Fields become coastal lagoon

A large area of reclaimed land on the Danish island of Funen has been returned to the sea. Experiences gained will assist municipalities in their future decisions about development of flood-prone land.

• First survey of its kind in the world

  Saturday 29 March 2014 marked an historic day in Northern Funen when several million tonnes of seawater flooded across 214 hectares of reclaimed arable land at Gyldensteen Strand. The flooding was not the consequence of a storm surge but an intentional step toward restoring this area to a lagoon, with eelgrass, bottom-dwelling algae, worms, snails, mussels, flatfish, marine birds and wading birds.

  

  Barnacle geese: The new inlet system is expected to attract breeding wading birds, gulls, terns, and, as here, barnacle geese. Photo: Viggo Lind

   

  The project, which is being backed by the Aage V. Jensen Naturfond, will serve various purposes. The primary purpose of the project is to restore one of Funen's most important bird areas. At the same time, researchers from the Department of Biology at the University of Southern Denmark will study how nature, the environment and climate change when inlets are restored on reclaimed arable land. This has never been studied before anywhere in the world, so the project and outcome are expected to draw international attention, as reclaims across the world are under threat from climate-change-induced sea-level rises. Finally, the researchers will carry out scientific surveys of ocean biodiversity both within and outside the area covered by the project.

   

• Drained land bought by foundation

  During the second half of the 19th century, many shallow inlets and marine areas were reclaimed for arable land throughout Denmark. This was in line with the saying of the time following the Danish loss of Schleswig-Holstein: "What has been lost externally, must be regained internally."

  
  However, the reclaimed land turned out to give only a poor yield. This was because the reclaims subsided, the sea breached the dykes and the reclaims were therefore often subject to flooding. During this period, the land was used for grazing and hay-making. Not until the 1960s, when effective pumps became available, could the areas be used for intensive cultivation.

   

  In February 2011, the Aage V. Jensen Naturfond bought a total of 616 hectares of the drained land from the Gyldensteen Estate, including the reclaimed areas of Gyldensteen Strand and Ore Strand (western part), as well as Lindholm and Langø, two former islands.

  
  In May 2012, North Funen Municipality adopted an EIA report and a supplement to its municipal plan, paving the way for the project at Gyldensteen Strand. Work commenced at the end of 2012 with the development of a carpark and footpaths. The process has involved moving more than a quarter of a million cubic meters of soil.

  

  Before the restoration. Map section: COWI

  
  

  After the restoration. Map section: COWI

   

• Experience for future generations

  After the planned opening of the dykes and flooding of the land at the end of March 2014, a comprehensive survey programme has been set in motion. Over the next seven years, researchers will be observing the development in flora and fauna composition, the exchange of nutrients and carbon dioxide between soil and water, as well as the exchange of nutrients between the lagoon and the surrounding sea.

   

  "Once the surveys have been completed in 2021, we anticipate that we will have gained unique knowledge about the biological and environmental developments in an area flooded after more than 140 years of intensive agricultural exploitation. This is knowledge that will be extremely valuable for us in future years when, according to every available calculation, seas will start to rise. The results from the project will help decision-makers when they need to assess whether flood-prone land should be saved by establishing more or larger dykes, or whether it should be flooded with seawater. This type of decision requires both biological, ecological, environmental and economic considerations," said Lars Malmborg, who works as a biologist with the Aage V. Jensen Naturfond.

  
  Biologists are not alone in having been allowed access to Gyldensteen Strand; the Aage V. Jensen Naturfond has also established more than 5 kilometers of footpaths and roads in the area for the public, as well as nature interpretation  facilities with class rooms for pupils.

• Better protection against climate change for the town of Bogense

  As a part of the ambitious project, the old dykes between Langø, Lindholm and Store Stegø have been removed. The 214-hectare area south of Lindholm is therefore once more joined to the sea as a shallow inlet surrounded by narrow salt meadows and reed beds.

   

  Around the new coastal lagoon, a total of 3.5 kilometres of new dyke have been established at spot height 3.0 DVR90, in order to safeguard the town of Bogense and countryside against flooding. These protection works include a dyke on the eastern tip of Store Stegø, down along the east side of the former island and onward along the Ålebækken watercourse until the watercourse passes under the bridge at the Gyldensteensvej road. From here, the dyke continues on the north side of the road in an eastern direction until it meets high ground. Furthermore, a dyke has been established along the west side of the road to Eriksholm on Langø. To ensure early protection of the dykes, these were sown with grass which will protect the dykes against the weather.

  

  Many people watched as the dykes were opened on 29 March 2014. Photo: Viggo Lind

   

• Nature and climate enriched

  With the flooding of Gyldensteen Strand, the area will once more become an important part of the original, shallow coastal waters of the Funen coast. The new inlet system is expected to attract breeding wading birds, gulls and terns, and in time the eastern shallow lake with reed beds will provide habitats for bitterns as well as spotted crake.

   

  Together with the freshwater wetlands to the east, the inlet system will make up an attractive area for geese, ducks and wading birds. The area could also attract more birds of prey such as peregrine falcons, white-tailed eagles and hen harriers. In time, the shallow coastal lagoon will evolve into a new, important habitat for marine biodiversity, including a wealth of small fishes and animals.

   

  Coastal lagoons like Gyldensteen Strand are important at global level,  because they store carbon. The coastal lagoon at Gyldensteen Strand is estimated to be able to store almost 2,000 tonnes of carbon annually, corresponding to 7,000 tonnes of carbon dioxide.

  

  Many people watched as the dykes were opened on 29 March 2014. Photo: Karsten Raulund-Rasmussen

• Broad cooperation a prerequisite

  The Aage V. Jensen Naturfond today owns around 18,000 hectares of natural areas in Denmark. The Foundation wants broad backing for its nature preservation efforts, so that these efforts may continue. The Foundation therefore always carries out its projects in cooperation with the authorities, green organisations and other stakeholders in terms of both planning, establishment and public use of the areas. This is also the case for this project.

   

  

  The new coastal lagoon after opening the dykes. Photo Viggo Lind

  
  

  Water from the Kattegat quickly flooded the new wetlands after the dykes were opened. Photo: Karsten Raulund-Rasmussen

• Facts about Gyldensteen Strand

  The coastal lagoon at Gyldensteen Strand has been restored on 214 hectares of land with an adjacent 16 hectares of coastal meadow. A total of 13 islands were established in the inlet to accommodate bird life. Three stretches of dyke totalling 700 meters were removed and the former Lindholm island was restored.

  
  A total of 3350 metres of new dykes have been established to protect the town of Bogense.

  
  A new shallow lake, Engsøen, has been established, including seven new islands. The lake measures 142 hectares with an average depth of 0.5 meters.

  
  Five new parking areas for visitors has been established, as well as two new parking areas for disabled visitors. Five kilometres of new roads and paths have been established. Eight new lookout towers and bird hides have or will be established. A large nature interpretation faciliy has been established at Eriksholm, including exhibitions, toilet facilities for the disabled and class rooms.