Grazing • Access and amenity • Pollution • Coastal defence maintenance • Alternative uses

Grazing (cont)

Light grazing • Moderate grazing • Heavy grazing • Abandoned grazing

Heavy grazing

Saltmarshes that have a history of heavy grazing by domestic stock tend to lack the attributes typical of the best examples of saltmarsh habitat, i.e. rich and varied plant and animal populations and a varied vegetation structure. Recorded grazing levels equivalent to 9 to 10 sheep or 2 to 2.5 young cattle per ha (April to October) approach those of permanent pasture. In northwest England, where some of the most extensive and intensively grazed sites occur, stocking densities up to 6.5 sheep (year round) or 2 cows (summer) per ha occur (Gray, 1972). At these levels, except at the very upper limits of unenclosed marsh, such as in Morecambe Bay, there is an impoverished flora.

As most, if not all, of the standing crop is removed by grazing in these circumstances, the structural diversity of the marsh is reduced. Consequently, the diversity of invertebrate species associated with taller vegetation decreases as grazing pressures increase. Furthermore, heavy grazing, whilst not necessarily removing the plants upon which the invertebrates are dependant, may reduce the physical structure of the flowers, fruits, seeds so that many species may become excluded (Meyer et al., 1995).

At the same time, grazing sensitive species are eliminated and tillering grasses favoured. Over time, a close-cropped sward is produced which is typified by the " bowling green" lawns of northwest England and this is sometimes exploited for turf-cutting. These saltmarshes lack most of the attributes of the more moderately grazed sites but may (in some circumstances) have considerable importance for wintering ducks and geese. A few species, such as Oystercatcher, which breed in more open locations, can be found associated with these heavily grazed sites.