Cuckmere Estuary Partnership

If the estuary were to become tidal again, the mudflats and saltmarsh that are already there would spread across the floodplain resulting in a mosaic of intertidal habitats. These intertidal mudflats and saltmarsh are rare and declining, but support internationally important communities of plants and animals.

The type of habitat that would be created depends on the relative land levels, and so how often it would be covered by the sea. If the land is very low it would flood on most tides and the predominant habitat would be mudflats. As the level gets higher so that land is exposed for two or three days in a month, pioneer saltmarsh plants like glasswort can develop. The higher the land, the less often it is covered by sea water, and so the number and diversity of plants increases. Once some vegetation has established, it helps to capture sediment left as the tide moves across it, building up land levels, allowing the saltmarsh to spread.

Measurements of land levels within the estuary indicate that much of the west side is high enough for glasswort to develop, whilst land on the eastern side of the river is much higher, especially around the meanders.

Mudflats

The environmental importance of mudflats should not be underestimated.

Whilst the species richness is relatively low – only about 20 species are found there including lugworms, ragworms, crustaceans, bivalves and snails – they occur in vast numbers. Because of this, mudflats are incredibly important as feeding grounds, particularly for birds that use them as refuelling stops when migrating between their breeding and wintering grounds. We know from other sites around the UK that the colonisation of new mudflats can be relatively rapid and this is reflected by bird usage; at Tollesbury and Orplands on the Essex coast, there was a high degree of bird usage within two years, and by five years after restoration, species richness was comparable to ‘natural’ areas.

Saltmarsh

Saltmarsh development is also likely to be rapid as there is a already a source of propagules within the site.

At Tollesbury, glasswort dominated lower marsh was present by the first winter after the breach, the higher marsh was established within two to four years, and the birds quickly adapted to the new conditions.

Bird populations on saltmarsh sites include wildfowl like shelduck who graze on the vegetation, and passerines like wheatear who feed on the seeds.

The Cuckmere already supports nationally important bird populations. If the estuary became tidal again, it is likely that we would see not only an increase in the number of birds using the area, but also an increase in the variety of species.

Intertidal estuaries act as nursery grounds for many fish species such as plaice and dab as well as feeding areas for sole, gobies, sea bass and flounder which feed on the worms, bivalve young and crustaceans. These may in turn attract ospreys and otters which are known to be present in the area.