Delta blues: why estuaries are the canaries in the climate crisis coalmine
These fragile ecosystems are where the impacts of the climate crisis are often felt first, say experts
The Ebro delta appears to be in robust health, to a casual observer. There is water gurgling in the canals and irrigation channels, and what appears to be a mighty river flowing into the sea. The dazzling green rice fields are dotted with ibis, egrets and redshanks.
However, all is not what it seems. The Ebro, the only one of Spain’s three great rivers that flows into the Mediterranean, is one of the most abused and exploited in Europe.
It rises in Cantabria in northern Spain and along its 910km (560-mile) course its waters are interrupted and extracted by 70 dams before it drains, literally exhausted, into the Mediterranean in southern Catalonia.
More than 90% of the sediment, the lifeblood of the delta that feeds the shellfish offshore and fertilises the paddy fields, is dammed upstream and never reaches the sea.
“In a healthy delta there would enough sediment to cope with rising sea levels, even with climate change,” says Maite Martínez-Eixarch, a biologist at the Institute of Agrifood Research and Technology (IRTA), based in Sant Carles de la Ràpita in the delta. “It’s part of a natural system. But 99% of the sediment is captured by the dams.”
The Ebro is the climate crisis equivalent of the canary in the coalmine. Estuaries and river deltas act as an early warning that all is not well, from rising sea levels to invasive species.
Spain’s east coast is soft, made up of dunes and mudflats, and in areas such as the Ebro delta, not only is the sea rising but the land is sinking. About 70% of the delta is only 50cm (20in) above sea level and, with rising sea levels and without the sediment to hold it back, the sea is gaining ground, eroding the coast at a rate of five metres a year.
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