Land claim

Human reclamation of saltmarsh (i.e. land claim) for agricultural purposes began in several areas in Roman times, but was undertaken extensively from the later Middle Ages onwards (Allen, 1992; 2000b). In eastern and southern England, large-scale reclamation occurred along the margins of most estuaries and areas of marsh-fringed open coast between the 16th and 18th centuries (Gramolt, 1960) and further reclamation was undertaken in the 19th and 20th centuries. There are numerous examples of agricultural land that has been won in this way around e.g. The Wash, Ribble Estuary, the Essex and Kent coasts, the Severn Estuary and elsewhere. Estimates of losses from some of the major estuaries total in excess of 91,000ha (Davidson et. al., 1991).

Areas such as The Wash, and southeast England generally, also demonstrate more complex patterns of reclamation where, during the 19th and 20th centuries, some areas of reclaimed marsh were abandoned to the sea as economic conditions deteriorated and the maintenance of sea walls was scaled down or ceased. Following breaching and abandonment of sea defences, new saltmarshes became established on those parts of the re-flooded land that were high enough in the tidal frame to allow plant colonization, while mudflats developed elsewhere. New creek systems became established, initially influenced strongly by the patterns of agricultural 'grip and drain' structures but increasingly, over time, re-establishing a more natural pattern in equilibrium with hydraulic conditions (Crooks and Pye, 2000). In the Severn Estuary, this has had significant implications for morphology and sedimentation both on the reactivated marshes and adjoining areas (Allen, 2000b).

Following enclosure, saltmarshes were often used for grazing domestic stock. This traditional use of the land, without ploughing or agrochemicals, helped to create new habitats of wildlife interest; ‘grazing marsh’. When unimproved permanent pasture is used for low intensity grazing, it often develops a vegetation structure attractive to nesting birds. In winter, surface flooding of parts of these same areas attract wintering wildfowl such as teal, wigeon and waders. The presence of short grassland also provides grazing for waterfowl, including brent-goose. Furthermore, rare species of plants are often found in association with pasture and the brackish water drainage ditches, the latter being particularly important for a number of rare invertebrates.

More recently, these semi-natural habitats have themselves been claimed for intensive agriculture. This process has resulted in the loss of nearly 70% of the grazing marshes (and the associated loss of important plant and animal communities) in the Thames estuary since the 1940s (Thornton & Kite, 1990). This loss not only destroys the grassland (see figure below), but also results in degradation of those ditches which remain through eutrophication and pollution as a result of the use of modern chemical fertilisers and pesticides.

Development of coastal grazing marsh by enclosure of saltmarsh and its subsequent loss to intensive agriculture (from Toft et al., 1995)