Sea levels rising: The new threat that could displace sea turtles from Israel's beaches

As the sea turtle hatching season along Israel's coast nears its end, the question arises: Will female sea turtles be able to continue laying their eggs here in 70 years? Israel's Mediterranean coast serves as a habitat for hundreds of loggerhead and green sea turtle nests each year. Both species are protected and exposed to a variety of threats at sea, such as predation, direct strikes by vessels, ingestion of plastic bags, and entanglement in fishing nets, as well as land-based threats to nests on the beach. According to a new study, the expected rise in sea levels due to climate change could harm the ability of female sea turtles to come ashore to lay eggs.

During the breeding season from May to August, female sea turtles come ashore to lay their eggs, depositing several dozen eggs per clutch. The hatching season occurs from August to October, when the hatchlings emerge from the eggs buried in the sand and make their way to the sea, totaling several thousand each year in Israel. Usually, adult female turtles return to lay eggs on the same beach where they hatched. However, in cases of disruption, such as light pollution or changes to the shoreline, they may refrain from laying their eggs on the beach altogether.

"According to data we have collected over recent decades, the vast majority of nests are placed in sandy areas within 50 meters of the water," said Shelly Elbaz, head of remote sensing at the Nature and Parks Authority, who worked on the study with Dr. Asaf Tsoar, Yael Avidan, Dr. Ofer Steinitz, Dr. Yaniv Levy, and Dr. Noam Leader. "Under any future scenario, a continuous strip of exposed sand that is at least 50 meters wide will allow nesting to continue without disruption." Suitable nesting habitats are beaches free of established vegetation and obstacles such as cliffs or roads.

The study, presented at the 54th Annual Conference for Science and the Environment, examined sea level lines along Israel's coastline over the coming decades, based on several scenarios presented in a report by Israel Oceanographic and Limnological Research. The results indicate that the potential area available for sea turtle nesting along Israel's Mediterranean coast could shrink significantly.

Study data show that by 2100, there could be a 23% reduction in the total beach area within the 50-meter range, the area suitable for nests. A focused examination of different beaches reveals several locations at heightened risk of losing area. For example, the beaches of South Acre, Rosh Carmel, and Sironit-Blue Bay could lose more than 85% of their average width. Under the worst-case scenario, 96% of the beach width between the north of the Tel Aviv Marina and the south of the Tel Aviv Port is set to disappear. For instance, if there are currently 50 meters of beach available for nesting, only two meters will remain by 2100. "In the case of a narrow beach strip, the female sea turtle might make do with the smaller area, but the change and strain could also affect her. In any case, this presents a new challenge for the turtle population, and as with other disruptions, she may return to the water without laying her eggs at all." In such cases, the turtle may attempt to lay eggs again the following night, but if she fails again, she may drop the eggs in the sea, where they will not survive. It is also possible that the eggs will not be laid and will rot inside her body instead, which could lead to her death.

Alongside the reduction in beach area, researchers examined the percentage of nests that could end up in high-risk zones, such as beyond a road or a cliff, due to changes in the beach terrain. Under the worst-case scenario, about 40% of all nests in 2100 will be located in high-risk areas. More vulnerable regions were identified here as well. For the loggerhead sea turtle, the Sharon region in general and the Ma'agan Michmoret beach in particular were marked as the most vulnerable. For the green sea turtle, the southern coastal plain in general and the beach south of the Ashkelon Marina in particular were identified as the most vulnerable.

Sea levels have risen at an accelerated rate over recent centuries, primarily due to the burning of fossil fuels and greenhouse gas emissions that cause ocean warming and accelerate polar ice melt. According to a report by the Intergovernmental Panel on Climate Change (IPCC), the global rate of sea level rise during the 20th century averaged about 1.4 mm per year, faster than in any other century over the last 3,000 years. Elbaz emphasized that while the study focused on coastline changes due to climate change, it did not account for additional coastal processes such as sand erosion, land-use changes, or extreme weather events that could also impact habitat availability and turtle nesting behavior.

In addition to nationwide mapping, localized measurements were conducted to compare adjacent areas along the same beach. "We sampled according to spatial units of tens of meters each," Elbaz said. "This allowed us to see a mosaic of vulnerability and stability clusters, and what surprised me was the degree of variance between neighboring areas. The beach is not homogeneous. Within the same beach, you can see a sequence of stable units immediately followed by a sequence of sensitive units. This variance could potentially benefit the turtles, as they might adapt more easily to the changes and find an area close to where they hatched and to which they return."

The study's findings could be relevant in the short term. First, Elbaz noted the need to identify and monitor these highly sensitive beaches and areas and to factor this vulnerability into planning processes. "Our next step is to hold meetings in various regions with field and planning personnel, present the findings, and collaborate on how this new information can improve the protection of ongoing sea turtle activity. Additionally, we can preserve stable areas alongside sensitive ones so they can serve as nesting reserves and bolster adjacent areas that may be impacted," he concluded.