Norfolk 'ghost pingo' project restores life to Ice Age ponds

Pingos are shallow ponds formed in post-glacial depressions which harbour a unique wealth of wildlife - but over the centuries many were lost after fields were filled in for agricultural use.

The Norfolk Wildlife Trust (NWT) reserve at Thompson Common, between Watton and Thetford, has around 400 pingos, but hundreds more are believed to be buried on the surrounding land.

Since purchasing the neighbouring Watering Farm in 2017, NWT has been working with experts including the Norfolk Ponds Project, University College London and the Norfolk Geodiversity Partnership to identify and excavate these ghost pingos.

Aerial images and LiDAR surveys are used to map possible locations, before core samples are drilled to find the layer of black peat which indicates the original base of a pingo - containing dormant seeds, potentially hundreds of years old, with the power to regenerate the pond's wildlife.

A 'ghost pingo' being excavated at Watering Farm near NWT Thompson Common (Image: Denise Bradley)

One of the 11 ponds to have been excavated at the site so far has been hailed as "the most species-rich pond I have ever seen" by a leading conservationist.

Prof Carl Sayer of University College London is also a director of the Norfolk Ponds Project.

"Of the thousands of ponds I have looked at in the last 20 years, this is the one with the most species, and it was only restored two years ago," he said.

"We have not introduced any plants, all we have done is scraped the infill out and exposed the seed bank layer, and let nature do the rest.

"Because of this incredible seed bank, with all these species preserved in it, I have recorded well over 40 wetland plant species, and several national rarities. Thompson Common is an amazing nature reserve, but there are species in here, on a former pig farm, that are not even present at Thompson Common."

Stonewort pond plants found in a restored 'ghost pingo' at Watering Farm (Image: Denise Bradley)

The plants include fen pond weed, stonewort, water violet, brookweed and golden dock, while the shallow water is buzzing with dragonflies, damselflies, water boatmen and pond skaters.

Prof Sayer added: "I think it is one of the most successful forms of ecological restoration I have ever come across.

"If you want to restore an ancient forest it takes a century, a meadow takes decades and rivers and lakes are hard to fix. But here, in two years, we have got stuff from an ancient landscape being preserved on farm land.

A clump of sediment containing pondweed seeds, which could be centuries old, from a 'ghost pingo' (Image: Denise Bradley)

"It might seem simple, but you can easily get it wrong. You need a lot of experts to get it right, because if you miss the seed bank, you don't get anything.

"You need experts in sediments, archaeology and geology for the mapping and surveys, and then clever excavation informed by that science."

The project has also restored four ghost pingos on neighbouring farms, and NWT has published a pingo restoration guide to explain the process to other landowners.

Jon Preston, conservation manager for the Norfolk Wildlife Trust, in one of the trenches cut across a 'ghost pingo' at Watering Farm, showing the layer where the pingo was filled in, and the original black sediment layer (Image: Denise Bradley)

Jon Preston, conservation manager for NWT, said: "Within the valley of Thompson Common, there are lots of pingos that have been lost over time, so we are working with our partners to find and restore these ghost pingos. These are unique in the UK and if you have ghost pingos on your land it is a real privileged position to be in. 

"When you get down to the black soil there is a dormant seed bank, and these plants come back to life. Perhaps we could even find an extinct plant in there, that would be amazing."

The project at Watering Farm is part of the Brecks Fen Edge and Rivers Landscape Partnership, with funding from National Lottery Heritage Fund.