One of the walks follows the intriguingly named Great Eastern Pingo Trail, on the edge of Thetford Forest in Norfolk. A pingo is an Eskimo term for a low conical hillock formed by water freezing beneath the surface and pushing the soil upwards. When England's pingos melted at the end of the last Ice Age they left a series of shallow craters, natural ponds which act as a magnet for wildlife. A small area of Norfolk around the Thompson Common Nature Reserve contains some 300 of these pingos.
The full circular trail is 8 miles long, but I settled on a shorter five- and-a-half mile version, one of the options on 12 October. From the car park in the yard of what was once Stow Bedon railway station the path leads past a notice-board and into the reserve. Soon I was looking at my first pingo, a small pool of water in the midst of what could have been primeval forest. How wrong I was. "These trees have only been here for around 50 years," said Bev Nichols, a warden with the Norfolk Wildlife Trust. "But the pond is 10,000 years old. That really freaks me out."
The Trust is busily trying to clear away some of the scrub so that the pingos can recover their natural grassland. Following waymarks to a clearing, we came to the largest pingo of all, deep in its crater surrounded by marshy plants - sedge and reed, water-mint and gypsywort. A year ago this was thick scrub, but already orchids and cowslips are starting to return. The pingos attract insects too - dragonflies, butterflies, mosquitoes. The emerald damselfly was thought to be extinct until it turned up again here. White admirals feed on the brambles in summer, and this week there were bright red ruddy darters (dragonflies) buzzing around the pond.
Look out carefully for the waymarks - several have recently been stolen, which makes navigating difficult. Don't miss the stile on the left, which leads into a small wood, from which you emerge to swing left onto a narrow road. Eventually this becomes a shady track, its hedges alive with autumn berries, with views over chalky grassland, grazed by Shetland ponies to one side and acres of farmland to the other. When the path narrows, a stile leads back into the reserve. As I walked beside a dry stream in Thompson Carr, a muntjac crossed my path and a pheasant furiously flapped its wings.
Keep following the waymarks, right onto a broad track, then left through oak woods and bracken to reach a small car park (complete with dried-up pingo) and a path to the artificial lake known as Thompson Water - a favoured spot for winter wildfowl. The main trail continues ahead, turning left when it reaches Peddars Way, an old Roman road, now a long-distance footpath.
Stern notices on your right remind you that this is an Army firing range, where war games are played most days. What effect does all that have on the wildlife? "Without it, this would be 17,000 acres of carrot fields. Without it, there wouldn't be otters and ospreys on the lake," said Ms Nichols.
The full 8-mile trail continues along Peddars Way, but for the short- cut turn left where you see the red-on-white Forestry Commission "89" marker. Go left again at the end of this forest track, then right on a country lane until you reach Crow's Farm. Here you can pick up the Pingo Trail again. Turn left onto a narrow footpath, where squirrels scuttle and birds sing, and try to imagine that just 50 years ago this was a busy railway line used by soldiers and schoolchildren. Keep going and eventually the path returns to the car park where the walk began.
l Distance: 51/2 miles. Time: 21/2 hours. Maps: OS Landranger 144 or Pathfinder 922. Stow Bedon is on the A 1075 Thetford to Watton road and the car park for the walk is situated behind a lay-by at the north end of the village. Dogs are not allowed into the Thompson Common Nature Reserve. On Sunday 12 October, there are options of 51/2 miles or 8 miles (without dogs) and 2 or 6 miles (with dogs), all starting from 10am.
l For details, ring 01953 884714. For details of walks elsewhere, ring the WWF Hotline on 01483 426269.