Enclosure of saltmarsh

The most common and extensive form of saltmarsh loss is enclosure, usually associated with agricultural activity. There are numerous examples of agricultural land which have been "won" from the sea in this way. Estimates of losses from some of the major estuaries total in excess of 91,000ha (Davidson et al. 1991). For example new agricultural land was created in the Wash, 29,000ha including 3,000 in the 20th Century (Dalby 1957) and in the Ribble Estuary (see Figure below). Because enclosure only takes place when the saltmarsh is 'ripe for reclamation' sea walls built to exclude the tide are normally positioned at the upper, most diverse section of the marsh. Thus the combined effect of this is to destroy the area of marsh enclosed, together with its associated fauna and to truncate the sequence of habitat for other animals which use the upper marsh for part or all of their life cycle. The enclosures have usually been progressive and cumulative.

Caption: Saltmarsh enclosure for agricultural use on the Ribble Estuary, Merseyside (after Doody 2001)

References

Dalby, R. 1957. Problems in land reclamation: 5 Saltmarshes in the Wash. Agricultural Review, 2., 31-37.

Davidson, N.C., Laffoley, D..d'A., Doody, J.P., Way, L.S. & Gordon, J. 1991. Nature Conservation and Estuaries in Great Britain. Nature Conservancy Council.

Doody, J.P. 2001. Coastal Conservation and Management: an Ecological Perspective. Kluwer, Academic Publishers, Boston, USA, 306 pp. Conservation Biology Series, 13