Walney Island is only 5m (16ft) high and about 300m (980ft) wide at its southern end, where it is most vulnerable to intrusion by the sea.
The seaward edge of the island is being eroded by about 1m every year so the island's inhabitants fear that it might easily be breached one day by an adverse combination of heavy weather and a strong tide.
The future of the island is now being considered by a Department of the Environment inspector following a six-week inquiry. A local farmer, Michael Mulgrew, wants to dump waste on the island to raise its level and so make it less likely to be breached by exceptional seas.
His plan is supported by the port authority for Barrow and the local authority, Cumbria County Council, but is opposed by English Nature and environmental pressure groups such as the Cumbria Wildlife Trust.
John Hetherington, environmental planning officer with Cumbria County Council, said: 'The consequence of a breach of the island would be disastrous for Barrow. But the chances of a breach are very small indeed and if one occurred expert evidence suggests that it could be quickly filled in.'
The island boasts a nature reserve and is home to thousands of seabirds, which feed on the extensive mudbanks and flats of Morecambe Bay. At extreme low water about 310sq km (120sq ml) of the bay are exposed, the largest single area in Britain under tidal cover. The bay is recognised as a wetland of international importance.
Many thousands of terns and gulls, and 12 species of waterfowl, including three species of plover, pink-footed geese, pintail, curlew and redshank, thrive on the marine life on these mudflats and come back to Walney Island and other parts of the shore to roost as the tide rises.
Some of the scarcer species sought by bird watchers can be found here: the great crested grebe, wigeon, eider duck, merganser, sanderling and the black- tailed godwit.
Paul Kirkland, of the Cumbria Wildlife Trust, said: 'Interference with the natural coastal processes which cause the shingle to move along the island and build up into shallow banks at the south end in the Piel estuary would affect the bird populations directly.'
The original plan for strengthening the sea defences of the island involved using money charged for waste dumping to build up buttresses called skears along the seaward side of the island. Like groynes, these dissipate the energy of waves and cause some of the suspended shingle and sand to be deposited.
But a new philosophy of sustainability now informs decisions on coastal defence. This proposes that receding coastlines should not be defended by hard engineering structures but rather by a strategy of 'managed retreat'.
A rubbish dump might pay for some concrete skears but they might increase erosion elsewhere, and in any case would eventually be washed away.
Better, some believe, to let the land be flooded, let the coast erode and the shingle be heaved around by the waves. The seawall may be breached but like a living thing it should heal itself. 'It means leaving the future of the island to unfettered natural processes and we are not sure if we dare do that,' Mr Hetherington said.
'It means trading off an individual's right to prevent his land from flooding and perhaps being washed away against the value of leaving natural processes to themselves, and allowing our coasts to be maintained without expensive intervention.'
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