05-02-2023

Sea level rise threatens turtle breeding grounds

An international team of scientists has recently found that sea level rise could lead to the flooding of sea turtle breeding grounds in Australia, the Dominican Republic, Costa Rica, and the United States, contributing to a significant loss of turtle nesting sites, with leatherback turtle nests being the most vulnerable.

The experts estimated the likelihood of flooding in 2,835 sea turtle nest locations across seven breeding grounds from 2010 to 2100, under moderate and high greenhouse gas emission scenarios (the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways known as RCP 4.5 and 8.5). 

These breeding grounds are situated in various locations, including the Mondonguillo beach in Costa Rica, the Guanahacabibes peninsula in Cuba, the Saona Island in the Dominican Republic, the coast of Ecuador, the Raine Island in Australia, the St. George Island in Florida, and the Sint Eustatius in the Caribbean Netherlands. The breeding sites serve as habitats for five different sea turtle species – the leatherback, loggerhead, hawksbill, olive ridley, and green turtles.

The analysis revealed that breeding grounds situated on flat beaches are at the highest risk of flooding under a moderate emissions scenario (RCP 4.5). For instance, 100 percent of nests located on Raine Island and Saona Island – which are at low elevations on flat beaches – are projected to be vulnerable to flooding by 2050. 

In addition, the scientists estimated that 100 percent of nest locations at St. George Island and Mondonguillo beach may also face the risk of flooding under the same emissions scenario.

In breeding grounds used by multiple species, leatherback turtle nests may be especially vulnerable to flooding due to variations in the nesting locations preferred by each species.

Leatherback turtles tend to nest in open areas near the high tide line, and hawksbill and green turtles prefer higher elevations closer to steep cliffs or dunes. Thus, in Sint Eustatius, 50 percent of leatherback, 18 percent of hawksbill, and 13 percent of green turtle nests may be vulnerable to flooding by 2050 under a moderate emissions scenario.

Since female sea turtles usually return to nest on the same beaches they hatched on, sea level rise could lead many turtles to nest on flooded beaches and thus negatively impact the number of turtles hatching. 

Further research is needed to investigate how quickly turtles could adapt to such phenomena in order to clarify the long-term impact of sea level rise on turtle populations. In the meanwhile, strategies to mitigate the impact of sea level rise and increase turtle resilience – including sand refilling on nesting beaches, nest relocation, and the use of turtle hatcheries – are urgently needed. 

“If the world maintains current carbon dioxide emission rates, worst-case scenarios might be vastly underestimated by 3-4 times and existing management strategies may then be insufficient to protect the future of many sea turtle populations worldwide,” wrote the researchers.

“In summary, our study predicts massive flooding at important rookeries in Australia, Dominican Republic, Costa Rica, and the USA. These critical areas will face the effects of sea level rise in the next few decades, meaning that it is now urgent to reduce anthropogenic emissions to safeguard the future of sea turtle populations against climate change and associated sea level rise.”

The study is published in the journal Nature Scientific Reports.

By Andrei Ionescu, Earth.com Staff Writer

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