Warming oceans threaten sea turtle reproduction

A Golfina sea turtle (Lepidochelys olivacea) leaves at dawn after having spawn at Morro Ayuta Beach, state of Oaxaca, Mexico on 10 September, 2015AFP file photo

Rising sea temperatures are threatening sea turtle populations by warming their nesting sites on beaches across the world, a new study found Wednesday.

The climate change-fuelled phenomenon could cause local extinctions of the already threatened reptiles, which have a long breeding cycles and are slower to adapt than many other species, such as birds or butterflies.

Sea turtles dig holes and lay their eggs in the sand, which has become warmer in recent years thanks to rising sea temperatures caused by global warming.

Warmer nest temperatures produce more female offspring, thus risking overwhelmingly female populations that will have trouble finding mating partners in the future.

Many nesting sites today are heavily female-biased today, suggesting rising temperatures are already having an impact.

High temperatures at nesting sites can also decrease hatchling production.

Wednesday's study looked at whether sea turtles could shift their breeding period to cooler parts of the year in order to bring nest temperatures down.

In the first global study of its kind, researchers modelled how sea turtles could mitigate the impact of a global temperatures rise of 1.5 degree Celsius -- the best case scenario outlined by the United Nations -- at 58 nesting sites around the world.

On current trends, the world is headed for in increase of 2.6C above the preindustrial benchmark.

They found that moving the breeding period mitigated about 55 percent of sea water warming, meaning that in about 45 percent of cases the nesting was at risk.

'Band-aid' fixes

"These findings underscore concerns for the long-term survival of this iconic group," said the report published in the Royal Society Open Science Journal.

Lead author Jacques-Olivier Laloe told AFP the findings point to the "really worrying" possibility that local extinctions could ensue.

The work found that sea turtles breeding at higher latitudes did benefit when they moved their nesting period to a period with cooler weather.

But this was harder for sea turtles living near the equator where temperatures are less likely to fluctuate seasonally, the report said.

Scientists warn that global temperatures are likely to warm beyond 1.5C, possibly by mid-century, which means the study's findings are likely "optimistic results", said Laloe of Australia's Deakin University.

"In reality, it's likely that sea turtles have less adaptive potential to climate change," he said.

There are a few ways that humans can help to cool the nests, such as providing shade or watering the sand. But these are "temporary 'band-aid'" fixes, according to the authors.

"Solutions to address climate change, like reducing greenhouse gas emissions, switching to renewable energies, and changing land-use patterns are required to reduce future climate change impacts," the study said.

The researchers said the modelling could apply to other reptiles whose breeding success is temperature-dependent and thus vulnerable to climate change, such as crocodiles and tortoises.

The research looked at all seven sea turtle species, six of which are already on the International Union for Conservation of Nature's Red List of Threatened Species.