The National Trust has sunk three decommissioned barges in the Blackwater Estuary, Essex, to form a new island habitat for birds.
Up to 8,000 cubic metres of sediment – the volume of three Olympic swimming pools – will be used to fill and surround the vessels, requiring around 170 dredge barge trips from Maldon harbour.
The sunken craft are former Thames lighters, dating from the 1950s, which once transported building materials, coal, and food from the Port of London.
The flat-bottomed barges measure between 20 and 32 metres long.
Holes have been cut in their hulls to sink them and use them as a stable structure that will become a habitat for birds.
These include dunlin, curlew, lapwing and ringed plover, as well as vulnerable seabirds such as little terns and avocets.
Katy Gilchrist, coastal project manager for the National Trust, said: “This is the ultimate act of marine recycling —transforming retired industrial vessels into a sanctuary for wildlife.
“We’re basically turning history into habitat and, as far as we know, no one has attempted anything quite like this before.
“The lighters have been decommissioned for some time, so work was needed by specialist contractors to make them clean and seaworthy again before they could be towed into place and set on to a platform of sediment.
“Holes were cut into the hulls to sink the vessels and they were then filled with sediment, mostly mud, to weigh them down to secure them.
“Once the island is fully established with gravel on top, it will sit safely above the highest tides to offer a safe refuge for some of our bird species which are in decline.”
Once the work is complete, the island will add 0.55 hectares (1.4 acres) of new habitat – almost the size of a football pitch – within the Blackwater Estuary.
The new island is being built just off the eastern shore of the National Trust’s existing Northey Island.
Matt Wilson, countryside manager for the National Trust, said the island “will provide a refuge for birds above the highest tides and away from disturbance on shore”.
“Depending on the time of year, the different birds we hope to see include oystercatchers, Brent geese, redshank and curlew,” he said.
“We will be continuing to top the island with sediment for a little while and then we’ll just have to wait to see when the birds will start to use their new sanctuary.
“As well as creating a new habitat for birds, the island will also help to reduce erosion of the existing saltmarsh at Northey Island.
“As the tide comes into the estuary, the force of the water erodes the saltmarsh which acts as a natural flood defence, massively impacting the wildlife that depends on it.
“Saltmarsh is one of the biggest natural carbon stores in our marine landscape.
“By sheltering the marsh from wave energy, the new island will also help us slow erosion and protect this precious, habitat.”
