Field survey using the National Vegetation Classification (NVC) methodology (Rodwell, 2000) was used to record and map the vegetation of saltmarsh and other habitats within the Essex Estuaries candidate Special Area of Conservation (cSAC) from July to October 2001 and 2002. Saltmarshes were surveyed at the major estuaries of the Colne, Blackwater, Crouch and Roach and the open coast tidal flats at Foulness and Dengie. This report presents the survey results for these sites.
The Essex survey forms part of a wider study of The Wash, North Norfolk Coast and Essex Estuaries cSACs. The main aim of this project is to provide detailed NVC descriptions of the European sites, which will allow a baseline to be established for future monitoring purposes.
Within the Essex Estuaries, most of the saltmarsh vegetation has not been surveyed since 1974, and the data from this and preceding surveys were incorporated into âThe Saltmarsh Survey of Great Britainâ (Burd, 1989), which provided a basis for selecting Sites of Special Scientific Interest (SSSIs). However, this data is unsuitable for monitoring sites that are recognised for their international importance. Furthermore, âThe Saltmarsh Survey of Great Britainâ classification is not convertible into National Vegetation Classification (NVC) communities and rare and unusual saltmarsh communities were not described or mapped. Hence, there is a need for systematic vegetation species information and in particular, mapping of saltmarsh communities.
In total, 860 quadrats were recorded during the 2001/2002 survey season and used to construct floristic tables describing the vegetation communities. Target notes were also recorded for various parameters including management practice, drainage and evidence of erosion and or deposition. The survey results were used in conjunction with aerial photographs of The Essex Estuaries in order to enhance the mapping output. The vegetation communities and sub-communities were mapped at 1:5000 scale in broad accordance with the colour coding used in the âNVC Survey of Saltmarsh Habitat in the Severn Estuaryâ (Dargie, 1998a and 1998b). However, it was necessary to expand the range of colours in order to accommodate the large number of vegetation communities and sub-communities present. In addition to this, during 2002, 13 monitoring transects were established and sampled.
The Essex saltmarshes are distributed around the estuaries, in varying size patches. In the sheltered areas within the estuaries, the build up of sediments creates the conditions required for saltmarsh development. Saltmarshes border the upper shores and display a range of vegetation which varies according to tolerance to tidal flooding. The Essex Estuaries European marine site contains approximately 8% of the UK saltmarsh resource (about 3,500 hectares). The habitats within the saltmarshes are of enormous conservation value not only because of the wide variety of saltmarsh plant communities, which occur, but also for the invertebrates and particularly for the vast numbers of breeding and overwintering waterfowl.
There are areas of mudflats exposed at low tides which are interspersed with patches of SM6 Spartina anglica. The edges of the marshes generally have a cliff face of a few centimetres to a metre, and these have SM8 Annual Salicornia pioneer community in places. The most extensive mosaics comprise a mix of SM14 Atriplex portulacoides/SM13 Puccinellia maritima sub-communities. Throughout Essex there are swathes of SM24 Elytrigia atherica which occur along the seawalls, with occasional patches of SM26 Inula crithmoides. The SM25 Suaeda vera drift-line community is occasionally present along the base of the seawalls.