After 400 years, Wallasea's sea wall comes tumbling down to create giant wetland site

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After centuries of trying to keep the sea out of East Anglia, the British Government yesterday let it back in. A fleet of bulldozers, excavators and dumper trucks made three breaches in the sea wall at Wallasea Island, Essex - which has been in place for at least 400 years - to create the UK's largest man-made marine wetland.

Last night, the sea was covering 115 hectares of former wheatfields, which from now on will be saltmarsh and mudflats on which migratory wildfowl and wading birds can find shelter.

It will also improve flood defences, provide for better fish nurseries, and create opportunities for recreation, said officials from the Department for Environment, Food and Rural Affairs (Defra).

The Government's £7.5m Wallasea Wetlands Creation Project is an example of "managed realignment" - coastal engineering to accommodate the sea-level rise that is being brought about by global warming.

Building higher and higher sea walls to check rises in the sea level will simply mean the inter-tidal zone, the area between high and low tides which is the crucial feeding ground for many wading birds, will eventually disappear. So, in various places along the east coast, the coastline is being brought inland, to let new inter-tidal zones form.

At Wallasea, near Burnham-on-Crouch, a new sea wall has been built behind the old one, and in the latter, three breaches totalling more than 300m in width were made yesterday to let the sea flood in to cover what was formerly farmland. The project will see the formation of 115 hectares of wetland, including seven artificial islands, saline lagoons, mudflats, new public footpaths, and four kilometres of sea wall.

The Government is creating the new habitat in compensation for similar wetlands that were lost in the Medway estuary in Kent when the Lappel Bank cargo terminal was built in the 1990s.

The Lappel Bank marshes were a protected area under the EU's birds directive, and after a challenge from the Royal Society for the Protection of Birds (RSPB) the European Court ruled the Government had acted illegally in letting them be developed.

Under the terms of the directive, the Government was obliged to provide habitat in compensation for that which had been destroyed. The RSPB has waited the best part of a decade to see the new habitat made. "We welcome it very much, and better late than never, but it is very late," said Mark Avery, the RSPB's conservation director.

The new saltmarshes and mudflats will be of particular importance for wintering wildfowl and wading birds, especially migrants that breed on the Siberian tundra then fly to Africa for the winter, stopping off in Essex en route, such as bar-tailed godwits, grey plovers, knots and dunlins.

"At Wallasea, we have balanced the needs of wildlife, flood management, landscape and people to recreate some of the ancient wetlands of East Anglia," said Barry Gardiner, the biodiversity minister, yesterday. "Saltmarsh is rarer than rainforest and is important to people, particularly as a flood and storm defence, and to wildlife. Hundreds of thousands of wetland birds rely entirely on the Essex saltmarsh for their food each winter.

"The wetlands will also provide additional flood and storm protection. Damaging storm waves lose their energy as they pass over the area, and the new sea defences will provide better protection than the old ones, which were in very poor condition," Mr Gardiner added.

Essex originally had 35,000 hectares of saltmarsh but enclosure for agriculture and development between the 16th and 19th centuries destroyed much of that habitat. Only 2,000 hectares remain.