Sea turtles in the Caribbean Netherlands: visible recovery, threats remain
Naturalis Biodiversity Center, Wageningen University & ResearchSea turtles have a remarkable life cycle. After hatching, the young turtles enter the open sea, where they remain out of sight for years. Only around their 25th to 35th year, as with the green sea turtle, do they return to their birthplace to nest. This long lifespan and strong site fidelity of sea turtles makes them especially vulnerable to disruption both at sea and on land.
Threats
In Dutch, the green sea turtle is also known as soepschildpad, which translates to 'soup turtle'. A name that refers to a time when sea turtles were a major food source in the Caribbean. In this day and age, sea turtles are protected, and it is forbidden to eat them. However, that does not mean these animals are free from human threats.
On beaches, coastal development, artificial light, erosion, and recreation cause problems for nesting. At sea, turtles face pollution, loss of seagrass beds, declining coral reefs, and the consequences of increasing recreational activities, such as boat collisions. As turtles forage in the same areas for years, they are vulnerable to environmental pollution. On Bonaire, in particular, heavy metals like cadmium and copper exceed safety thresholds in seagrass. Chemical pollution can cause turtles to be more susceptible to diseases like fibropapillomatosis, a herpes virus that causes tumors.
Important foraging areas
The waters around the Caribbean Netherlands have become increasingly important as foraging areas for turtles. On Saba, juvenile green turtles graze in seagrass beds, while hawksbill turtles are regularly seen on the reefs and the nutrient-rich Saba Bank. On Bonaire, green and hawksbill turtles are widespread, with high numbers of green turtles around Lac Bay, an important area for seagrass.
Lisa Becking, researcher at Naturalis and associate professor at Wageningen University & Research, sees reason to be cautiously optimistic about the future of sea turtles in the Caribbean Netherlands. “Twenty years of monitoring show that sea turtle numbers remain relatively stable. Genetic research indicates that juvenile green turtles, in particular, originate from recovering populations in the northwestern Caribbean. The influx of turtles from other regions is decreasing however. This suggests that population recovery is less strong in other parts of the Caribbean.”
International cooperation
The threats to turtles are not limited to the islands themselves. During their long migrations between breeding and foraging grounds they face dangers as well. “Nicaragua, for example, is responsible for a large portion of green sea turtle catches in the Caribbean, by some estimates. And those just happen to be the waters where many nesting sea turtles from Bonaire like to spend their time,” Becking explains.
Sea turtles often travel thousands of kilometers between their nesting beaches and foraging grounds. Conservation on a single island is therefore not enough. According to Kaj Schut, manager of Sea Turtle Conservation Bonaire, international cooperation –even with countries where fisheries and habitat disruption are still major risks – is essential. “Thanks to satellite research, we know that sea turtles travel enormous distances. A turtle nesting in Bonaire can migrate to Nicaragua to forage. This means that protection does not stop at the island borders.”
Differences between species and islands
There has been a huge increase in the number of observed nests of green sea turtles, hawksbill turtles and loggerhead turtles on Bonaire since 2003. This is in part thanks to the increased monitoring of nesting areas by Sea Turtle Conservation Bonaire. But an increase in the number of green sea turtle nests has also been observed on Sint Eustatius. For hawksbill and loggerhead turtles, the number of nests there remains the same. For the leatherback turtle, however, the situation is very worrying. The number of nests on Sint Eustatius has dropped significantly in recent years, to almost zero. Saba has no suitable beaches for sea turtles to nest on, and therefore, no nests have been observed in recent years.
The report also shows that the quality of monitoring differs per island. According to Eleanor Butler, marine park manager at St. Eustatius National Parks, this is primarily due to the available resources. “Bonaire has a robust, long-term dataset, which allows for reliable trend analysis. Due to a lack of capacity, sometimes data is lacking from Sint Eustatius and Saba, which makes it difficult to properly track local developments or make timely adjustments. This emphasizes the need for continuous monitoring and targeted protection, especially in places with a lot of human activity. Bonaire's long-term data provides a valuable basis for effective management.”
A perspective on recovery
Sea turtles are indispensable for healthy ecosystems. The recovery of some populations proves that conservation measures are effective – as long as they are sustained and scientifically supported. According to Becking, the Caribbean Netherlands offers a unique prospect on recovery. “By building on the successes on Bonaire, improving monitoring, and addressing threats in a targeted way, these extraordinary animals can continue to thrive in our coastal waters. But this requires sustained commitment – from policymakers, researchers, and the local community. This is the only way to ensure a future where turtles continue to return to our beaches.”
Recommendations from the report
To better protect sea turtles, the researchers make four concrete recommendations in their report:
Protect the habitat: Restore and protect beaches and seagrass beds from construction, light pollution, and disruption, and control water quality.
Collect better data: Structural monitoring on all islands is needed, including research into chemical pollution in turtle tissues.
Increase awareness: Tourists and residents have a role to play in protecting turtles, for example, by keeping a distance and not disturbing nests.
Collaborate: A new, joint Sea Turtle Recovery Action Plan (STRAP) must strengthen cooperation within the Kingdom and with neighboring countries.
More information
Text: Naturalis Biodiversity Center & Wageningen University & Research
Images: Fee Smulders (lead photo: green sea turtle near Bonaire); Maggy Nugues