Boom time for Cape Verde’s sea turtles as conservation pays off
The number of nesting sites on the archipelago has risen dramatically, but global heating sees male population plummet
Last modified on Tue 26 Oct 2021 07.00 EDT
It’s nearly midnight as Delvis Semedo strolls along an empty beach on the Cape Verdean island of Maio. Overhead, the dense Milky Way pierces the darkness. A sea turtle emerges from the crashing waves and lumbers up the shore. Then another. And another.
Semedo is one of about 100 local people who patrol Maio’s beaches each night during nesting season to collect data on the turtles and protect them from poachers. This year has been busier than usual. Sea turtle nests on the islands of Sal, Maio and Boa Vista – the primary nesting grounds for loggerheads in Cape Verde – have soared in the last five years. Cape Verde’s environment ministry puts nest numbers in 2020 across all 10 islands at almost 200,000, up from 10,725 in 2015.
The West African island nation was considered the world’s third-largest nesting site for loggerheads (in terms of numbers of nesting females), after Florida and Oman. But nest numbers have risen so dramatically in recent years that some scientists believe Cape Verde to be the second largest, or even largest.
While Covid-19 travel restrictions have provided a break from human disturbances, experts believe conservation measures are the biggest factor behind the increase in nesting numbers.
“Conservation efforts in Cape Verde began 20 years ago – that’s the time it takes for baby turtles to come back as adults,” says Albert Taxonera, founder and co-director of Project Biodiversity, a Cape Verdean conservation organisation.
Cape Verdean NGOs monitor hundreds of kilometres of sandy coastline each year during nesting season. Patrollers like Semedo are tasked with protecting as many turtles as possible on their designated stretch of beach. Each turtle must be measured, fitted with a tracking chip and monitored to ensure it returns safely to sea.
For centuries, the slow-moving reptiles were considered a free, easily obtainable food source. But economic growth has made other sources of protein more accessible and education initiatives have raised awareness of the plight of the sea turtle.
“Before, I just thought of them as food,” Semedo says. “But since the first day I saw a turtle, I knew I wanted to protect them.”
In 2018, Cape Verde also toughened existing laws and criminalised the killing, trade and consumption of sea turtles. Offenders are typically fined or given community service, which can involve beach patrol with the NGO that caught them.
It is not just Cape Verde’s sea turtles that are thriving. Beaches from India to the US have also seen exponential increases in nesting, and the same factors could be at play.
“If you look at the number of sea turtle projects that are out there now, compared to what you had 30 years ago, there are hundreds of them,” says Rod Mast, co-chair of the IUCN’s marine turtle specialist group and chief editor of the State of the World’s Sea Turtles report. “We’re doing a really good job of protecting them.”
Besides conservation efforts, some scientists think nesting numbers could be linked to ocean productivity. If there is a high density of nutrients in the ocean in a given year, for example, turtles will have enough energy to nest.
A global decline in sharks, which prey on sea turtles, is another possible factor. Shark and ray populations have dropped by more than 70% since 1970 due to overfishing.
Despite recent progress, myriad threats remain for sea turtles and some populations are facing steep declines. Many leatherback subpopulations are classified as critically endangered by the IUCN, for example, and hawksbill turtles are also nearing extinction.
Scientists say the main culprit is fishing nets, which can trap and drown sea turtles. Plastic pollution is also responsible. Floating bags can be easily mistaken for jellyfish, which turtles feed on, and microplastics are ubiquitous throughout the oceans.
Protecting beaches is not enough – we must focus also on protecting turtles at sea, Mast says. “The ocean is unhealthy in systemic ways, and there’s only two things wrong with it: what people put in it and what people take out of it,” he says. “And so the common denominator there is people.”
People must change their behaviour around seafood consumption, carbon output and plastic use in order to save the turtles, he adds.
In the long term, global heating may be the biggest threat. A turtle’s sex is determined by the temperature of the sand the egg is buried in, and as this rises, gender ratios are being skewed. On Maio, for example, nearly 100% of hatchlings in 2019 and 2020 were estimated to be female.
A diminished male population not only affects reproduction, but decreases genetic diversity, which can hinder the ability of species to adapt to environmental changes. Conservation efforts, which focus on protecting nesting females, may be compounding this issue, says Juan Patino-Martinez, scientific coordinator at the Maio Biodiversity Foundation.
“Genetically, they are headed towards extinction,” he says. “We need more males.”
Coastal development, particularly of tourist resorts next to nesting beaches, is another major concern. Sal is already home to dozens of beach resorts and hotels, and this year Cape Verde approved the construction of a massive luxury tourism and business complex on the pristine shores of Maio.
“We are destroying their habitats and causing global warming, but we are also implementing very strong conservation programmes,” Patino-Martinez says. “So it depends on the humans. We can cause their extinction or we can conserve them.”