Plans to expand an area of Fenland in Cambridgeshire have been defended after claims the development would destroy ancient waterways.
The National Trust aims to protect wildlife with the fen expansion
The Wicken Fen Vison Project will see the National Trust expand its reserve by 42 hectares as part of plans to enhance the habitat.
The Don't Ditch our Lodes Campaign group said expansion could destroy the Cambridgeshire lode drainage tunnels.
However, the trust said it aims to protect and maintain lodes in the area.
The project is a 100-year plan to recreate a traditional wetland landscape stretching from Wicken to the edge of Cambridge.
It involves creating floodplains grazing marsh, wet woodland, fen and reed bed to benefit wildlife including otter, water vole, bittern, song thrush and great crested newt.
Campaigners have said that if the lodes are removed the project could lead to the loss of agriculture.
Geoffrey Wollard, of Don't Ditch our Lodes Campaign, told BBC News: "They're wasteful because they could mean the loss of 10,000 acres of good agricultural food producing land.
"But worst of the lot, they're counter conservationists because their plans could mean the undermining of the lodes from the outside. "
The trust denies the plans would undermine the banks which support the lodes.
Jon Megginson, of the National Trust, said: "I think categorically, I can say that the lodes are such an essential feature - in fact protecting them, ensuring that they are maintained, is very much part of our vision."