Silting threatened to render nature preserve Het Zwin increasingly dry and drive away all sorts of plant and bird species in the process. But thanks to a cooperative approach on the part of Belgium and the Netherlands, the watery nature is actually expanding now. 'Coastal birds stuff themselves here'.
The Zwin nature reserve in the Zeelandic-Flanders region is a tidal gully, an intertidal area where the seawater can reach the land via a channel in the dunes. At low tide, the area is above water; at high tide, much of it is submerged. 'As a result of the alternating between wet and dry, as well as between salt and fresh water and between clay and sand, the nature reserve is extremely varied', said Fred Schenk, who is in charge of the South district for Het Zeeuws Landschap ('Zeeland Landscape Foundation'). 'Without intervention, this channel would silt up and the mud flats and salt marshes would disappear'. Mud flats are areas of land without vegetation outside the dike that are flooded at high tide and where many species of worm, shrimp and shellfish live. When a mud flat silts up and consequently gets increasingly higher, it can turn into a salt marsh: a piece of land that does not flood during high tide but instead has many little streams meandering through it.
“The nature can be fully seen from many different vantage points via new hike and bike paths.”
The old Zwin covered 213 hectares. Schenk: 'Removing the international dike between the Zwin and the Belgian Leopoldpolder made it 120 hectares larger. That dike had been there since 1872. The Leopoldpolder has been 'returned' to nature, so to speak'. Of this new nature area, 110 hectares is in Belgium and 10 hectares in the Netherlands. The activities in the Zwin began in March 2016, carried out by the caretakers of the area: Het Zeeuws Landschap, the Province of West Flanders and Agentschap Natuur en Bos (the Belgian Nature and Forest Agency). 'Our neighbours to the south carried most of the load with respect to expansion', said Schenk. 'Now we are coordinating the management with each other. But the areas outside of the dike are managed by the sea more than anything else. The tidal movement is the most important form of management for the entire nature reserve. You can always have sheep or cattle graze salt marshes here and there, but additional steering is hardly necessary thanks to low and high tide. In this way, the nature that we cultivated has quickly become very pure again'.
But how exactly have the changes affected nature? 'The most important thing is that it is ebb and flow twice a day. Because the Leopoldpolder was already situated lower than the 'old' Zwin area, which had been elevated by sludge, it is now a wet, muddy place that quickly attracted small soil-dwelling creatures. When the tide goes out, shrimp and juvenile fish are left behind in the pools that remain, a buffet for the little egret, for example', said Fred Schenk. 'The creatures also now serve as a food source for birds that nest in the area, and for the thousands of birds that migrate through her in spring and autumn. Ducks, plovers, oyster catches and curlews are constantly coming and going; they all stuff themselves here'.
Bird islands were also created in the Zwin, Schenk explained: 'Many nesting coastal birds are struggling. It is becoming harder and harder to find a safe nesting place. Particularly for the tern species, such as the common tern, the little tern and even the Sandwich tern, but also for the Kentish plover and the ringed plover. These plovers are ground-nesting species, which prefer to be on shell beaches. Ground predators such as foxes and members of the weasel family can wreak havoc in coastal breeding colonies. But they cannot reach the islands and the birds are safe. This was taken into account when designing the area'.
According to Schenk, the transformation into a new habitat for a wide variety of flora and fauna is coming along at quite a pace. 'The Leopoldpolder was still freshwater last year but is now taking in salt water each day. As a result, the vegetation is also undergoing a huge transformation, from freshwater plants to salt-tolerant plants. Mudflats without vegetation provide opportunities for pioneering plants that are able to establish themselves fairly quickly thanks to the low and high tides. These plants – marsh samphire, sea aster and sea lavender – do need a certain amount of time during which the tide is receded in order to germinate and grow'.
As from this spring, the mouth of the Zwin is open to everyone; deeper into the nature reserve, the area is closed for the sake of the abundant bird life. During the summer months, Het Zeeuwse Landschap organises excursions here every week and by special appointment. That way, visitors can also explore the area 'from the inside' with a guide's supervision. 'Even including part of the area that floods during high tide', added Schenk. 'Furthermore, the nature can be fully seen from many different vantage points via new hike and bike paths.'