Invaders make way for return of the fens: Norfolk's ancient landscape of water and reeds is being recreated by clearing the trees and scrub that took over the habitats

THERE ARE places where you can walk on water in the Norfolk Broads. A floating raft of mud and reedy vegetation known locally as 'hover' can support the weight of an adult, although it wobbles and surges underfoot like a giant waterbed.

The Broads Authority and English Nature, the Government's conservation arm, are trying to recreate hover and other vanishing habitats by digging new, small Broads in the underlying peat. They use their own mechanical excavator which, seen roaring away in a remote, verdant fen, makes a strange sight.

Local people were still digging peat until the end of the last century. Areas of common land were set aside by the parish for the poor to dig out their fuel. These shallow pits would fill with water, reeds would crowd in and, after about 100 years, a layer of hover would build up which might eventually solidify into boggy fen.

Centuries of peat digging meant that the area was always in transition, with unusual plants, birds and insects in a succession of habitats - open water, hover and fen. Hover is home for the fen orchid and the crested buckler fern.

Then the peat digging stopped and the watery, reedy landscape which had existed for centuries began to disappear. The lakes have been so over- fertilised by human sewage flowing down the rivers that only algae and a few small fish can survive. Most of the marshland bordering the lakes and rivers which used to flood regularly has been drained for pasture and crops.

The land that survived undrained was rapidly invaded by trees and scrub because the reeds, sedges and other plants were no longer cut to provide roofing, hay and animal bedding.

With the demise of traditional land uses, the heart of the Broads was in danger of becoming one large, boggy wood with stagnant lakes. It might make a nice view from a cabin cruiser, but in the context of conservation it is drab and degraded.

The Broads Authority and its partners are trying to stop the rot by simulating the bygone rural economy. An 18-ton second-hand mechanical excavator is not the same as dozens of peat diggers, but it is the cheapest, most effective way of getting the job done. Three new ponds have already been created and the Broads Authority plans to dig more right across the Broads.

The machine, owned jointly with English Nature, clears away scrub and trees while scooping out a pit. The depression quickly fills with clean groundwater, clear of sewage and able to support once-abundant aquatic plants, such as the stonewort.

At first, these pits look ugly; large black scars in the greenery. But within a year their banks will be covered in vegetation, reeds fringe the edge and dragonflies are darting everywhere.

Jane Madgwick, the Broads Authority's chief conservation officer, pilots an oblong, flat-bottomed work boat, known as a baking tray, through half a mile of narrow dyke off the River Ant which leads to the first pond, dug 13 months ago. 'It looks brilliant,' she says proudly.

She hopes the new ponds will encourage the return of one of Britain's rarest birds, the bittern. It needs thick reed cover and clear water in which to hunt for fish. 'If there's one species we'd love to get back, it's that one,' she says. Only two pairs bred in the Broads this summer.

(Photographs omitted)