Britain is Restoring Ancient Farmland ‘Ghost Ponds’. Here’s How They’re Recovering Its Dwindling Biodiversity

As reported below, in England the number of once-common farm ponds has dropped by half over the last few decades. Like beaver ponds, farm ponds are biodiversity “powerhouses”. Awareness of their ecological importance is growing, and private owners are leading restoration efforts.

 

NOTE: this article was originally published to BBC’s Wildlife Magazine.

Our farmland ponds have vanished, but new initiatives are bringing back these biodiversity powerhouses

HERE’S SOMETHING A LITTLE BIT MAGIC about restoring a pond. It might have been dormant for decades, reduced to nothing more than a misty hollow or an area of darker soil. Yet dig out the sediment of a so-called ‘ghost pond’, let it fill naturally with water, and life will return. The seeds of aquatic plants, resting still and silent in the seed bank, are woken from their slumber as if no time had passed at all.

Just a year after breaking open this biodiversity time capsule, the pond will be thronging with plant, invertebrate and amphibian life. After a few years, if vegetation is allowed to grow, it will be impossible to tell that the pond wasn’t always like this. As Carl Sayer of University College London (UCL) wrote in 2003, in a vivid and engaging paper on pond restoration: “The pond’s ghostly past will be all but forgotten.”

British farmland was once teeming with ponds. Whether occurring naturally in the landscape or dug for clay and marl for brickmaking and soil improvement, field and farmyard ponds were put to good use by agricultural communities. Ponds were places for watering livestock, soaking cartwheels and washing clothes in the days before mains water, and their fish and waterfowl were also an important source of protein.

But with the advent of modern agricultural and building practices in the mid-20th century, those ponds began to disappear. Enormous numbers were lost, filled in by farmers wanting to make the most productive use of their land, neglected because they were deemed to have outlived their usefulness, or poisoned by agricultural pollution. Sayer estimates that out of more than a million ponds in the late 1900s, only about 500,000 are left in Britain today. It’s a similar, or worse, story across Europe, with countries such as the Netherlands and Switzerland losing up to 90 per cent of their ponds in the last century alone.

This is a significant loss because the humble pond is actually a biodiversity powerhouse. It’s home to at least two-thirds of all wetland plants and animals found in Britain, which often support more species (including rare species) than other types of freshwater habitat such as lakes and rivers. These include invertebrates, from freshwater snails to dragonflies; amphibians, including great crested newts; all manner of nesting and foraging birds; and mammals such as bats, water voles and otters.

“Imagine measuring diversity with your feet,” says Sayer. “Walk through a wheat field and it’s quite low but as soon as you step into the edge of a pond, whoosh, it goes right up.” Alongside his role leading the pond restoration research group at UCL, Sayer is co-founder of the Norfolk Ponds Project, which works to reverse the decline. His surveys of Norfolk ponds in various stages of management reveal that managed ponds – those where mud has been removed and vegetation cut back, enabling light to reach the surface of the water and oxygen to circulate – have a higher diversity of aquatic plants and water beetles, as well as a greater abundance of plants and invertebrates.

The positive impact extends to vertebrates. A 2016 study by Sarah Davies, now principal research officer for wetland science at the Wildfowl & Wetlands Trust (WWT), found that open ponds harbour a much higher diversity of bird species.

But the power of ponds goes beyond their role as hotspots of biodiversity. “In the past there would have been what we call ‘pondscapes’, a network of ponds across the landscape,” says Davies. “These allowed wildlife that needs water to use them as stepping stones between larger water bodies. Nature has taken advantage of ponds.” (See box)

As with the loss of other key habitats for biodiversity, such as hedges and meadows, the decline in ponds has had a major impact on the range and abundance of wildlife on farmland. Populations of farmland bird species in the UK have declined by 58 per cent since 1970, according to a report by the Department for the Environment, Food and Rural Affairs (DEFRA).

So returning ponds to our agricultural landscapes can pay huge dividends in biodiversity terms. “Rewilding is our only chance to save the natural world because you can do things at scale,” says Sayer. “But some of that farmland will never be rewilded – it can’t be, because we need it to eat. That doesn’t mean we shouldn’t practise good nature conservation and that’s what this is: having these incredibly species-rich habitats in amongst the monoculture.”

Good nature conservation for ponds means cutting back vegetation every few years and, less frequently, removing built-up sediment with a digger. All ponds will naturally become terrestrialised – entirely filled in – eventually, with their lifespan dependent on multiple factors including positioning, drainage and rainfall levels. Even once they’re gone, traces of ponds remain discernible in the landscape, because of the presence of a stand of trees in an unlikely spot, for example, or a wet patch in a field.

“You can never not see them,” says Sayer, who coined the term ‘ghost pond’ to describe the phenomenon (a ‘zombie pond’, on the other hand, is one that’s so overgrown it’s effectively lifeless). That said, red herrings do sometimes arise, so ghost-pond hunters confirm hunches by consulting old maps.

TAKING A DIGGER TO A GHOST or zombie pond may look drastic – “It’s like a war zone when you’ve finished,” Sayer admits – but this work is simply a matter of mimicking natural processes, such as flooding or the activity of beavers. “Once we’ve mimicked it we then, to a large extent, allow nature to recover that pond,” he continues. “It’s a completely natural recovery but we’re having to provide this periodic disturbance.” The Norfolk Ponds Project has so far restored more than 200 ponds in this way, and influenced the restoration of countless more.

Overgrown and terrestrialised ponds can still play a valuable role in the landscape, however, as habitats for some woodland bird species. “It’s about creating variety,” explains Davies. “Ideally, you want multiple ponds on your land restored at different times, and different features at each pond so that you can benefit the greatest amount of species over a whole landscape. The beauty of ponds is that they’re all so different.”

This past spring saw the completion of the WWT’s Flourishing Floodplains project, a two-year partnership with the Open University and the Farming & Wildlife Advisory Group South West (FWAG-SW), to restore vital habitat in the Severn and Avon Vales. The project created or restored 42 farmland ponds and scrapes (small wetland features that tend to dry out in the summer), taking the first steps towards undoing some of the damage of the past 100 years – between 1900 and 2019, the number of ponds in the area fell to 6,630, a drop of 39 per cent. (While restoring a pond is the quickest way to boost biodiversity, creating one from scratch offers the same benefits, just over a longer timescale.)

“We looked at how what we were doing would offer benefits within the landscape and existing wildlife areas,” says Sarah Wells, senior farm environment adviser at FWAG-SW. That included restoring habitat on an estate between WWT Slimbridge and Walmore Common, a Site of Special Scientific Interest (SSSI) on the Severn floodplain. This habitat will act as a stepping stone between the two reserves. The project also restored ponds on land adjacent to existing nature reserves to serve as overspill habitat for birds during winter flooding.

IT’S HOPED THAT THE LEGACY OF THE Flourishing Floodplains project will be to encourage further pond restoration work in the Severn and Avon Vales. For that to happen, landowners will be a key piece of the puzzle. Fortunately, Wells says, “Farmers are really up for the restoration of ponds”.

Debbie Wilkins, for example, who had five ponds and scrapes restored on her family farm near Gloucester as part of Flourishing Floodplains, sees this work in terms of her responsibility as a landowner: “I want to look after it the best I can and share it with the biodiversity and wildlife,” she says.

The challenge, as is so often the case when it comes to making our agricultural land more wildlife-friendly, is getting the numbers to add up. “Ponds are a great asset to farmland and we are encouraging the creation, restoration or management of ponds across the farming sector,” says Mark Spencer, Minister of State for Food, Farming and Fisheries. “We are paying farmers who are taking action to manage ponds through our Countryside Stewardship scheme.”

Yet there are questions as to whether these funds are sufficient. While it might cost a farmer around £3,000 in labour costs to restore a pond measuring 10m by 10m, Wells explains, the incentive available via the government’s scheme, designed to recompense landowners for land lost to crops, is £282.15.

“It just doesn’t touch the sides,” Wells continues. “The footprint of a pond is quite small so it means that there is little in terms of income forgone from cropping because it’s only taking out a small area. But actually the wildlife benefits of having farm ponds are felt across the wider landscape. I hope we’re able to use some of the research that WWT is developing to demonstrate to policymakers that ponds need to be valued more highly.”

In the meantime, it’s a matter of farmers covering the costs of pond restoration or finding alternative sources of funding, such as the schemes set aside for conserving great crested newts.

However they make it work, there’s no doubt that pond restoration is well worth the effort. As John Sanderson, a Suffolk farmer who restored 16 ghost ponds on his land last autumn, puts it: “It gives us an instant fix in terms of biodiversity. There are plants coming up from the seed bank in ponds that have been filled in for maybe 70 years, and longer, which is exciting. They’re like little time capsules.” 

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