Mediterranean green turtles set to expand their nesting area under climate change

The more the climate warms, the further green sea turtles will expand their nesting range along the Mediterranean Coast, according to international researchers who say their nesting range could expand by over 60% under worst-case climate scenarios. The sex of green sea turtle offspring is impacted by their incubation temperature, meaning climate change has significant impacts on their breeding. The researchers developed a model to predict the suitability of areas along the Mediterranean coastline and looked at how climate change scenarios impacted the range of suitable areas. They say warming is likely to expand the suitable nesting range across much of Italy, Greece, the south Adriatic Sea and the North African coastline, however many of these increases would bring them into closer contact with humans, putting their nests at additional risks.

Journal/conference: Scientific Reports

Link to research (DOI): 10.1038/s41598-023-46958-4

Organisation/s: Viale Dell’Università, Italy

Funder: The authors acknowledge the work and effort of all studies used in this study. We would like to thank all researchers,
organizations and associations that monitor beaches collecting and publishing nesting data along the coasts
of the Mediterranean Sea

Media release

From: Springer Nature

Ecology: Mediterranean green turtles nesting range expands under warming climate *VIDEO & IMAGES*  

Rising global temperatures could lead to an increase in the nesting range of green turtles in the Mediterranean Sea, according to a modelling study published in Scientific Reports. Under the worst-case climate scenario, the nesting range could increase by over 60 percentage points, spreading west from the current area to include much of the North African, Italian, and Greek coastlines.

Human-caused climate change has caused sea surface temperatures to increase globally, with severe impacts on some marine life. Sea turtles are potentially particularly susceptible, as the sex of their offspring is dependent on incubation temperature. Although previous research has investigated the effects of climate change on several different populations of sea turtles worldwide, there has been very little research into the green turtle (Chelonia mydas) population in the Mediterranean Sea.

Chiara Mancino and colleagues developed a model for predicting the suitability of a point on the Mediterranean coastline as a green turtle nesting location. The authors first assessed the predictive power of the model by evaluating it against 178 confirmed nesting locations, recorded between 1982 and 2019 and mainly limited to Turkey and Cyprus in the eastern Mediterranean. They found that the model had a very good predictive power, and that sea surface temperature, sea salinity, and human population density most affected the suitability of a specific location as a nesting site.

The authors then modelled how four different greenhouse gas emission scenarios could affect the nesting range of green turtles in 2100. They found that progressively worse climate scenarios were associated with greater increases in the nesting range in the Mediterranean. Under the worst-case climate scenario modelled, the nesting range increased by 62.4 percentage points, and included the North African coastline to Algeria, much of Italy and Greece, and the south Adriatic Sea. However, the authors warn that this increase in green turtle nesting range in the heavily populated central and western Mediterranean would bring them into increased contact with humans and urbanised beaches, which could negatively affect nesting success. Future research should investigate how such effects can be mitigated.

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