New research shows that the number of green turtles breeding in Cyprus has skyrocketed in recent years — but that rebound depends heavily on an Egyptian lake where many turtles feed.
Green turtles, an endangered species, spend most of their lives foraging in one area, but return to shore where they hatch to lay their eggs.
The new study, conducted by the University of Exeter and the Northern Cyprus Society for Turtle Conservation (SPOT), tagged and followed females laying eggs at the main foragers (breeding beaches) in Cyprus, and 74% foraged in Lake Bardawil in Egypt.
The study found that nest numbers have nearly tripled since the early 1990s — but reliance on some feeding sites, particularly Lake Bardawil, leaves turtle populations vulnerable if conditions change there.
“Since about 2010, our tracking of turtles from Cyprus has shown a significant increase in the number of foragers in Lake Bardawil,” said Dr Robin Snape, from the Center for Ecology and Conservation at the Exeter Penrhyn campus in Cornwall.
“At the same time, the number of adult feeding turtles has decreased around Cyprus and Turkey – possibly due to higher by-catch (bycatch) of turtles in fisheries there.
“The overall increase in nest numbers appears to be driven by protection of nesting sites in Cyprus and conditions at Lake Bardawil.
“It is likely that the lake will reach its carrying capacity, at which point the number of green turtles can stop increasing.”
Bardawil Lake is a man-made hole lake that connects to the sea, allowing marine life including turtles to swim in and out.
It was created in the 1950s as a fishery, but has become an ideal seaweed habitat for adult green turtles, which are more than a meter long and weigh more than 100 kg.
The new study used long-term satellite markers to track 19 female nesting turtles in key foragers on the Karpaz Peninsula, Cyprus.
While most of the turtles went to Lake Bardawil, one migrated 1,500 miles (2,400 kilometers) to the island of Djerba, Tunisia – the longest distance recorded so far for a Mediterranean green turtle.
By comparing the oldest three-year average nest counts (1993-1995) with nest counts conducted as part of this study (2017-2019), the average annual nest count increased from 186 to 554.
“Given the importance of Lake Bardawil to green turtles in the eastern Mediterranean, it is essential that the habitat there is managed in a way that protects the turtles and supports the livelihoods of fishermen,” said Professor Annette Broderick of the University of Exeter.
“Reducing bycatch and protecting habitats in other locations can also increase green turtle numbers and reduce dependence on that single location.”
The study was funded by the MAFA Foundation and the Natural Environment Research Council.
The paper published in the journal Global environment and conservationentitled: “Recovery of green turtle populations in the Mediterranean increasingly depends on Lake Bardawil in Egypt.”