The ageing of saltmarshes
The first stages of vegetation succession are becoming less common on the saltmarshes of Zeeland.
Trends
Under natural conditions, in some places saltmarshes grow by accretion, and elsewhere they shrink because of erosion. The damming of tidal inlets in the Zeeland delta, the empoldering of land, and the deepening of the navigation channel in the Westerschelde are making it increasingly difficult for new saltmarshes to form, so the area of saltmarsh in the Zeeland delta is dwindling.
Because few new saltmarshes are forming and the vegetation of the existing ones is becoming ranker as a result of vegetation succession, the first stages of vegetation succession are becoming increasingly uncommon. This can be seen from the decline in Townsend's cord-grass (a pioneer species) and the increase in sea couch-grass (a more rank species) in Saeftinge (see figure).
Technical note
The map shows the change in the vegetation of saltmarshes on the Verdronken Land van Saeftinge between 1971 and 1992, as illustrated by the distribution of Townsend's cord-grass and sea couch-grass. The saltmarshes of Saeftinge account for 80% of the saltmarsh area in the Zeeland delta.
References
- Dijkema, K.S. (1987). Changes of salt-marsh area in the Netherlands Wadden Sea after 1600. In: A.H.L. Huiskes, C.W.P.M. Blom en J. Rozema (eds) Vegetation between land and sea. Junk, Dordrecht: pp. 42-49.
- Dijkema, K.S., J.H. Bossinade, A. Nicolai, H. Jongerius, J. Frankes, K. Haan. P. Leusink en H. Venema (2000). Beheer kwelderwerken. Verslag monitoring waddenkust Friesland en Groningen nov. 1999- nov. 2000. Alterra en Rijkswaterstaat directie Noord-Nederland, 19 pp. + bijlagen.
