For approximately 3 000 years, generations of green sea turtles have returned to the same seagrass meadows to eat. This was discovered by Willemien de Kock, a historical ecologist at the University of Groningen, by combining modern data with archaeological findings. Sea turtles migrate between specific breeding places and eating places throughout their lives-this much was known. But the fact that this stretches over many generations highlights the importance of protecting seagrass meadows along the coasts of North Africa. The results were published in PNAS on July 17.

 

Along the coasts of the eastern Mediterranean Sea, volunteers are active to protect the nests of the endangered green sea turtles. However, as Willemien de Kock explains: 'We currently spend a lot of effort protecting the babies but not the place where they spend most of their time: the seagrass meadows.' And crucially, these seagrass meadows are suffering from the effects of the climate crisis.

 

Why is it relevant to know the eating habits of a species over many past generations? Because we collectively suffer from the shifting baseline syndrome: slow changes in a larger system, such as an animal population, go unnoticed because each generation of researchers redefines what the natural state was, as they saw it at the start of their careers. 'Even long-term data goes back only about 100 years,' says De Kock. 'But tracing back further in time using archaeological data allows us to better see human-induced effects on the environment. And it allows us to predict, a bit.' In fact, recent models have shown a high risk of widespread loss of seagrass in precisely these spots where green sea turtles have been going for millennia. Which could be detrimental to the green sea turtle, precisely because of its high fidelity to these places.