5. maintaining or to achieve favourable conditions for all typical species.
Restoration projects comprise e.g. the recovery of Eel Grass (Zostera marina) and
mussel beds (Mytilus edulis and Ostrea edulis), and ecological restoration of
saltmarshes include de-embankment of summer polders and re-develop former
geomorphology and drainage systems. Restoration the widespread occurrence of
Zostera marina in the Netherlands is a real challenge, as the population at all
locations of restoration substantially decreased due to reduced seed production
(van Duren et al. 2013, 2014). Most likely, the water conditions, i.e. chemistry
and/or light are not adequate. Moreover, a fungus is threatening eel grasses. The
establishment of mussel beds (de Paoli et al. 2015) is a challenge too. Currently, the
possibility of using bio-degradable artificial reefs for mussel bank settlement is
studied in the Wadden Sea area. In contrary, restoration measures in saltmarshes
face higher success (Bernhardt and Koch 2003; Esselink et al. 2017). Salt marsh
restoration by habitat increase can be achieved via e.g. large scale de-embankment
(Wolters 2006). However, it can be assumed that restoration projects might become
more successful if major impacts, i.e. artificial limitation of natural dynamics, the
amount of nutrients and pollutants, will be reduced on regional or even global scale
in the future.
5.4 Restoration Projects of Coastal Dunes
Active dunes and wet dune slacks in general represent areas of positive sedimentation rates. Under natural conditions unvegetated dunes are migrating due to erosion
at one side and sedimentation at the other. Later succession stages of dunes show
more or less dense vegetation cover, i.e. pioneer vegetation, vegetation dominated
by grasses and herbs, dune shrubs, and finally forest if the airborne content of salt is
low enough.
Lithgow et al. (2013) defined and assessed variables influencing the success of
restoration measures in dune areas. They used different criteria and subcriteria such
as degree of degradation, system fragmentation, stress factors, factors that facilitate
restoration, and 38 indicators such as visitor pressure, infrastructure affecting sediment dynamics, and so on.
Restoration of coastal dunes and beaches including wet dune slacks has many
goals, facets, and mechanisms. Correspondently, the natural heterogeneity of dune
systems and the special conditions including human influences of each site needs to
be assessed. Numerous restoration projects showed that anthropogenic influences
cannot completely be compensated with respect to natural conditions including
hydrology, biodiversity and aeolian transport of sand, for example. Thus, also the
re-introduction of traditional management technics such as mowing, grazing, sod
removal and non-traditional construction of artificial habitats such as wet dune
slacks might be tested and evaluated (Grootjans et al. 2002).
298
C. Hobohm et al.
Restoration projects comprise e.g. the recovery of Eel Grass (Zostera marina) and
mussel beds (Mytilus edulis and Ostrea edulis), and ecological restoration of
saltmarshes include de-embankment of summer polders and re-develop former
geomorphology and drainage systems. Restoration the widespread occurrence of
Zostera marina in the Netherlands is a real challenge, as the population at all
locations of restoration substantially decreased due to reduced seed production
(van Duren et al. 2013, 2014). Most likely, the water conditions, i.e. chemistry
and/or light are not adequate. Moreover, a fungus is threatening eel grasses. The
establishment of mussel beds (de Paoli et al. 2015) is a challenge too. Currently, the
possibility of using bio-degradable artificial reefs for mussel bank settlement is
studied in the Wadden Sea area. In contrary, restoration measures in saltmarshes
face higher success (Bernhardt and Koch 2003; Esselink et al. 2017). Salt marsh
restoration by habitat increase can be achieved via e.g. large scale de-embankment
(Wolters 2006). However, it can be assumed that restoration projects might become
more successful if major impacts, i.e. artificial limitation of natural dynamics, the
amount of nutrients and pollutants, will be reduced on regional or even global scale
in the future.
5.4 Restoration Projects of Coastal Dunes
Active dunes and wet dune slacks in general represent areas of positive sedimentation rates. Under natural conditions unvegetated dunes are migrating due to erosion
at one side and sedimentation at the other. Later succession stages of dunes show
more or less dense vegetation cover, i.e. pioneer vegetation, vegetation dominated
by grasses and herbs, dune shrubs, and finally forest if the airborne content of salt is
low enough.
Lithgow et al. (2013) defined and assessed variables influencing the success of
restoration measures in dune areas. They used different criteria and subcriteria such
as degree of degradation, system fragmentation, stress factors, factors that facilitate
restoration, and 38 indicators such as visitor pressure, infrastructure affecting sediment dynamics, and so on.
Restoration of coastal dunes and beaches including wet dune slacks has many
goals, facets, and mechanisms. Correspondently, the natural heterogeneity of dune
systems and the special conditions including human influences of each site needs to
be assessed. Numerous restoration projects showed that anthropogenic influences
cannot completely be compensated with respect to natural conditions including
hydrology, biodiversity and aeolian transport of sand, for example. Thus, also the
re-introduction of traditional management technics such as mowing, grazing, sod
removal and non-traditional construction of artificial habitats such as wet dune
slacks might be tested and evaluated (Grootjans et al. 2002).
298
C. Hobohm et al.