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Nesting range of green turtles will explode in a warmer climate 

A new study predicts a significant expansion in the nesting range of green turtles (Chelonia mydas) due to rising global temperatures.

The Mediterranean green turtle is a species that is often overshadowed in climate change discussions.

A team of researchers led by Chiara Mancino has unveiled how global warming could reshape the nesting dynamics of these turtles, potentially altering the ecological landscape of the Mediterranean.

Study background 

“Climate change is reshaping global ecosystems at an unprecedented rate, with major impacts on biodiversity. Therefore, understanding how organisms can withstand change is key to identify priority conservation objectives,” wrote the study authors.  

“Marine ectotherms are being extremely impacted because their biology and phenology are directly related to temperature. Among these species, sea turtles are particularly problematic because they roam over both marine and terrestrial habitats throughout their life cycles.”

Transforming the coastline 

The experts theorized that nesting ground availability for green turtles will increase in the Mediterranean following hotter summers and winters, shifting their nesting locations in response to rising temperatures.

Based on their modeling study, the team predicts that the turtles will expand their nesting range by 60 percent under the worst case emissions scenario. 

This expansion is set to transform the Mediterranean coastline, extending the turtles’ nesting grounds beyond their current range in Turkey and Cyprus to vast stretches of North African, Italian, and Greek shores.

High predictive accuracy 

For the investigation, Mancino and colleagues developed a model to predict the suitability of various points on the Mediterranean coastline as green turtle nesting locations.

First, the researchers tested the predictive accuracy of their model against 178 verified nesting sites recorded from 1982 to 2019. The findings revealed a high predictive accuracy, with sea surface temperature, salinity, and human population density emerging as pivotal factors influencing nesting site suitability.

Key insights on green turtles

The researchers analyzed four distinct greenhouse gas emission scenarios and their implications for green turtle nesting by 2100. 

The correlation was clear: more severe climate conditions led to a broader nesting range. The worst-case scenario predicted a dramatic 62.4% increase in nesting range, extending to the North African coastline up to Algeria, significant parts of Italy and Greece, and the southern Adriatic Sea.

“Our models show an increase in nesting probability in the western Mediterranean Sea, irrespective of the climate scenario we consider. Contrary to what is found in most global change studies, the worse the climate change scenario, the more suitable areas for green turtles will potentially increase,” wrote the study authors. 

Further research is needed

However, this potential expansion is not without its challenges. The experts 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 urbanized beaches, which could negatively affect nesting success. 

The researchers emphasize the urgency for future studies to focus on mitigating these potential negative impacts. 

“To better inform future management of marine turtles, there is the need to understand future threats, as well as to couple predictions of marine turtle distribution with an assessment of exposure to these threats,” wrote the study authors.

Green turtles and biodiversity collapse

The Mediterranean Sea represents one of the most vulnerable regions in the world when considering the impacts of global warming, noted the researchers.

“The Mediterranean has always been hugely exploited by humans, with important and potentially negative interactions between human activities and climate changes.”

“The basin currently hosts more than 500 million inhabitants, a third of whom live along the coasts, and is the first tourist destination in the world with 360 million visitors per year.” 

“The combination of climate change and human impacts clearly generate the starting baseline for a biodiversity collapse, especially for species exploiting at the same time marine and terrestrial habitats as sea turtles.”

The study is published in the journal Scientific Reports.


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