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Saltmarsh loss - southeast England
The loss of saltmarshes in southeast England has been the subject of a considerable
amount of research. Losses due to enclosure and subsequent use for agriculture
(including coastal
grazing marsh) amounted to some 4,340ha according to studies undertaken
to assess the implication of building a third London airport at Maplin Sands
(Boorman & Ranwell 1977). Visual evidence
also suggested that the saltmarshes remaining outside the sea walls were also
eroding. In order to establish the extent of the losses detailed surveys were
undertaken. The results are summarised below:
Table Caption - Loss of saltmarsh in the estuaries
of Essex & Kent 1973-1988 (Burd 1992)
| Estuary |
Original area (ha)
|
Total area lost (ha)
|
Loss (ha) to reclamation
|
Loss (ha) to erosion
|
% original area eroded
|
| Orwell |
99.5
|
39.9
|
7.5
|
32.5
|
32.6
|
| Stour |
265.2
|
129.5
|
13.3
|
116.2
|
55.0
|
| Hamford Water |
876.1
|
170.6
|
1.2
|
169.5
|
19.3
|
| Colne |
791.5
|
97.7
|
5.2
|
92.5
|
11.7
|
| Blackwater |
880.2
|
200.2
|
-
|
200.2
|
22.7
|
| Dengie |
573.8
|
56.7
|
-
|
56.7
|
9.9
|
| Crouch |
567.1
|
156.1
|
22.1
|
125.0
|
26.5
|
| Thames (Essex) |
365.9
|
105.6
|
22.3
|
83.3
|
22.8
|
| Thames (Kent) |
77.8
|
17.5
|
3.2
|
15.3
|
18.5
|
| Medway |
853.8
|
198.3
|
18.2
|
180.1
|
21.3
|
Swale
|
377.0
|
61.6
|
3.5
|
58.2
|
15.5
|
A further study related to Dengie (Essex) suggest annual losses of between
0.75% and 1.4% from 1960 and 1981 (Harmsworth &
Long 1986). A similar study from Suffolk between 1971, 1986 and 1998
revealed losses as follows (Coastal Geomorphological
Partnership 2000).
| Site |
Total saltmarsh area (ha)
|
Net change (ha & %)
|
|
Dates
|
1971
|
1986
|
1998
|
1971-1998
|
| River Blyth |
68
|
66
|
63
|
5ha (7%) loss
|
| River Ald/Ore |
265
|
267
|
257
|
8ha (3%) loss
|
| River Butley |
96
|
89
|
87
|
9ha (10%) loss
|
| River Deben |
312
|
266
|
241
|
71ha (23%)loss
|
References
Boorman, L.A. & Ranwell, D.S.
1977.
Ecology of Maplin Sands and the Coastal Zones of Suffolk, Essex and North Kent.
Institute of Terrestrial Ecology, Colney, Norwich.
Burd, F.
1992.
Erosion and Vegetation Change on the Saltmarshes of Essex and North Kent between 1973 and 1988.
Research & survey in nature conservation, 42
Nature Conservancy Council, Peterborough.
Coastal Geomorphological Partnership
2000.
Saltmarsh Change within the Suffolk Estuaries Between 1971, 1986 and 1998 - Executive Summary.
Environment Agency, Anglian Region, Eastern Area.
Harmsworth, G.C. & Long, S.P.
1986.
An assessment of saltmarsh erosion in Essex, England, with reference to the Dengie Peninsula.
Biological Conservation, 35., 377-387.
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