Saltmarsh, sand dunes, mud flats, wet grasslands and reedbeds, which support some of the country's most valuable plant and bird communities, will be physically recreated elsewhere, with Whitehall footing the bill, the minister responsible for flood defence, Elliot Morley, is to announce.
The pledge is a remarkable environmental commitment that may end up costing the Government enormous sums.
As Britain, and particularly south-east England, is affected over coming decades by the rise in sea levels induced by climate change, the areas threatened with destruction or disappearance under water will be extensive.
Seas rise as the warming water in them physically expands. Since the South-east is already facing a rise of about 25cm (10in) between now and 2040, the Government may find itself committed to recreating hundreds of thousands of acres of habitats.
But it considers itself obliged to conserve at all costs the several hundred wildlife sites that have been set up under European law. "These valuable habitats must be saved and the Government is committed to provide the funds to do this," Mr Morley said. The Ministry of Agriculture is today publishing a draft of the coastal habitat management plans that will be used to manage the sites at risk.
Its initial estimate is that there are 55 such sites in England and Wales, ranging from the Humber estuary and the Wash, around the south-east coast to Poole harbour, and then on the west from the Severn estuary to the Solway Firth.
However, Mr Morley's promise may not be enough to satisfy environmental groups, which are calling for a much more radical strategy to safeguard the whole shoreline from the rising tide.
The World Wide Fund for Nature and the Wildlife Trusts want the Government to embrace "managed retreat" - the policy of not trying to hold back the incoming sea but allowing it to flood on inland.
This is because rising seas, as they come up against concrete coastal defences, destroy the inter-tidal zone - the area of mud between high and low tides that provides enormous numbers of worms and small crustaceans as food for fish and birds.
These areas, ecological studies have shown, have a greater biological productivity than tropical rainforest and are vital for coastal wildlife.
Environmentalists say the way to protect them is - paradoxically - to do away with much of the 1,500 miles of solid concrete defences that at present hold back the sea.
If the sea is allowed to flood in to coastal land, new inter-tidal zones will form.
The inter-tidal zone itself, with its mud and then its plant-covered saltmarsh, acts as a natural sea defence mechanism.
"A vicious cycle of destruction has been started," said Paul Murby of the Wildlife Trusts. "As the sea defences get bigger and more expensive, more inter-tidal habitat is lost, leading to the need for even bigger and more expensive defences. The cycle has to be broken."
A report sponsored by the trusts and the WWF, published today, claims that in parts of England it is simply not economic to hold back the sea with concrete sea walls - the value of the land saved is less than the cost of building the defences. The implication is that it would be cheaper to pay farmers to abandon their land in the face of the sea than build defences to protect it - and environmentally sounder.