Managing coastal environments
Managing coastal environments

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Managing coastal environments

2.2 Change and response in the ‘meadows of the sea’

Midway along the northern shore of the Blackwater estuary lie the Old Hall Marshes on a peninsula three and a half miles long and lying between tidal creeks and mudflats (see Figures 3 [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] and 15a). It is a wild, flat, remote area of mixed habitats of reedbed, open water, saltmarsh and improved and unimproved grassland. Ecologically, it constitutes coastal grazing marsh (Figure 15b) defined as ‘periodically inundated pasture or meadow with ditches which maintain the water level, containing standing brackish or fresh water’ (Essex Biodiversity Action Plan, 1999, p.145). These marshes, the so-called ‘meadows of the sea’, are vibrant with life. Old Hall Marshes contain 268 recorded plant species, among them the rare saltmarsh goosefoot (Chenopodium chenopodioides), sea barley (Hordeum marinum) and golden samphire (Inula crithmoides). There are over 24 mammals and about 1,000 species of invertebrates, and over 100 of them are rare. Fish and shellfish, including oysters, thrive in the creeks surrounding the marshes. Above all, these marshes provide breeding and feeding grounds for 240 species of birds, especially wildfowl (50 per cent of the total numbers in the Blackwater) like wigeon and teal, and waders (32 per cent) such as redshank, golden plover, dunlin and lapwing.

Figure 11
Figure 11 Four species seen in Old Hall marshes

Old Hall Marshes are a crossroads, a fulcrum of bird migrations that link the local ecosystems to habitats thousands of miles away. Some species use the marshes as a stopover on the long journey south along the Eastern Atlantic Flyway to Africa, while others spend the winter here. Particularly prominent are the dark-bellied brent geese that breed in the Taimyr Peninsula in the Arctic tundra of Siberia before wintering on the marshlands of the southern North Sea basin. Old Hall Marshes support a peak of approximately 4,500 of these birds in winter, about two per cent of the total world population. In order to conserve the value of these marshes for habitats and wildlife they have been designated as a National Nature Reserve and with the rest of the estuary are protected in a variety of other ways.

Click here to view: Protected environments: Old Hall Marshes provide rich habitats and feeding grounds for wildlife (map supplied by RSPB).

Figure 12
Figure 12 Grazing on the ‘meadows of the sea’.

Conservation has become an important element in responses to natural and social changes in these marshlands. Old Hall Marshes are relatively recent, converted from saltmarsh to grazing marsh in a succession of reclamations that started in the sixteenth century and that are marked by counter-walls across the area. The purpose of reclamation was commercial, providing land for pasture for both sheep and cattle. Though remote, the marshes were just a two-tide journey by sea on a sailing barge to and from the London markets, so encouraging a profitable trade in animals reared or fattened on the marshes for meat or wool.

Figure 13
Figure 13 Brent geese: (a) their migration route to the over-wintering site in the Blackwater, and (b) in flight over the estuary.

The marshlands had other human uses, too: there are still traces of the decoy ponds used to ensnare wildfowl for fresh meat, and from the nineteenth century the marshlands attracted wildfowlers shooting birds for sport. Indeed the fact that this land supported large numbers of birds was a key reason for the survival of Old Hall Marshes while grazing marshes elsewhere were being ploughed up in the drive for food production during and after the Second World War. Since 1984, Old Hall Marshes have belonged to the Royal Society for the Protection of Birds, thus ensuring the conservation of the site as grazing land (cattle in summer, sheep in winter), grazing being essential for maintaining certain habitats and species.

Figure 14
Figure 14 The decline in grazing marshes in Essex: (a) in the 1930s, and (b) in the 1980s. Source: RSPB.

Under the EU's Habitats Directive, coastal management must be sustainable; that is, there should be no net loss in terms of area of intertidal habitats. This poses a considerable challenge since in recent years both grazing marshes and saltmarshes along the Essex coast have declined considerably. Over two-thirds of grazing marsh was lost during the twentieth century, the biggest losses through conversion to arable land (Figure 14). But on the seaward side the protection of grazing marsh has contributed to the loss of saltmarsh. Since medieval times, enwalling has converted about 40,000 hectares of the Essex saltmarsh for agriculture leaving only 4,400 hectares, which is 10 per cent of the UK's total. This area has been eroding at the rate of two per cent per year (over one fifth of the total was lost during the last quarter of the twentieth century). The saltmarsh's gradual migration inland, as the sea level rises, is blocked by the sea wall, and the marsh is caught in a ‘coastal squeeze’ between the walls and the rising water. As Figure 15 shows, the gradual erosion causes a loss of important habitat as well as a reduction in an important form of coastal protection. With the onset of human-induced climate change the very survival of the coastal marshlands is at stake.

Figure 15
Figure 15 'Coastal squeeze’ occurs when saltmarsh is prevented from migrating inland away from the rising sea level (adapted from Environment Agency).

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