This month, rangers at Wicken Fen National Nature Reserve (NNR) in Cambridgeshire, cared for by the National Trust, will turn on taps across the site to allow water to flow from the lodes on higher ground to the lower laying fens, creating standing pools of water to create a winter wetland for wildlife, as well as sequestering carbon.
A significant moment in the year for the site, the added water helps create wetland conditions for the winter months that will attract wildfowl including wigeon, teal, shoveler, gadwall, geese, egrets and sometimes whooper swans.
Ajay Tegala, Ranger at the National Trust’s Wicken Fen, explains: “We have six taps which we turn on using a metre-long metal key, allowing water to flow through a pipe onto the fens. Because the lodes are higher than the surrounding ground, gravity enables the water to flow without having to resort to pumping."
“There is immediate visual impact as water rushes through and swells up, forming a sort of miniature fountain. Then, water can be seen flowing."
“A couple of days later, the spectacle continues when the standing water starts to attract a huge variety of wildfowl who find food and safety in these wetland areas. Roosting on water overnight helps them feel protected from potential predators, for example foxes, that are potentially put off by having to wade through water. A flowing river could wash birds away while they rest overnight, but the shallow depth of water on the Fen means that its relatively still, creating an ideal habitat.”
Turning on the taps for winter also helps to restore rare fenland habitat that was lost due to agriculture-related drainage centuries ago, reinstating higher water tables that support wetland birds and wildlife and boosting biodiversity at this internationally important NNR.
To date, more than 9,300 species, including a spectacular array of plants, birds and dragonflies have been recorded at Wicken Fen, making it one of the most species-rich places in the UK.
The process of turning on the taps also helps mitigate the effects of climate change by improving the area’s ability to store carbon. Re-wetting or flooding peat soil enables it to sequester, or lock in, carbon, rather than it being released into the atmosphere. As found by an academic study published in the Journal for Agriculture, Ecosystems & Environment, re-wetting a part of the NNR called Baker’s Fen, an area of grassland grazed by herds of highland cattle and Konik ponies about one mile from Wicken Fen Visitor Centre, lead to a reduction of the area’s CO2 emissions by 80%.
Over the last nearly one hundred years, the process of re-wetting has been monitored, and over the last thirty years water levels have been measured using dipwells at over seventy locations on the wider reserve. But in recent years, the site has faced new challenges in the form of weather extremes, such as the heatwave and drought last summer, which have added strain on the recovering peatlands.
Alan Kell, Countryside Manager for the National Trust at Wicken Fen, said: “The abstraction we create by turning the taps is a great way to create fantastic winter wetland habitats, protect our peat soils and help them lock up carbon. Unfortunately, it’s a technique we can only employ during the winter months as there is insufficient water in the summer months.”
The optimum water table to protect peatland soils and minimise carbon emissions falls on average between -10 to -30cm. But last year the water table dropped to a perilously low level of –1.6m on the undrained area of Fen at Sedge/Verralls Fen, which contains peat depths up to 4m. The low water levels will have caused the peat to oxidise and release carbon instead of sequestering it.
Alan continues: “We know that Wicken Fen has a big role to play for climate action, but without sufficient water, it can quickly go from a fantastic carbon sink to a terrible carbon source. With droughts anticipated to become more frequent combined with the pressures of continued development and its associated water use, the availability of water is and will continue to be one of the biggest challenges to this site."
Wicken Fen was the first nature reserve acquired by the National Trust in 1899 and has grown from two acres to a reserve that now covers over 2,000 acres to benefit both wildlife and people. The raised boardwalk and lush grass droves allow easy access to a lost landscape of flowering meadows, sedge and reedbeds, where visitors can encounter wildlife such as hares, roe deer, water voles and bitterns.
Wicken is also one of the last remnants of undrained fen in East Anglia and has important environmental designations, and in addition to being National Nature Reserve, is a Site of Scientific Interest (SSSI), Special Area of Conservation (SAC) and a Ramsar wetland of international importance.
Following this year's re-wetting, visitors will be able to enjoy a real wildlife spectacle through the colder months and admire the sight and sound of hundreds of birds that would otherwise not be at Wicken Fen, including hen harriers, cranes, bitterns.