The area east of the village of Prosperpolder had been diked once before, long ago. During the Eighty Years' War in 1584, Dutch soldiers had deliberately breached the existing dikes as a strategic flooding - the same kind of inundation defense the Netherlands had used since the medieval period - and the great drowned land of Saeftinghe disappeared under salt water for the next three centuries. In the seventeenth century, methodical reclamation began again. The Hedwigepolder itself was completed in 1907, named for Duchess Hedwige de Ligne, and it was the last piece of land in the eastern corner of Zeelandic Flanders to be conquered from the sea. For 98 years, that conquest was permanent. Cows grazed where mussels had once attached themselves to oyster beds. Then Antwerp asked for something.

In 2005 the Netherlands and Belgium concluded four Scheldt Treaties, the centerpiece of which was a deepening of the Western Scheldt shipping channel to keep the port of Antwerp accessible to larger vessels. Because the European Union's Birds Directive and Habitats Directive required compensation for ecological damage from the deepening, the treaty obligated the Netherlands to create 600 hectares of new tidal nature outside the dikes. Studies under former minister Ed Nijpels concluded that the cheapest, most ecologically valuable site was Hedwigepolder. Flanders made clear it would pay for de-poldering Hedwigepolder, as the treaty specified, but not for more expensive alternatives. Work was supposed to start by the end of 2007.

The plan ran into a wall of opposition. The Provincial Council of Zeeland voted against it. The Dutch House of Representatives debated it furiously. Farmers and local politicians argued that giving back reclaimed land was a violation of everything the Netherlands stood for, that the dike had been built with Dutch sweat and should not be sacrificed for Belgian shipping. In April 2009 the Dutch Council of Ministers backed down, proposing instead to build new nature outside the existing dikes. The European Commission wrote a sharp letter doubting whether the alternative met the binding nature-restoration obligation. In July 2009 the Council of State temporarily prohibited the Scheldt deepening, warning that the natural features of the area might be affected. The port of Antwerp announced that if the work wasn't done by year's end, it would consider a claim of 70 million euros in annual damages. On 9 October 2009 the cabinet reversed itself and decided to proceed with de-poldering after all. The First Rutte cabinet then reopened the question in 2011 and proposed two smaller polders - Welzingepolder and Schorerpolder - as substitutes. Flanders objected. The European Commission objected. The argument went on for another decade.

In October 2022, after seventeen years of negotiation, court rulings, treaty disputes, and farmer protests, the dike was cut. Water rolled across the fields. The Hedwigepolder began the slow process of becoming tidal mudflat and salt marsh again, joining the adjacent Saeftinghe wetlands to form what is now one of the largest brackish tidal areas in Western Europe. Birds returned almost immediately - shelduck, avocet, redshank, spoonbill. The compensation requirement under the Habitats Directive was satisfied. The Scheldt deepening, by then long since completed, was finally on legally solid ground. The Antwerp container ships could pass at lower tides than before. The farmers had been bought out at full value, but value was not the point of their argument.

The Hedwigepolder dispute was never really about 295 hectares. It was about whether the basic deal between the Dutch and the water - we hold the land, you stay out - could be reopened to make room for shipping economics and European environmental law. For farmers whose families had worked reclaimed soil for generations, agreeing to give some of it back felt like the start of an unraveling. For environmentalists, it was overdue acknowledgment that the Western Scheldt estuary, choked by centuries of diking, had been quietly dying. Both arguments were correct. The polder is gone, and the marsh is rich. A new dike, the Nieuwe Sigmadijk, now protects the homes and villages that used to sit safely behind the old line. The sea has come back this far, and probably no further.