Ditches are man-made waterbodies that are used mainly to drain the land.
They are distinguished from streams in that they are usually straight, follow linear field boundaries, often turning at right angles, and show little relationship with natural landscape contours. It can sometimes be hard to separate them from heavily engineered small streams.
Where are they found?
There are over half a million kilometres of ditches in the British landscape – so they are found almost everywhere in the lowlands, and reach up surprisingly far into the hills as well.
What can you find living in a ditch?
Like all other freshwater, what lives in ditches depends on how polluted they are, and also on their gradient, and how often they flow. In lowland marshes around the coast, and up some river valley, ditches can have some of the most beautiful and richest freshwater communities – where they combine one of the great remaining refuges of comparatively unpolluted water, and very long history of wetland environments – they are the ancient woodlands of the water world. These are a minority, and are only found in a landscape which covers perhaps 10% of the UK. In the rest of the landscape, the ditches are much more like small, seasonal or permanent, headwater streams. Perhaps the most iconic species of the lowland marsh ditches is the Great Silver Water Beetle – our biggest water beetle and now almost entirely restricted to this environment.
Why are they important?
Ditches are important because some are truly outstanding gems of nature – as important as the very best salmon rivers for their wildlife. But they are also important because there are a lot of them, and they reach into every corner of the land. And although the smaller ditches ‘inland’ are not as rich as other freshwaters, you never know what temporary water specialists might turn up in them. And because there are so many of them, there’s a good chance that something will turn up in them that isn’t found in another freshwater habitat.
What we’re doing to help
We were the first organisation to systematically describe the importance of ditches for freshwater wildlife across the landscape – although the diversity of life in coastal marshland ditches has been known to many people, and carefully cherished by a range of organisations since at least the 1980s.
Now we’re focusing on making sure that the very best ditches – there are probably still thousands of kilometres – are protected from pollution, and that their quality is regularly monitored. Most are only surveyed intermittently, if at all. We’ll be starting practical projects to reduce pollution in the ditches systems around the fringes of the top sites so that sensitive creatures and plants can spread – not least because the coastal freshwater ditch networks are some of the most threatened by rising sea levels.
In the rest of landscape we’ll be looking out for the ditches which carry clean water as these will usually have the better variety of freshwater wildlife – and may support plants and animals associated naturally with headwaters.