Government plans to breathe new life into the Grevelingenmeer lake in Zeeland threaten to swamp islands and mudflats used by thousands of birds, nature organisations say.

Last year, the cabinet decided to put €75m into opening up the Grevelingenmeer to the sea again, bringing new life into what has been described as an ‘underwater cemetery’.

The lake was completely closed off from the North Sea in the 1970s as part of the Delta works flood prevention scheme. But this effectively starved the ecosystem of oxygen.

The project, which is scheduled to be completed by 2024, involves partly breaking through the Brouwers dam to bring back tidal movement to the Grevelingenmeer, so feeding oxygen into the water.

Officials hope that populations of crabs, lobsters, oysters and shrimp will again flourish, as will underwater vegetation.

However, the Worldwide Fund for Nature, bird protection lobby group Vogelbescherming and other green groups are now warning that the plan, which will raise the level of water by half a metre, will lead to the islands and the mudflats being either covered or washed away.

‘We are in danger of throwing the baby out with the bathwater,’ WWF spokesman Bas Roels told the AD. ‘Nature which has been protected will drown… We have to protect the nature behind the dam so that we don’t regret this move later.’

‘In the short term, it will be necessary to raise the islands and shoreline,’ he said. ‘Hopefully, in the long term it will be possible to let the land grow with sediment from the sea.’