rookery in the world.

A green turtle (Chelonia mydas) swimming in the Great Barrier Reef, Queensland © Troy Mayne

Working together to make an impact

Through meaningful partnerships we are able to work on projects like these that trial innovative methods to safeguard the future of species impacted by climate change.
Thank you to our partners Koala, the University of Queensland, Department of Environment and Science and the Sea Turtle Foundation for making this project possible.
Hawksbill turtle on Milman Island - ©WWF-Australia / Veronica Joseph

© WWF-Australia / Veronica Joseph

Timeline of project

January 2019: Egg laying begins and trialling of cooling and shading methods including natural and artificial shading and irrigation systems.
March 2019: Turtles hatch. Performance test to be conducted on turtles to analyse differences in movements between hatchlings that were shaded and those that were not.
August: 2019: Results of trial. The solution is shade!
November 2019:
Further research continues around optimal male hatchling numbers and where these interventions are needed most.

Thank you

This project would not be possible without the help of our volunteers. A special thank you to: 


  • Melissa Staines
  • Dr. Ian Bell
  • Jeremy Raven
  • Sara Kophamel
  • Bella Reboul
  • Alastair Freeman
  • Sophie Thomas
  • Brittney Zendler
  • Danny Panizo Coronado
  • Lauren O'Brien
  • Johanna Karam
  • Kerri Woodcock
  • Stephen Menzies
  • Edith Shum
  • The Western Cape Turtle Threat Abatement Alliance
  • James Cook University