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Grazing management on saltmarshes
Grazing pressure has a profound effect on the nature of the biological
value of an individual saltmarsh. This is particularly true for the
more mature plant communities which are inundated relatively infrequently. The
biggest contrast in values lies between lightly grazed saltmarshes where plant
diversity, invertebrates and breeding birds are all favoured. At the other extreme
high stocking densities result in close-cropped swards which have the greatest
value for wintering (especially grazing) ducks and geese.
| Grazing regime |
Grazing by |
Comment |
| Traditionally ungrazed or lightly grazed |
Native herbivores (ducks and geese, hares and rabbits) and/or low level,
intermittent grazing by domestic stock. 2 - 3 sheep or 0.7 - 1.0 young
cattle per ha, or lower, for 6 months of the year, April and October (Beeftink
1977).
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Probably closest to 'natural' marshes which have a complete
sequence of vegetation from pioneer to strandline and transitions to terrestrial
habitats. There is good structural diversity, plant communities with grazing
sensitive species, a wide range of invertebrate animals and breeding birds. |
| Moderately grazed |
Domestic Stock (5 - 6 sheep or 1.0 - 1.5 young cattle per
ha between April and October), typical value. |
Intermediate conservation value which is to some extent dependent
on the type of animal. Cattle tend to produce a structurally more diverse
vegetation than sheep. |
| Heavily grazed |
Grazing levels equivalent to 9 - 10 sheep or 2 - 2.5 young
cattle per ha. (April - October) approach those of inland grassland. In
northwest England where some of the most extensive and intensively grazed
sites occur, stock densities up to 6.5 sheep (year round) plus 2 cows (Summer)
per ha. can occur (Gray 1972). |
These stock densities are those used for agricultural requirements.
Generally botanical (and invertebrate) biodiversity is low. [Note on some
high level marshes, including those fringing the sea lochs of Scotland,
the flora may be visually distinct and include northern species such as
Blysmus rufus and a rich variety of small
free living fucoids (Adam 1990).] At
these levels breeding birds are affected by nest trampling. |
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General guidance: The above figures are indicative only. Setting
grazing levels for a particular marsh is difficult. Prevailing weather
conditions, previous stocking rates and other environmental considerations
must all be taken into account. Do animals, for example, have access to
the marsh all year round and at all stages of the tide? Is there a link
between grazing on the saltmarsh and adjacent farmland, such that the
marsh is used only infrequently? When deciding on an appropriate grazing
regime the existing interests and history of management are important
considerations.
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References
Adam, P.
1990.
Saltmarsh Ecology. Cambridge University Press, Cambridge, 461 pp.
Cambridge Studies in Ecology
Beeftink, W.G.
1977.
Salt-marshes.
In: The Coastline, ed.Barnes, R.S.K.John Wiley & Sons, Chichester, 93-122.
Gray, A.J.
1972.
The ecology of Morecambe Bay. V. The saltmarshes of Morecambe Bay.
Journal of Applied Ecology, 9., 207-220.
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