'Bog oaks' reveal ancient forest

Naturalists in Cambridgeshire say they have been astounded by the large number of ancient trees that have been found preserved in the peat soil of the Fens.

Conservationists say dozens of the "bog oaks" - which can be up to 40ft (12m) long - have been unearthed.

They say it is not unusual to encounter one or two during ploughing - but in some areas dozens have been found.

Conservationists say more may be discovered as the Fenland peat is drying out and oxidising.

Fascinating example

The remains of a forest that existed after the ice age, the trees rotted and fell into the peat soil, providing a snapshot of ancient natural history.

It is believed that the peat is disappearing at the rate of about an inch a year.

Although the trees are known by the local name of bog oaks, they can also be yew or pine.

BBC environment correspondent Sarah Mukherjee said they look as though they have just been felled - although some are blue or dark red from the minerals they have absorbed.

Chris Gerard, from the Great Fen Project, says they are a fascinating example of how the area has changed.

"When the glaciers retreated, at that time the sea level was quite low and the Fen basin was a very dry area, and covered in woodland," he added.

"With the rising sea levels, the rivers couldn't get out to the sea so quickly, they started to flood the Fen basin and that created the big Fen wetland, which the Fens is really known for, and all the trees that existed then died and fell into that emerging peat soil."

Paul Mason, from the Haddenham Conservation Society, said they were usually found in twos and threes at most.

"In my fifty years of experience of the Fens here I've never seen this many come up at any one time together," he added.