K. Falk et al., MARGRETHE-KOG AND THE ARTIFICIAL SALTWATER LAGOON - EVALUATION OF A HABITAT RESTORATION PROJECT IN THE DANISH WADDEN SEA, Environmental conservation, 21(2), 1994, pp. 133-144
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.