Key species • British saltmarsh types • Spartina marsh

Spartina marsh

An important change in British (and many other temperate-zone) saltmarshes during the last century was caused by the evolution, spread and subsequent partial decline of the English cord grass Spartina anglica. The spread of the grass from its site of origin (Southampton Water), at first naturally along the south coast as far as Poole Harbour in the west and Rye in the east, but later by deliberate introductions all around the coast, is well documented. The main reason for planting was to improve the rate of colonisation and stabilise mudflats, either as a precursor to land claim for agriculture or for coastal protection.

In the late 1980s, Spartina dominated 6,950ha of tidal flats, 16% of the British saltmarsh habitat and 2% of the estuarine intertidal zone (Way, 1990). More recently, Gray et al. (1997) suggested that there were more than 10,000ha of Spartina in the 44,000ha of saltmarsh around the British coast. Nearly all of which was thought to be the fertile polyploid, although small pockets of the sterile hybrid do occur, notably on the south coast. Gray et al. (1997) also report that Spartina grass continues to spread on the west coast, with around 20 new sites and a 40% increase in area since 1965. However, on the east and south coasts the Spartina marshes have reduced in area since then, by around 44% and 11% respectively (Gray et al., 1997).

This regression of Spartina marsh ('die-back') was first noticed in the 1920s in the longer-established swards of south coast estuaries. The conditions under which it degenerated were characteristically badly drained, highly anaerobic soils with a high proportion of fine particles and high sulphide content. That is, by causing the rapid accretion of poorly drained sediment and often creating marshes with a concave profile, the Spartina itself was the cause of the deterioration. It has also been shown that a fungus (Claviceps purpurea) can contribute to die-back by significantly reducing seed production through the infection of embryonic tissues (Gray et al., 1991).

The invasion of Spartina on the northern and western coasts of England , where it has encroached onto amenity beaches (e.g. at Southport ), colonised mudflats that are bird-feeding areas (e.g. at Lindisfarne ) or threatened the floristic diversity of nearby saltmarsh (e.g. at Alnmouth), has prompted attempts to control further spread using a variety of physical and chemical methods. However, in other areas Spartina marsh is being encouraged, protected or even planted, in an attempt to limit the loss of saltmarsh. Appropriate management of this key species is likely to require consideration of the entire local saltmarsh and mudflat system, including the sediment supply.