From the middle of the 1960s, improvements in road transport and the industrialisation of production in the south and east of France hurt the small regional producers who were also now experiencing European competition. It is from this date that the “Compagnie des Salins du Midi et des Salines de l’Est” (Company of salt works in the South and East) was created, with the aim of organising the monopoly in French salt production.

During the 1970s, a “salt war” took place in Europe. The trend for refined products and the reduction in cooking salt consumption as a conservation product led to a reduction in demand for salt “de terroir” and the failure of numerous traders in the Guérande basin. The most important were bought out by the “Compagnie des Salins du Midi et des salines de l’Est”, which opted for the disappearance of the western salt works, which were considered to be outdated and not profitable enough.

This situation led to a reduction in prices, the closure of numerous production sites and the disappearance of many companies. Guérande salt fell from favour, sales slumped and the salt marshes declined.