Coastal wetlands

Europe's largest coastal wetlands lie along the southern coast of the North Sea from Holland and North Germany through to the west coast of Denmark. The Wadden Sea, and its coastal marshes, are enriched by the effluent from the great rivers that cross the North German Plain, the Ems, the Weser, and the Elb. The highly productive marshes have a 7500-year record of human settlement which over the years has adapted to the considerable risks involved in harvesting the outstanding productivity of the salt marshes and swamps. The earliest Neolithic communities in the Wadden Sea region were confined to summer camps. Gradually, Neolithic and Bronze Age settlers learned to make increased use of the fertile salt marshes for pasturage through a form of transhumance with grazing on the marshes in summer and retreating with their cattle to higher ground in winter (Knottnerus, 2005).

While the Neolithic settlers used the wetlands as they found them, the Bronze Age farmers began to modify their immediate surroundings. Gradually, instead of limiting habitation to areas just above high-tide level, the inhabitants began to raise mounds (Wurten; Fig. 11.20) from sods and dung on which they

Fig. 11.20 Farm buildings on raised mounds (Wurten) which are typical of an early pattern of agricultural settlement in the low marsh region of East Friesland. (Photo Dr Felix Bittmann, Niedersaechsisches Institut fur historische Kuestenforschung.)
Fig. 11.21 Early cereals. (left) Bere barley (Hordeum vulgare var. tetrastichon and (right) black oats (Avena strigosa).

situated their farms and infields. In summer they would take hay and graze their animals on the marshes where they also cultivated salt-resistant summer crops, such as field beans (Vicia faba var. minor), the four-rowed bere barley (Hordeum vulgare var. tetrastichon; Fig. 11.21, left panel) and oats (Avena sativa). With the arrival of the winter rains they would then retreat to their mounds along with their cattle and sheep, followed by rodents, hedgehogs, weasels and stoats. By Roman times the riverbanks were densely populated and salt-making was actively pursued. From time to time there were periods of maritime regression and sites were abandoned as a result of flooding and storm surges. Particularly during the period AD 450-600 tribal wars and malaria drastically reduced the population and new settlers then migrated into the area from the east.

From the ninth and tenth centuries onwards drainage and dyking began to transform the landscape with the former salt marshes being protected by sea walls and eventually the incorporation of sluices for retaining fresh water and repelling floods. Crops that would thrive on the peat soils that had now developed on the marshes included rye (Secale cereale), black oats (Avena strigosa; Fig. 11.21, right panel) and buckwheat (Fagopyrum esculentum). This was partly interrupted in the fourteenth and fifteenth centuries by large-scale inundations of marshland. However, the progressive construction of embankments and sea walls (AD 1500-1800) did succeed in transforming much of the amphibic transition zone into arable land and freshwater lakes. In unreclaimed areas the nutrient-rich coastal ecosystem with its highly productive salt marshes continue to provide summer pasturage and hay meadows that support extensive grazing for both cattle and sheep. The drainage and dyking has also caused new plant communities to develop, and wet pastures with Molinia caerulea and waterlogged Glyceria meadows now extend the range of grazing lands.

Exploiting these areas has always required considerable effort as the nature of the terrain prevented the use of horses and carts. The rewards for this labour were considerable, and much use was made of rafts and barges to transport cattle to the pastures and harvest the herb-rich hay.

As with many estuaries and deltas throughout the world in recent times, dredging to provide shipping canals has caused the natural vegetation at the land-sea interface to lose its ability to retain and filter river sediments. Riverine loads are now flushed directly into the North Sea. This is also the case with the Mississippi delta where the loss of sediment that would have been spread over adjoining marshland and by transfer to deep water in the Gulf of Mexico has led to coastal habitat degradation and a decline in natural habitat diversity, falling shorelines, and increased risks of flooding (Reise, 2005). Rising sea levels are therefore likely to bring about substantial habitat reconfiguration on these sedimentary coasts where the marshlands have been starved of the sediment that might have enabled them to rise along with the sea level.

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