Keywords:
artificial island
sand nourishment
habitat development
Contact: Dr. Klaus Janke, Head of the ‘National
Park Hamburg Wadden Sea’, Billstr. 84, 20539 Hamburg.
Location: Germany, Hamburg Wadden Sea, estuary of
the Elbe
National Park Hamburg Waddensee
The National Park Hamburgisches Wattenmeer with a surface measure
of ca. 11,700 ha is situated in the estuary of the river Elbe.
It exists as a National Park since 1990 and includes the islands
Neuwerk, Scharhoern and Nigehoern. Scharhoern is one of the most
important breeding island for terns and other seabirds in the
whole region of the Wadden Sea. The development of a dune vegetation
has been artificially supported and added by installing bush fences
to catch the drifting sand next to the island since 1926. In 1973
the island reached its largest extension covering more than 18
ha of the Scharhoern plate. Since then, it has been shrinking
rapidly. Following the sedimentation transport affected by wind
and sea, the island has drifted 1.4 km eastward during the last
century and got closer to the deep fairway of the Elbe.
Management
Because of the threatening loss of the breeding sanctuary Scharhoern,
the environmental authority of Hamburg decided in 1989 to establish
a new dune island by sand nourishment 1.5 km away in the southwest
of Scharhoern but still situated on the Scharhoern reef: the artificial
island Nigehoern. The activities started in June 1989. Using a
2.5 km long pipeline, 1.3 mill. m³ sediment was pumped up
the Scharhoern-plate within a time span of 5 weeks. When sculpturing
the topography of the surface, the typical look of a low dune
island in the estuary of the river Elbe was imitated: the initial
form was a circle covering about 30 ha. This was supported by
concentric bush fences at the periphery, a double circle of bush
fences at the edge and also three parallel bush-fence lines in
the center of the island. Latter ones were built to promote the
development of primary dunes. The mean height of the new island
was 4.25 m above sealevel, reaching 5.2 m on the top of the dunes.
In late summer of 1991 a kidney shaped reef was washed up in the
northwest of the island to protect it from strong sea erosion.
To support the sand nourishment and the effect of the bush fences,
and to minimize eolic sediment drift on the island, high activities
in sowing and planting dune vegetation (mainly Elymus arenarius,
Ammophila arenaria and Agropyron junceum) have taken
place.
Results
The attempt to establish a bird-protecting-island with natural
features has succeeded. In the area of the bush fences the vegetation
of white dunes has developed successively, in the edge of the
island vegetation of drift line communities appeared as well as
of salt marshes. Already in the first spring after preparing
the island, Nigehoern was colonized by breeding sea birds. From
1990 it was the prefered breeding area for little terns ( Sterna
albifrons) and kentish plovers (Charadrius alexandrinus),
followed by arctic tern (Sterna paradisaea) and common
tern (Sterna hirundo). In 1996 the whole colony of sandwich
tern (Sterna sandvicensis) had moved to Nigehoern. Furthermore
the new island had developed into an important resting area for
the little tern (Sterna albifrons) and to an important
moulting place for the barnacle goos (Branta leucopsis)
The National Park Hamburg Wadden Sea in the Elb estuary
References
- Janke, K. & D. Glitz (1992): The story of Nigehoern.
Wadden Sea Newsletter 1: S. 8-14
- Janke, K. (1996): Sieben Jahre Insel Nigehoern: Laesst sich
die Aufspuelung einer Vogelschutzinsel mit den Naturschutzzielen
des Nationalparkes Hamburgisches Wattenmeer vereinbaren ?. Schriftenreihe
Nationalpark Niedersaechsisches Wattenmeer. Band 2: S. 49-53
