pre-marram 1950s barrier morphology (see Hilton et al. 2005). Clearly, it has been
advantageous to have an understanding of the impact of marram on barrier
development in setting restoration goals and interpreting landform change following the initial herbicide operations. It has been possible to account for and
justify the destabilization of the barrier, the first step in re-establishing a dune
system with transgressive dune elements, albeit at the expense of downwind
wetlands and other ecosystems.
5.6 Discussion and Conclusion
The motivation to ‘‘restore’’ dunes in the cases presented was twofold. In the North
Island cases, local authorities sought to re-establish a stable foredune that was
foremost, a more naturally functioning foredune with native species, that was
aesthetically pleasing, and that provided some protection from storm-forced episodic erosion. The scope of the restoration was constrained by the small accommodation space and sediment supply. In contrast, the Rakiura National Park,
Stewart Island, operations were motivated by a desire to re-establish the natural
character of dune systems dominated by transgressive dune forms, low species
diversity, and high dynamism. The accommodation space is not limiting and
concerns about the downwind impact of marram eradication have been addressed.
At Doughboy Bay a progradational sequence of foredunes had developed in
association with marram grass where none had previously existed. There is now an
understanding that the operations will liberate sand and some loss of downwind
habitats, in part an artifact of marram invasion, will be lost. For example, a
wetland dominated by jointed wire rush (Leptocarpus similis) developed as the
barrier prograded to the north in Doughboy Bay. This wetland will soon be
inundated by sand.
There is clearly a need to adopt a long-term perspective in all such restoration
projects. The Department of Conservation might have hoped that the eradication of
marram grass from Doughboy Bay would take well under a decade. In fact,
complete eradication may not be achieved before 2015, 15 years after the program
commenced. It could take longer, depending on the longevity of buried marram
grass seed. The presence of a viable marram grass seed bank, two rhizome
stranding events (2005 and 2008) and the inclement weather have all delayed the
completion of the project. This is hardly surprising, given that the Doughboy
operation was the first, large-scale operation of its type. In the case of Oakura, the
dynamics of this sediment-starved beach are having a significant effect on the
stability and longevity of the reconstructed foredune, and a lack of weed maintenance and planting of intermediate species by the Council authorities has
resulted in a decline in the natural ecological value of the foredune.
These three studies demonstrate the need for conservation managers to adopt a
long-term management perspective, the great importance and role of monitoring,
and action following monitoring. The MEP on Stewart Island will be achieved
5 Restoration of Foredunes and Transgressive Dunefields
89
advantageous to have an understanding of the impact of marram on barrier
development in setting restoration goals and interpreting landform change following the initial herbicide operations. It has been possible to account for and
justify the destabilization of the barrier, the first step in re-establishing a dune
system with transgressive dune elements, albeit at the expense of downwind
wetlands and other ecosystems.
5.6 Discussion and Conclusion
The motivation to ‘‘restore’’ dunes in the cases presented was twofold. In the North
Island cases, local authorities sought to re-establish a stable foredune that was
foremost, a more naturally functioning foredune with native species, that was
aesthetically pleasing, and that provided some protection from storm-forced episodic erosion. The scope of the restoration was constrained by the small accommodation space and sediment supply. In contrast, the Rakiura National Park,
Stewart Island, operations were motivated by a desire to re-establish the natural
character of dune systems dominated by transgressive dune forms, low species
diversity, and high dynamism. The accommodation space is not limiting and
concerns about the downwind impact of marram eradication have been addressed.
At Doughboy Bay a progradational sequence of foredunes had developed in
association with marram grass where none had previously existed. There is now an
understanding that the operations will liberate sand and some loss of downwind
habitats, in part an artifact of marram invasion, will be lost. For example, a
wetland dominated by jointed wire rush (Leptocarpus similis) developed as the
barrier prograded to the north in Doughboy Bay. This wetland will soon be
inundated by sand.
There is clearly a need to adopt a long-term perspective in all such restoration
projects. The Department of Conservation might have hoped that the eradication of
marram grass from Doughboy Bay would take well under a decade. In fact,
complete eradication may not be achieved before 2015, 15 years after the program
commenced. It could take longer, depending on the longevity of buried marram
grass seed. The presence of a viable marram grass seed bank, two rhizome
stranding events (2005 and 2008) and the inclement weather have all delayed the
completion of the project. This is hardly surprising, given that the Doughboy
operation was the first, large-scale operation of its type. In the case of Oakura, the
dynamics of this sediment-starved beach are having a significant effect on the
stability and longevity of the reconstructed foredune, and a lack of weed maintenance and planting of intermediate species by the Council authorities has
resulted in a decline in the natural ecological value of the foredune.
These three studies demonstrate the need for conservation managers to adopt a
long-term management perspective, the great importance and role of monitoring,
and action following monitoring. The MEP on Stewart Island will be achieved
5 Restoration of Foredunes and Transgressive Dunefields
89