Underwater surveys have shown that the rate of erosion on the island's eastern shore has accelerated to one metre per year, leaving a jetty, quay and islanders' cottages in immediate danger.
The National Trust, which has owned the nature reserve on the island off Poole, in Dorset, since 1961, is proposing to build underwater rock armour, consisting of 10,000 tons of boulders, to protect the seabed from the tide. "Brownsea Island fits so tightly into Poole harbour that it is like a cork in a bottle," said a spokeswoman for the trust's Wessex region. "The tide rushes past and into Poole harbour causing a scouring action that is wearing it away."
The National Trust has begun an urgent fund-raising appeal because they fear the quay, along with its gatehouse and eight cottages, may not survive another harsh winter.
Engineers say the island, which attracts 10,000 visitors a year, has a weak clay and sand shore which is being washed away by each wave. "Frankly we only need another force 10 gale and anything could happen," said Barry Guest, who manages the island.
Work to shore up the 146-year-old sea wall has begun. The estimated cost of the rock armour is pounds 250,000, some of which the trust will find from emergency funds. Each 1-to-2 ton boulder will cost pounds 30 and pounds 22,000 is needed to transport them out to sea.
The acceleration of erosion has probably been caused by a number of factors. Global warming, increased easterly winds and the deepening of Poole harbour to accommodate larger cross-channel ferries may all have played a role. The depletion of reed beds, where the native spartina has all but disappeared because of pollution, may also be a factor as the plant used to protect the sea bed.
Lord Baden-Powell founded the Scout movement on the wooded 500-acre retreat in 1907. He invited 22 boys from across England to take part in an experimental 10-day expedition to the island which still plays host to Scout groups.Reuse content