Ancient fen thrives on modern technology: A unique wetland is now a national nature reserve. Oliver Gillie reports

WICKEN FEN, a magical area of sedge moor and still pools, was yesterday declared to be a national nature reserve. Sometimes described as one of the last pieces of natural fenland in East Anglia, its naturalness is now preserved by highly artificial means. A plastic membrane 12ft deep surrounds much of it to conserve the water, which would otherwise leak into surrounding farmland.

Within this boundary a treasury of strange plants grow, including hornwort, a flowering plant that lives entirely submerged, and the insectivorous bladderwort which bears its flowers on shoots poking out of the water. The fen, acquired by the National Trust in 1899, is decorated by water lilies, bulrushes and yellow flag (iris) and is the home of 16 species of dragonfly, a variety of lizards, and the slowworm.

Wicken Fen has been shaped for centuries by man's activities in gathering peat for fuel, and sedge and reed for thatching. This created a diversity of environments in which wildlife flourished. However, cutting of sedge ceased around the turn of century and the area was invaded by scrub. Traditional human activities will continue at the reserve to conserve the environment as formed by man.

The installation of the plastic membrane has had a dramatic effect on the plant life. The water level in the fen has risen and sedge and other wetland plants are thriving. Two rare species of plant, the fen violet and the fen ragwort, are expected to flourish as a result of the rising water table.

Tim Bennett, warden of the Cambridgeshire reserve, said: 'The vegetation is growing so luxuriously this year that we have not been able to open some of the paths yet. It is very difficult to penetrate some areas because it is so thick. The wild parsley (a white umbelliferous plant resembling the wild carrot) is flourishing as never before. We are delighted because it is the food plant of the swallowtail butterfly, which we are going to reintroduce later this year as part of a species recovery programme.'

(Photograph omitted)