effect that no plants can grow where the visitor impact on sandy ground is high. On
the other side, behind the fence dense and often shrubby vegetation occurs. The
natural sequence of succession stages cannot be observed under such circumstances.
In some dune areas, it is a successful policy to tolerate trespassing fences.
Recent approaches along European dune systems focus on returning the natural
dynamics and homogeneity in the landscape (Grootjans et al. 2002; Provoost et al.
2011). Artificial blow outs are created, or even entire dunes are removed to open up
the coast line. In some cases, on islands, the opening of dunes facilitates wash-overs
to occur, sea water flowing through the dunes into the saltmarshes on the other side
of the dune system, increasing a potential for nature. Where sand was once fixed, it is
now mobile and can reach weaker dune complexes through natural processes,
increasing the overall resilience of the dunes. Artificial blow-outs may provide
new sources of sand to rejuvenate coastal grasslands and provide space for flora
and fauna that need open areas (Aggenbach et al. 2018). In suitable areas, new dunes
or new sand flats are being created on the coastline, sometime referred to as sand
engines. In other cases, sand is added to the beach. This so-called sand suppletion
functions as a source of sand for natural dune areas and provide new space for beach
communities.
Although many coastal dune restoration projects have been evaluated as successful with respect to target species, target communities, elimination of anthropogenic
residues and elimination of exotic species or woody plants (e.g. Petersen 1999;
Grootjans et al. 2002; Ruz et al. 2005; Nygaard et al. 2011; Martínez et al. 2013;
Lithgow et al. 2013; Eischeid et al. 2018), it is still unclear and debatable how
effective the various measurements in dune systems at the long term might be. This
could apply to the introduction of large grazers and the creation of blowouts. It is
quite possible that the re-introduction of extensive traditional management techniques, such as mowing, grazing, sod removal and rewetting dune slacks, will be
necessary in the long term (Grootjans et al. 2002). The difficulty lies in the elemental
drivers of the dune system: water and wind. These drivers seem to be part of a much
larger system subject to climate variables and weather conditions. There are indications of large cyclic events that affect atmospheric and oceanic currents (for instance
El Niño, or the North Atlantic Oscillation), having an effect on local and regional
aeolian processes in dune systems. Artificial measurements that intend to restore the
fundamental dynamics of dunes should take the complex interactions in consideration (González-Villanueva et al. 2013; Van Rooijen et al. 2018).
5.5 Restoration Projects of Rocky Shores
Rocky shores are generally no subject for habitat restoration, as they simply perform
just as they are, as long as their existence is guaranteed. An interesting item,
however, with respect to the ‘restoration’ of rocky shores and their species, is the
construction of artificial structures, which may facilitate a high biodiversity. As an
example, a remarkable project is that of the Afsluitdijk in the north of the
300
C. Hobohm et al.
the other side, behind the fence dense and often shrubby vegetation occurs. The
natural sequence of succession stages cannot be observed under such circumstances.
In some dune areas, it is a successful policy to tolerate trespassing fences.
Recent approaches along European dune systems focus on returning the natural
dynamics and homogeneity in the landscape (Grootjans et al. 2002; Provoost et al.
2011). Artificial blow outs are created, or even entire dunes are removed to open up
the coast line. In some cases, on islands, the opening of dunes facilitates wash-overs
to occur, sea water flowing through the dunes into the saltmarshes on the other side
of the dune system, increasing a potential for nature. Where sand was once fixed, it is
now mobile and can reach weaker dune complexes through natural processes,
increasing the overall resilience of the dunes. Artificial blow-outs may provide
new sources of sand to rejuvenate coastal grasslands and provide space for flora
and fauna that need open areas (Aggenbach et al. 2018). In suitable areas, new dunes
or new sand flats are being created on the coastline, sometime referred to as sand
engines. In other cases, sand is added to the beach. This so-called sand suppletion
functions as a source of sand for natural dune areas and provide new space for beach
communities.
Although many coastal dune restoration projects have been evaluated as successful with respect to target species, target communities, elimination of anthropogenic
residues and elimination of exotic species or woody plants (e.g. Petersen 1999;
Grootjans et al. 2002; Ruz et al. 2005; Nygaard et al. 2011; Martínez et al. 2013;
Lithgow et al. 2013; Eischeid et al. 2018), it is still unclear and debatable how
effective the various measurements in dune systems at the long term might be. This
could apply to the introduction of large grazers and the creation of blowouts. It is
quite possible that the re-introduction of extensive traditional management techniques, such as mowing, grazing, sod removal and rewetting dune slacks, will be
necessary in the long term (Grootjans et al. 2002). The difficulty lies in the elemental
drivers of the dune system: water and wind. These drivers seem to be part of a much
larger system subject to climate variables and weather conditions. There are indications of large cyclic events that affect atmospheric and oceanic currents (for instance
El Niño, or the North Atlantic Oscillation), having an effect on local and regional
aeolian processes in dune systems. Artificial measurements that intend to restore the
fundamental dynamics of dunes should take the complex interactions in consideration (González-Villanueva et al. 2013; Van Rooijen et al. 2018).
5.5 Restoration Projects of Rocky Shores
Rocky shores are generally no subject for habitat restoration, as they simply perform
just as they are, as long as their existence is guaranteed. An interesting item,
however, with respect to the ‘restoration’ of rocky shores and their species, is the
construction of artificial structures, which may facilitate a high biodiversity. As an
example, a remarkable project is that of the Afsluitdijk in the north of the
300
C. Hobohm et al.