Saltmarsh vegetation - State 4, abandoned

Saltmarshes formerly grazed by domestic stock but where this has been abandoned present a series of conservation problems. The most important is the rapid growth of the courser grasses which takes place once grazing pressure is reduced. These have been described in some detail for saltmarshes in Holland and around the Baltic Sea where abandonment has occurred at many sites (Dijkema 1990). A more detailed review of the situation on the Wadden island of Schiermonnikoog showed how Elymus athericus became dominant after 5-20 years on mature marshes, slightly longer on younger marshes (van Wijnen et al. 1996). Other examples include some parts of the Bridgwater Bay, Somerset, England (see picture below) and in the Wash, Norfolk, England.

Caption: Overgrown ungrazed saltmarsh dominated by sea aster Aster tripolium, sea couch Elymus athericus and red fescue Festuca rubra, Bridgwater Bay, Somerset.

In the brackish marshes of the Baltic reduction in cattle grazing led to the rapid spread of competitive species such as Phramites australis and a decline in species richness and structural diversity of the saltmarsh (Lundberg 1996).

Caption: Moderately grazed and ungrazed saltmarsh in Bridgwater Bay. The picture above shows more detail of the ungrazed saltmarsh on the far side of the fence in the picture on the right.

Comment: The overall impact of abandonment of grazing is to reduce the value of the marsh, especially from a nature conservation perspective.

References

Dijkema, K.S. 1990. Salt and brackish marshes around the Blatic Sea and adjacent parts of the North Sea. Biological Conservation, 51., 191-209.

Lundberg, A. 1996. Changes in the vegetation and management of saltmarsh communities in southern Norway. In: Studies in European Coastal Management, eds.Jones, P.S., Healy, M.G. & Williams, A.T.Samara Publishing Ltd., Cardigan, 197-206. Abstract...

van Wijnen, H.J., Bakker, J.P. & Vries, Y. 1996. Twenty years of saltmarsh succession on a Dutch barrier island. Journal of Coastal Conservation, 3/1., 9-18.