8 Biological and Physical Processes That Affect
Saltmarsh Erosion and Saltmarsh Restoration:
Development of Hypotheses
R.G.HUGHES
8.1 Introduction
Saltmarsh habitats are under increasing threat, particularly from sea-level
rise (SLR) associated with global warming and increased wave action associated with climate change. The saltmarshes of southeastern England, which
developed for several centuries under conditions of local SLR, are now
disappearing rapidly. These marshes offer the potential for study of the processes that determine loss of vegetation, and of the processes necessary for the
managed amelioration of these losses, as some experimental managed realignment schemes are in progress. Burd (1992) reported that, in the 15 years
prior to 1988, the total losses of saltmarsh vegetation in the estuaries of southeastern England, from the River Orwell in Suffolk to the Swale in Kent, varied
from 23 % in the Blackwater to 44 % in the Stour (Fig. 8.1). Most of the losses
were from the pioneer zone where up to 74% was lost during the same period.
Loss of these marshes is causing concern because of the reduction in protection offered by the vegetation to the sea walls that surround most of this
coastline, and because of the conservation importance of these habitats. These
estuaries contain about 28,000 ha of mudflats and 8500 ha of vegetated saltmarshes, of which about 85 % is internationally important, largely because of
their use by migrating and overwintering birds.
Enclosure of saltmarshes behind sea walls, primarily for agricultural use,
has occurred in these estuaries for several centuries (e.g. Burd 1995). While
these losses are attributable, the recent erosion is less easy to explain. Some
factors that may contribute to saltmarsh loss include; removal of sediment by
dredging, which may increase exposure to wave action; distant sea walls and
groynes, which may limit erosion and transport of recharging sediment; and
adjacent sea walls, which may accelerate local erosion by altering tidal flow
and by reflecting wave energy back across the fronting saltmarsh. The loss
of most of the intertidal eelgrass Zostera marina because of the wasting
phenomenon from the 1930s, may have increased sediment erosion in front of
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
Saltmarsh Erosion and Saltmarsh Restoration:
Development of Hypotheses
R.G.HUGHES
8.1 Introduction
Saltmarsh habitats are under increasing threat, particularly from sea-level
rise (SLR) associated with global warming and increased wave action associated with climate change. The saltmarshes of southeastern England, which
developed for several centuries under conditions of local SLR, are now
disappearing rapidly. These marshes offer the potential for study of the processes that determine loss of vegetation, and of the processes necessary for the
managed amelioration of these losses, as some experimental managed realignment schemes are in progress. Burd (1992) reported that, in the 15 years
prior to 1988, the total losses of saltmarsh vegetation in the estuaries of southeastern England, from the River Orwell in Suffolk to the Swale in Kent, varied
from 23 % in the Blackwater to 44 % in the Stour (Fig. 8.1). Most of the losses
were from the pioneer zone where up to 74% was lost during the same period.
Loss of these marshes is causing concern because of the reduction in protection offered by the vegetation to the sea walls that surround most of this
coastline, and because of the conservation importance of these habitats. These
estuaries contain about 28,000 ha of mudflats and 8500 ha of vegetated saltmarshes, of which about 85 % is internationally important, largely because of
their use by migrating and overwintering birds.
Enclosure of saltmarshes behind sea walls, primarily for agricultural use,
has occurred in these estuaries for several centuries (e.g. Burd 1995). While
these losses are attributable, the recent erosion is less easy to explain. Some
factors that may contribute to saltmarsh loss include; removal of sediment by
dredging, which may increase exposure to wave action; distant sea walls and
groynes, which may limit erosion and transport of recharging sediment; and
adjacent sea walls, which may accelerate local erosion by altering tidal flow
and by reflecting wave energy back across the fronting saltmarsh. The loss
of most of the intertidal eelgrass Zostera marina because of the wasting
phenomenon from the 1930s, may have increased sediment erosion in front of
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001