Redgrave and Lopham Fen in Suffolk, the peaty, marshy source of the River Waveney, has been gradually drying out for the past 30 years and is turning into a scrubby, unremarkable woodland as a result.
Many of the 120 rare invertebrates which live there, including the floating fen raft spider and a type of fly that eats snails, are under threat. The fen is also used by some rare birds and mammals, including the otter.
Its problems began when a water company borehole was sunk about 100 yards from its edge in the late Fifties. That lowered the water table and reduced the upwelling of water from chalky rocks which feeds the fen and river.
Next, the river itself was deep-dredged, better to drain the farmland it flows through on the Norfolk-Suffolk border. That speeded the rate at which water flowed out of the fen, accelerating the drying. Further more, traditional uses of the fen for grazing livestock and mowing sedges declined, allowing scrub to invade.
One of the jewels in Britain's wildlife conservation crown, a 325-acre National Nature Reserve, was fast losing its worth. Inland wetlands fed by chalk springs are a rarity across Europe.
Now two government organisations, the National Rivers Authority and English Nature, have combined with the Essex and Suffolk Water Company - which owns the borehole - and the voluntary Suffolk Wildlife Trust to implement the rescue plan.
Nearly half of the pounds 3.2m cost is being met by European Union funding, because the project is seen as a demonstration of collaboration between competing interests to preserve an important habitat.
The most expensive part of the project is the closure of the borehole and the drilling of a new one, some distance away. That should happen by the end of 1997. The water depth in the river will also be increased and the flow slowed by using sluices, to be installed next year.
This summer an excavator began work stripping out the top layer of dried- out peat which now covers much of the fen surface, exposing the pristine peat below.
The desiccated top layer has become too fertile for the type of plants which characterise the fen, because locked-away nutrients are released during the drying out.
The willow and birch invaders are being felled with chainsaws, and sheep and cattle are being brought in to graze the fen once more.
''We'd reached the point where this really was the last chance for this very special habitat,'' Mike Harding, reserves manager with the Suffolk Wildlife Trust, said.Reuse content