The researchers studied how sediment on the Western Gulf of Lions shoreface in France has changed over the 20th century. They used advanced methods to track the amount of sand and how it moved along the coast. The results show that the volume of sand has decreased significantly over the years, with erosion becoming more dominant in recent decades. This is mainly due to less sand coming from rivers and human activities removing sand from the coast. The study suggests that erosion will likely continue in the future, leading to a gradual depletion of the available sand reservoirs.