Wetenschap - 12 juli 2011

'Flooding Hedwige polder is really the only option'

Last month, State Secretary Henk Bleker decided the Hedwige polder in Zeeuws-Vlaanderen would not be returned to the sea, despite agreements with Belgium. 'That is unfortunate from an ecological point of view', says Tom Ysebaert of Wageningen Imares in Yerseke.

'The flooding of the Hedwige polder is one of the agreements made with Belgium in the Schelde Treaty. It was agreed that an extra 600 hectares of nature should be created in the Westerschelde to improve the area's safety. The channel to Antwerp has been made deeper and as a consequence the tide continues further up the river. The creation of more intertidal zones - land that is above water at low tide and under water at high tide - in the right places does not just mean more nature, it also has a beneficial impact on tidal behaviour. That is why 600 hectares of aquatic nature is needed along the Westerschelde, including 300 hectares in the Hedwige polder', concludes Ysebaert.

Bleker now wants to keep the Hedwige polder and flood other sections of land along the Westerschelde. Bleker's alternative consists of 'fragmented sites that probably don't add up to the area it was agreed to return to nature', says Ysebaert. 'They are now considering flooding land in the vicinity of Vlissingen, but this is a smaller site that had already been reserved as compensation for the container terminal in Vlissingen. There is also an advice to create nature outside of the dyke-protected areas, but I have my doubts about that. The expected benefit to nature of these measures is probably being overestimated. It certainly warrants further research.'
'Bleker's decision has deprived the flooding on the Belgian side of the border (of the Prosper polder) of much of its value. There was an opportunity to create one large nature reserve together with the Drowned Land of Saeftinghe. This could have been a suitable habitat for rare species. The salt marshes and mudflats could be home to birds and seals while serving as breeding grounds for fish and shrimps. Furthermore, it is easier to combine functions, such as nature experience, recreation and extensive forms of aquaculture, in such a large area.'

'The creation of more nature by the Netherlands and the Belgian province of Flanders was laid down in the European Birds and Habitats Directives. If we are to comply with those Directives, we need to create space for nature in the Westerschelde.'

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