“It’s a slow-motion tsunami, but it’s a tsunami, a wave that keeps getting bigger. ” Co-coordinator of the report “A coastline reaching its limits” published in early September, commissioned by the Spanish region of Catalonia to take stock of the state of the coast under the influence of climate change, Carles Ibanez is categorical. “For the time being, citizens are well aware of the rise in temperatures and flooding, but when we mention the rise in sea level, it is obviously more difficult to imagine. Globally, however, the Mediterranean is increasing by 44 millimeters per year. And by the end of the century, this increase could be of the order of one meter per year ”, alerts the scientific director of the Center on Climate Resilience, based at Eurecat Amposta.
Exacerbated by more frequent storms and unbridled concreteization, this rise in water levels has already resulted, since 2017, in a significant decline in certain metropolitan areas on the coast. With average setbacks of up to 9.8 meters per year in Badalona and 7.5 meters in Montgat. “According to the most favorable forecasts, by 2035, only 54% of the current beaches will still benefit from the conditions of width necessary for the provision of leisure services and 9% will be completely eroded”, insist the scientists who collaborated in the study.
Delivery of sand to the beaches
In addition to urban areas, deltas are particularly affected by erosion. At the mouth of the Ebro, researchers have observed wear on the coast of the order of 10 to 15 meters per year over the past decades. “To maintain themselves, these ecosystems need a supply of sediment to be made via rivers and streams”, details Carles Ibanez, who justifies their decline by the weakening of the flow of watercourses and by the impact of certain constructions such as ports or dams, which prevents the sand from being deported towards the sea. deficits, no less than 775,000 m3 of sand were transported each year, between 2002 and 2010, to Catalan beaches, mainly in Barcelona. A solution considered expensive, non-ecological, and above all difficult to sustain in the long term.
“Without a comprehensive policy, which incorporates a new way of approaching the management of rivers and the supply of sediment to the coasts, we will not solve the problem”, judges the scientist who is working in this capacity on a pilot project on the Ebro. A new approach that will not be successful without other actions, including ecosystem restoration. “For example, we need to return to Posidonia meadows. Present everywhere on the Catalan coast fifty years ago, these aquatic plants have largely disappeared under the effect of pollution and trawling ”, adds Purificacio Canals, president of the MedPAN association – network of managers of marine protected areas in the Mediterranean – which also coordinated the report. “Thanks to their roots, these seagrass beds can help hold the sand to the ground, which is more important when the waves are more violent. “
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