MARGRETHE-KOG AND THE ARTIFICIAL SALTWATER LAGOON - EVALUATION OF A HABITAT RESTORATION PROJECT IN THE DANISH WADDEN SEA

Across the Danish-German border in the Wadden Sea, a new dike was comp leted in 1981, enclosing formerly productive tidal flats and marsh are as which were most important as feeding grounds to breeding and migran t waterbirds. The bird populations responded immediately by a 50% or m ore reduction in numbers of resting birds and breeding pairs of most s pecies. This paper reviews the management of the enclosed areas, compa ring the differences in approach in the Danish and German areas involv ed. Most importantly, a saline enviroment was re-established (a Saltwa ter Lagoon) in parts of the Danish area by actively pumping in water f rom the Wadden Sea. Despite sometimes drastic fluctuations in environm ental conditions in the Lagoon to some extent counteracted the negativ e effects of the dike construction. The former marsh areas on the Dani sh side are drained and partly cultivated. In addition, the land areas are separated from the Lagoon by a dike, preventing a saline environm ent from being maintained outside the designated Saltwater Lagoon. Ove rall, the land areas in the Danish part are too dry and intensively us ed to be optimal to the breeding birds. After construction of the dike , the breeding bird populations shifted more towards the German areas. Here, the land-use is much more beneficial to the breeding birds, bec ause no cultivation has taken place, and a generally high water-level in the marsh areas is preserved. Furthermore, in Germany the new dike was placed closer to the original coastline than in Denmark, but a sma ll area of the original foreland remained outside the dike, povinding good breeding sites for colonial waterbirds. It is concluded that, due to the creation of the Saltwater Lagoon, the Danish part of the area again sustains waterbirds in numbers of international importance. But an integrated approach to the Nature management of the enclosed areas - combining the solutions adopted for land management in the German pa rt with the technical solution of re-establishing a saline environment behind the dike as in the Danish part - would have rendered a better compensation for the damage caused by the dike construction and relate d activities.