Sea turtles are likely to be beneficiaries of a warming climate as hotter incubation conditions trigger a rising share of female hatchlings that could lift natural rates of population growth, new research shows.
But gains will be temporary if temperatures keep rising and nudge populations towards becoming all female or exceed levels at which developing embryos die, the study, to be published in Nature Climate Change on Monday, found.
"There'll be a bit of a breathing space … but down the track it'll be serious," said Graeme Hays from Deakin University, one of the report's authors.
It's been known for decades reptile reproduction is highly sensitive to temperature, with the ratio of male to female offspring varying. For species of sea turtles, the pivotal temperature is an oddly uniform 29 degrees for incubation, beyond which more females emerge from the eggs.
At about 30.5 degrees, populations become fully female.
As remaining males die off, "it will be end of story without human intervention", Professor Hays said. At higher than 33 degrees, embryos don't survive.
The study focused on a globally important loggerhead turtle rookery on the Cape Verde Islands in the Atlantic but its results also apply to species elsewhere, including the Pacific.
It found that light-coloured sandy beaches already produce 70.1 per cent females, while beaches with darker sands are at 93.5 per cent.
The findings should help steer conservation efforts to make a priority of protecting lighter-coloured sandy beaches or planting more vegetation near dark ones to ameliorate the warming, Professor Hays said.
"If you have to build a hotel, build it behind the dark-coloured beach," he said.
Since breeding populations are likely to swell in coming decades, sea turtle adult populations are "unlikely to be dire in the next 150 years", the paper said.
Professor Hays said any near-term increase in turtles would be modest compared with past populations.