Almost 5,000 acres of land in East Anglian coast could be at risk from flooding because of coastal erosion, a report claims.
Land along the East Anglian coast is in danger of erosion by the sea
The National Trust says massive changes to the region's coastline are inevitable over the next few decades.
In a document called Shifting Shores, the trust is calling for action to cope with rising sea levels which will cause erosion and flooding.
A report says lengths of the coast in Norfolk, Suffolk and Essex are at risk.
It also claims improving sea defences is expensive and counter-productive because they create even greater problems for communities and the environment elsewhere.
Tony Burton, director of policy and strategy at the National Trust, said: "Over the next few decades extensive coastal change, especially flooding and erosion caused by sea level rise and more frequent storms, appears inevitable.
"The UK cannot ignore the issue and all sectors must plan how to adapt to a future of advancing seas."