Of all the potential consequences of climate change—rising sea levels, desertification, floods—here’s one that may not be on your radar: climate change is producing an abundance of female turtles.
For green turtles, the future is female. Unfortunately, the future is also in doubt.
More than 52 percent of all green turtles are born female, and new research suggests the number will grow as the climate warms. By the end of the century, scientists estimate, as many as 93% of green turtle hatchlings could be female.
The sex of sea turtle hatchlings is not dependent on the passing down of chromosomes, like in humans. Rather, sea turtle sex is a function of incubation temperature.
The estimate is based on field observations and experiments conducted in Guinea-Bissau, West Africa, but researchers think temperature increases will have similar impacts on green turtles elsewhere.
Initially, the increasing number of females would translate to more nests and more offspring, but scientists think rising temperatures could eventually push incubation temperatures above lethal levels.
"Although rising temperatures will lead to more female hatchlings -- and 32 to 64 percent more nesting females by 2120 -- mortality in eggs will also be higher in these warmer conditions," Rita Patricio, an ecologist at the University of Exeter, said in a news release. "As temperatures continue to rise, it may become impossible for unhatched turtles to survive."
Additionally, rising sea levels could wipe out more than a third of the green turtle's nesting sites. At the beach in Guinea-Bissau, there is room for turtles to move and find new nesting sites.
"In other places there may be natural barriers or human constructions that stop beaches moving inland," Patricio said.
Patricio and her colleagues published their findings this week in the journal Global Change Biology.
“Combining our results with temperature data show that the northern GBR green turtle rookeries have been producing primarily females for more than two decades and that the complete feminization of this population is possible in the near future,” the authors write in the paper.
Despite the dramatic changes predicted in the study, the authors think green turtles in Guinea-Bissau will be able to adapt -- at least until the end of the century.
"Our results suggest the nesting population of green turtles the Bijagós Archipelago, Guinea-Bissau, will cope with the effects of climate change until 2100," Pactricio said. "Cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee some hatchlings are male."
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