Influence on area and drying/exposure times

Influence on predator use

Sea-level rise is occurring naturally as the result of isostatic rebound following the last ice-age. The increasing land height in northern European areas is causing certain low areas, for example the eastern English coast, to sink relative to sea level. While nearshore subtidal mobile sandbanks will be less sensitive to this change, although greater depth will influence the wave climate and thus sedimentation patterns, intertidal sand and mudflats will be sensitive. Such a change will increase the ‘tidal-squeeze’ acknowledged for these area (Davidson et al, 1991). The inland movement of the low water region coupled with a fixed upper shore boundary, due to shore protection, produces that squeeze. Without restriction, sea level rise would move the high-water mark gradually further inland but this is prevented by the construction and maintenance of sea-walls. This reduction also affects the shore dynamics including its slope. In turn, this reduces the area available for colonisation by invertebrates and affects the feeding regime of wading birds and fishes.

The relationship between tidal depth over intertidal sand and mudflats dictates that any changes in tidal elevation by sea level rise or otherwise will therefore affect fish populations which in turn will affect the infaunal community. These changes may increase the time for feeding but reduce the area and hence the carrying capacity. The long term climactic changes resulting in sea level rise are outside the scope of this report although they may affect integrity of the biotope complexes. Reductions in the width of the intertidal habitats due to sea level rise will lower the carrying capacity of the area for wading bird populations. The size of the area available to birds may also influence the level of impact that a disturbance may have on a bird population (Davidson & Rothwell, 1993).

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