FEMALE OF THE SPECIES
Warming climate turning baby sea turtles all one gender, study shows
BOA VISTA, CAPE VERDE She emerged from the ocean just before midnight, clambering up the shore as her ancestors have for 200 million years.
Only stars glowed on this remote beach where the sea turtle arrived to lay her eggs. She dodged plastic, fishing nets and oil spills to get this far. But another threat to her species lurks in the ground: sand temperatures that foster only one gender.
“One hundred per cent girls,” whispered the biologist, crawling next to the pregnant reptile. “This nest will be 100 per cent girls.”
As the Earth gets hotter, turtle hatchlings worldwide are expected to skew dangerously female, scientists predict, making the animals an unwitting gauge for the warming climate.
On the tiny West African island nation of Cape Verde — home to a sixth of the planet’s nesting loggerhead turtles — the disparity is stark. Eighty-four per cent of youngsters are now female, researchers from Britain’s University of Exeter found in a July report.
Populations in Florida and Australia are also showing dramatic sex imbalances, sparking fears that creatures that outlasted dinosaurs are plodding toward extinction.
“Males here could vanish in two or three decades,” said Adolfo Marco Llorente, a Spanish researcher who camps every summer on Boa Vista, one of Cape Verde’s 10 islands in the Atlantic. “There will be no reproduction.”
The past five years have been the hottest on record for the globe. Roughly a tenth of the planet has warmed beyond two degrees Celsius, according to a Washington Post analysis — the point at which scientists say rising temperatures can trigger irreversible damage to ecosystems. Here in Cape Verde, the warming is above average — about 1.3 C just since 1964, based on records from the primary airport.
If the trend continues at the Intergovernmental Panel on Climate Change’s lowest projection, researchers estimate that fewer than one per cent of the country’s sea turtles will be born male by the century’s end. Higher rises could wipe them out completely.
This has raised alarm on the archipelago, which ties its economy to the roughly 30,000 sea turtles that annually swim here to nest. (Tourism accounts for 15 per cent of economic growth.)
Turtle murals greet thousands of visitors each week. Turtle pottery rakes in cash. Turtle-shaped roundabouts ease traffic. Turtle signs urge four-wheelers to stay off the sand.
“Turtles are the brand of Cape Verde,” said Paulo Veiga, the country’s assistant secretary of state for the maritime economy.
The Cape Verdean government works with non-profit organizations to protect the reptiles, tapping money from hotel taxes for beach cleanups, security to curb poachers and fences that keep away such predators as ghost crabs.
Turtle guides on the islands, who lead visitors largely from Europe on overnight beach treks, are mandated to educate them about climate change.
“They see the turtles like toys,” said Manuel Delgado Rodrigues, who has arranged such tours for two decades. “We have to tell them about the problems.”
The U.S. Fish and Wildlife Fund also supports conservation projects on the islands. It spent US$53,800 on the effort in 2018.
Not everyone thinks such tactics stand a chance.
“Humans can do nothing about that,” said Djamilton Ramos, a Boa Vista city council member.
Humans don’t know why the environment shapes the gender of some lizards, crocodiles and various species of sea turtles. Even slight shifts in the land can warp their reproductive fate.
Sea turtle eggs that incubate in sand below 27.7 C produce males, according to the National Oceanic and Atmospheric Administration, while nests about 28 C to 30 C create a gender mix. Anything higher than 31 C, though, is 100 per cent female.
Tourists won’t see the effects immediately, said Lucy Hawkes, the English ecologist who led a study on Boa Vista., because the animals can live for 100 years and lay more than 1,000 eggs. Plus, sea turtles are polyamorous. One male can find dozens of sexual partners.
Scientists have been testing methods to cool the nests. Gently digging up eggs and moving them to shadier parts of the beach has worked. So do sprinkler systems and dividing offspring into smaller batches, since eggs crammed together tend to warm each other up. The Washington Post