While walking the South Downs Way last year, I came across the much-photographed pond near Ditchling Beacon. With its lone tree, almost symmetrical shape and expansive view from high on the ridge, I too was compelled to take its photo. However, I was also drawn to find it on a map, where I discovered it is just one of a series of small, round, blue dots spread across the Downs. My curiosity was piqued, why are there so many and why are they all roughly the same size and shape? Well, the answer to that question, I discovered, is that they are all dew ponds.
To understand, why we have so many dew ponds along the South Downs, how they differ from normal ponds, and their purpose within the wider environment, I met up with Steve Walker. He is the jovial Natural England Manager of Kingley Vale Nature Reserve, outside Chichester.
We met in West Stoke car park, for what was a part walk, part off-road safari tour of the reserve, to enable us to get around as many of the dew ponds as possible within the time Steve had available. I was a little apprehensive about leaving the car, as the car park has a reputation for vandalism. However, Steve explained that this problem has miraculously been cured by the arrival of Coop’s coffee van. Mike Cooper’s daily presence not only wards off the criminals but naturally provides users with a much-needed warm brew after a bracing winter walk. With frequent reports of cars being broken into in rural spots while people are out on walks, I can think of a few spots around Petersfield that could benefit from a Mike.
At our western end of the Downs, Kingley Vale is the place with the largest number of Dew Ponds. This is because of an ongoing restoration programme. A few years ago they were down to just one functioning pond, but have since added 4 more. In addition to these, there are several more on private land adjacent to the reserve, where farmers have been persuaded to join the project.
The first stop on our tour was to one of the latest additions. With it being relatively new and winter, there was little vegetation to obscure our view. It was therefore easy to tell it was a dew pond. It was an almost perfect circle with a very shallow outer rim. This allows grazing animals, such as sheep, easy access to the water. Steve explained that a typical dew pond is best described as ‘saucer-like’ in design, as even the middle of the pond is not terribly deep.
Dew ponds are not natural features, they have always been man made, with evidence indicating that construction dates back as far as the Bronze Age. They were built across the porous chalk Downs to provide water for livestock grazing up high. Whilst this is still the primary purpose of many ponds at the eastern end of the Downs, at Kingley Vale the ponds serve a wider environmental purpose. Not only do they provide water for deer and sheep but a breeding place for frogs, toads and dragonflies, and also food and habitat for a host of other species from grass snakes to bats. In periods of draught, these ponds are literally an oasis in a desert.
Traditionally, dew ponds were made from puddled clay and straw. But where does the water come from? With no source of ground water on chalk can they really be fed by dew? Back in Gilbert White’s day dew ponds were thought to be magical with their source of water the subject of great mystery and debate. Steve lay all this to rest by confirming that rainwater is their main source. However, he did explain that there is certainly a link between their construction method and name. The thick insulating layer of clay and straw creates a temperature differential between the ground and air above the water, encouraging dew to condense and settle in the early morning.
Unfortunately, a combination of climate change and accountants wanting long-term value for money, means that most new and restored dew ponds today are constructed with multiple layers of geo-textile underlay and butyl waterproof liners, as well as a final layer of clay for the plants to colonise. However, the good news is that the insulatory properties of this method still encourage dew to condense.
As we continued our tour of the other dew ponds around the reserve, it was clear that one of the main issues Steve contends with is people not appreciating they are visiting a nature reserve. With the dew ponds it is a combination of people throwing in invasive plants like duckweed, which can completely take over and are almost impossible to remove, as well as dogs using the ponds as swimming pools. This might seem a harmless bit of fun, but did you know that one flea treatment on a medium-sized dog contains enough pesticide to kill 60 million bees. Imagine the damage this can do to insect and amphibian life in the ponds. With sheep now grazing the site, to control invasive grasses and brambles and to help the creation of downland wildflower meadows, the rangers also regularly have to respond to reports of the sheep being chased by dogs off the lead.
Many of us are familiar with Kingley Vale as a great place to enjoy a leisurely walk, cycle ride or picnic. While it’s not easy to spot animals like dormice, adders, nightingales, hawfinches, and bats on these trips, it is important we remember this wonderful local resource is first and foremost a nature reserve providing protection to these endangered creatures. The dew ponds are just one string to the ranger’s bow in the quest for better biological diversity. The next time you visit the reserve, be sure to look out for the ponds, now you know what and where they are. However, I’d recommend going in the spring/summer when there are more obvious signs of life!
Image: Angela Tysoe