can be manipulated in such a way that the system will be forced back into a
durable state of mobility? Is this possible at all? The first restoration projects in
The Netherlands were aimed at restoring pioneer stages by sod cutting in dune
slacks (Grootjans et al. 2002; 2013). However, these kinds of measures are
designed to restore the existing pattern. Within a matter of years, the same method
has to be applied again, finally resulting in a lowering of the surface and a relative
increase in groundwater levels, wetter circumstances and at the end a fundamental
change of the system. Better results might be obtained if processes were restored,
resulting in the development of new dune slacks. In the last decade, several
experiments were started with the aim of restoring large-scale mobility. The main
idea is that if we succeed in restoring dune mobility, nature itself will keep
biodiversity at the same level, by creating freshly deflated valleys through deflation on the upwind side, with opportunities for pioneer species and destroying
climax vegetation by burial of sand on the downwind side (Arens et al. 2004).
With a certain percentage of mobile dunes within the area, permanent renewal of
pioneer stages and rejuvenation of the landscape are ensured.
7.5 Restoration of Aeolian Dynamics in Dunes
Restoration of aeolian dynamics in The Netherlands started at the end of the 1980s
with small-scale experiments on the island of Schiermonnikoog, in areas that
would in no way interfere with sea defense. In the 1990s the first blowouts were
reactivated (e.g., Van Boxel et al. 1997). Since then the scale and number of
experiments have increased. Restoration of blowouts resulted in a temporary
revitalization of aeolian dynamics. Only a small percentage of the reactivations
remained active after a period of years. Also, the area that benefited from the
interference was limited. The idea was that larger scaled restoration projects, like
the reactivation of parabolic dunes, would be more successful, since in the past
considerable effort was needed to stabilize them.
However, restoration of dune mobility turned out to be complicated. Monitoring
of these experiments indicates that restoration is not immediately successful
(Arens et al. 2004, 2005; Arens and Geelen 2006). After 15 years, with several
large-scale experiments, we can conclude that the removal of vegetation and soil is
not enough to restore large-scale landscape development. This type of interference
leads to a sudden and dramatic increase in aeolian dynamics (Fig. 7.8), but restabilization from root remnants causes important problems. The formation of a
desert pavement of blown out (dead) roots prevents further erosion. Thus far, most
reactivated areas have gradually declined in scale. Table 7.1 shows the stabilization rates for a number of projects in The Netherlands. For example, in the Van
Limburg Stirum area (Fig. 7.8) the former bare sand surface of 30 ha (1995) was
transformed into a mostly stabilized area alternated with 12 active blowouts and 18
freshly deflated surfaces. In 2009, 26 % of the original area was left bare, mostly
deflating. On the parabolic dune of the Verlaten Veld only six blowouts are left,
7 Restoration of Dune Mobility in The Netherlands
117
durable state of mobility? Is this possible at all? The first restoration projects in
The Netherlands were aimed at restoring pioneer stages by sod cutting in dune
slacks (Grootjans et al. 2002; 2013). However, these kinds of measures are
designed to restore the existing pattern. Within a matter of years, the same method
has to be applied again, finally resulting in a lowering of the surface and a relative
increase in groundwater levels, wetter circumstances and at the end a fundamental
change of the system. Better results might be obtained if processes were restored,
resulting in the development of new dune slacks. In the last decade, several
experiments were started with the aim of restoring large-scale mobility. The main
idea is that if we succeed in restoring dune mobility, nature itself will keep
biodiversity at the same level, by creating freshly deflated valleys through deflation on the upwind side, with opportunities for pioneer species and destroying
climax vegetation by burial of sand on the downwind side (Arens et al. 2004).
With a certain percentage of mobile dunes within the area, permanent renewal of
pioneer stages and rejuvenation of the landscape are ensured.
7.5 Restoration of Aeolian Dynamics in Dunes
Restoration of aeolian dynamics in The Netherlands started at the end of the 1980s
with small-scale experiments on the island of Schiermonnikoog, in areas that
would in no way interfere with sea defense. In the 1990s the first blowouts were
reactivated (e.g., Van Boxel et al. 1997). Since then the scale and number of
experiments have increased. Restoration of blowouts resulted in a temporary
revitalization of aeolian dynamics. Only a small percentage of the reactivations
remained active after a period of years. Also, the area that benefited from the
interference was limited. The idea was that larger scaled restoration projects, like
the reactivation of parabolic dunes, would be more successful, since in the past
considerable effort was needed to stabilize them.
However, restoration of dune mobility turned out to be complicated. Monitoring
of these experiments indicates that restoration is not immediately successful
(Arens et al. 2004, 2005; Arens and Geelen 2006). After 15 years, with several
large-scale experiments, we can conclude that the removal of vegetation and soil is
not enough to restore large-scale landscape development. This type of interference
leads to a sudden and dramatic increase in aeolian dynamics (Fig. 7.8), but restabilization from root remnants causes important problems. The formation of a
desert pavement of blown out (dead) roots prevents further erosion. Thus far, most
reactivated areas have gradually declined in scale. Table 7.1 shows the stabilization rates for a number of projects in The Netherlands. For example, in the Van
Limburg Stirum area (Fig. 7.8) the former bare sand surface of 30 ha (1995) was
transformed into a mostly stabilized area alternated with 12 active blowouts and 18
freshly deflated surfaces. In 2009, 26 % of the original area was left bare, mostly
deflating. On the parabolic dune of the Verlaten Veld only six blowouts are left,
7 Restoration of Dune Mobility in The Netherlands
117