Under the EU habitats directive, new artificial salt marsh must be created every time natural salt marsh is lost to coastal development or erosion caused by sea-level rise. New marshes must display “equivalent biological characteristics” to their natural counterparts. Apparently this is not always the case.
Man-made salt marshes in south England have been created by relocating sea walls inland and breaching the old, outer walls to let the sea to flood in, creating a marsh. Many accidentally created salt marshes have formed when old sea walls collapsed and let in the sea.
While salt-tolerant (halophytic) flowering plants colonised artificially created salt marsh rapidly, the composition of these marshes was “significantly different” to natural marshes.
Sediment conditions in lower-lying areas were less oxygenated than those at the same elevation in natural marshes, the study said, and man-made marshes tended to be drier. The artificial sites tended to be flat and featureless with scrappy vegetation and patches of bare ground.
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