Chris Bakker, It Frysk Gea Peter Esselink, bureau Puccimar
September 2015
Nature restoration and management of saltmarshes at the Wadden Sea coast
Mainland salt marshes at the Wadden sea coast
eiland vasteland
areaal (km2 )
50 100 150 200 250
NL D DK
island mainland area (km2)
22,5 km2
Zonation at the salt-marsh
Salt marsh
Summer polder
Intertidal area
Decrease in mainland salt marshes
year
1600 1700 1800 1860 1925 1995 2008
area (km2 )
0 20 40 60 80 100 120 140 160
A man-made salt marsh
Sea aster
Barnacle goose
Avocet
Common tern
What is the problem?
•
Too little habitat for birds, plants•
Lack of gradients•
Habitat quality sub-optimal•
Lack of accretion in the face of sea level rise Two experiments:•
Saltmarsh restoration by de-embankment•
Grazing experimentsExperiment 2001 de-embankment
Main measures: - three breaches in the seaward summer bank
2001 - digging artificial creeks; rewetting by filling of ditches - continuation of livestock grazing
Accretion problem in a nutshell
time (years after de-embankment)
0 2 4 6 8 10
depth (mm)
0 40 80 120 160 200
0 2 4 6 8 10
station 4
creek near breach far creek far breach far station 3
grazed n = 4 ungrazed n = 3
Accretion rates
Restoration site catches up with Sea Level Rise
brackish-marsh vegetation secondary pioneer vegetation
low-marsh vegetation high-marsh vegetation
fresh grassland
year 10 year 7 year 1
Fresh grass replaced by salt marsh vegetation
© J. de Vlas
HIGH ELEVATION LOW ELEVATION
High impact of grazing
Grazing leads to soil compaction
Effects on birds
Redshank Barnacle goose
Avocet Oystercatcher
Lessons learned de-embankment
•
After de-embankment salt-marsh accretion can compensate sea level rise•
Vegetation salt-marshes returned rapidly•
Grazers compacted soil and induced secondary pioneer vegetation•
Area became less attractive for breeding birds•
At this salt-marsh a step-wise de-embankment may be the best management optionGrazing experiment
Grazing effects on vegetation
Intensively grazed Moderately grazed
Not grazed
Short term
Long term
Voles
Birds: mixed picture
Trampling effect of grazers
Flowers and insects
Not one single recipe, but a mosaic
Next stept for management
•
Continue de-embankment in a step-wise approach•
Strive for a mosaic of grazing regimes•
First project: sweet-salt gradient inconjunction with a freshwater discharge at this saltmarsh
Acknowledgements
