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Rewilding water: using small water bodies to save freshwater life

Dr Jeremy Biggs is the co-founder and Director of the Freshwater Habitats Trust. Jeremy has over 25 years’ experience in the field of freshwater biology. His research interests focus on the maintenance of aquatic biodiversity at a landscape scale, and how different land management practices can mitigate the effects of pollution on the water environment. He leads several large partnership projects such as the Water Friendly Farming initiative and the Million Ponds Project. He is a member of the National Advisory Board of the Environment Bank Ltd, of the Research Advisory Group for the Defra Demonstration Test Catchments Project, and is a trustee of Wildlife and Countryside Link. He is also actively involved in the voluntary wildlife recording sector and is life member of the British Dragonfly Society.

How can you rewild the water on your patch? What will have the most impact? What will help the most species and what can you do if you own just one or two fields and don’t have 1000ha, or more, to play with? These are all question that Freshwater Habitats Trust is considering carefully in our work to protect freshwater biodiversity. And for us, it is the evidence of what works that is all important. Alongside this is recognition of some deep and long-standing truths about of freshwater habitats that often go overlooked.

For Freshwater Habitat Trust, one of the most important rewilding principles is the role of small waters, the small headwater streams, ponds, flushes and small wetlands that once dotted the landscape. Realising that small waters are vital, and not simply a nice to have optional extra, is only now beginning to be widely recognised by freshwater biologists. As one recent scientific paper by a group of European freshwater scientists noted drily:

‘new strategies should address the bias in research, management, and policy principally focused on rivers and lakes, largely excluding other freshwater habitats…[1]

In short, small waters are abundant globally, found in all environments from deserts to mountain tops and vital for protecting freshwater biodiversity. They are also vital part of the rewilding toolkit.

This means that perhaps the most important things to think about practically when rewilding water is your potential for making and managing small waters – which will usually be the majority of the freshwater you have to work with. The quickest, easiest and best evidenced impact you can have is with small waters, either by making them or by cleaning up the land that drains into them.

The second key principle for rewilding is that most freshwater plants and animals don’t just exist in rivers or in lakes or even in ponds or fens or springs. They usually make use of a network of habitats and the majority are mobile, as Charles Darwin first realised, and naturally exploit the dynamism of freshwater ecosystems. Overall, evolution has favoured species that can move from place to place following the freshwater habitats as they follow habitats that are rarely permanent in geological time but always present. But for the practical rewilder it’s also important to remember that some freshwaters and wetlands – like fens and bogs, or the old marshes of low-lying river valleys - are surprisingly ancient and often home to plants and animals that are less adept at moving around the landscape.

The third and most important thing that most rewilders can do is put clean water back in the landscape. In lowland western Europe where modem farming and urbanisation are common, it is hard to find clean water because so much of the land generates pollution. This is a particular problem for modern farming which it difficult, perhaps impossible, to do without causing pollution, compared to the quality of water running off of woodland, heathland or low intensity grassland.

The top priority for rewilders will nearly always be to create new areas of clean water. In much of lowland Britain this has largely gone: there are no unpolluted large rivers or lakes, and without complete societal changes this is not going to improve much in the near future. But you can add clean water by making new ponds and wetlands in places where they are filled by clean water. If you working on a bigger scale – say 500 ha and upwards – there‘s a chance that by eliminating intensive land use completely, you could clean up whole catchments of smaller streams and lakes.

Given the rarity of clean water, any waterbodies you make that are unpolluted are likely to be beneficial. But if you can make ten or 15 of them, that’s better than one, and if you have space for a hundred you will be starting to make a difference at the scale of the county or region. This is why big nature reserves, like those created by RSPB or others covering 50-100ha or more, have a substantial effect. Bigger spaces also give more space for clean water to persist or establish.

A final principle for rewilding is the role that big animals play in shaping the water, and this doesn’t just mean beavers! Big animals have helped to structure freshwater habitats for millions of years. Fossil dinosaur tracks show that big beasts have been trampling the edges of freshwater habitats for millennia, and it is no accident that in modern Britain one of the best things you can do for freshwater habitats, whether still or flowing, is gently trample and disturb the edges with small numbers of big beasts. In the modern world, often the best we can do is to use cows and horses. At low densities, it’s no accident that many of our best freshwater habitats are managed in this way. But a vital pre-requisite for this is clean water: polluted water trampled and disturbed day in, day out with an industrial intensity will be biologically depressing for the freshwater enthusiast.

The practical choices

There are two main reasons why small waters are such great value: they are collectively often the richest freshwater habitats in the landscape and in many landscapes support the most endangered species[2]. They are also easier to fix than bigger waters – because they are small, they have much smaller catchments than bigger waters, which means you are much more likely to be able to manage all of their catchments in the way that ensures it is really clean water than runs into your ponds and streams.

If you are trying to improve running water habitats, often the best things you can do are to work on the floodplain – where again there is more likely to be a chance of creating new clean ponds and wetlands, provided they are not too regularly flooded by, or directly connected to, the polluted water which is probably to flow down you river.

Of course, polluted water is not lifeless – and some plants and animals do best where pollutants are abundant (though this doesn’t apply to most declining or rare freshwater species). But landscape scale research shows that adding new polluted waterbodies – whether flowing or standing – doesn’t help bring back missing species much. This is because there’s already plenty of that polluted habitat in the landscape – you’re not really adding anything much that isn’t already there.

Life will be easier if you are in the less polluted uplands in the north and west of Britain (though you do still need to be aware that some land uses – like conifer forestry and modern dairy farming – can still cause substantial pollution). But here, simply making more water is likely to be beneficial. Don’t get too suckered into complicated schemes to put bends into rivers: although it seems intuitively obvious that these will be more diverse, ‘better’, habitats, there are dozens of detailed scientific studies from around the world showing that this kind if work has modest benefits, especially if costly. It’s probably better to focus on the floodplain and try to restore wetlands, ponds and pools here (though even these schemes which look very promising await thorough testing with good quality science). If you have unpolluted water in your straightened rivers, simply filling the channel in might be a good bet and letting the stream choose its own course.

Finally, think about where you are putting these new habitats. Will they be close to (but not necessarily directly physically connected to) places where species in danger of disappearing from your patch occur, to help stop local extinction? Will vulnerable plants and animals have any chance of spreading from nearby freshwater hotspots? Ask FHT or local specialists if there are special freshwaters nearby that you could help. Priority ponds, high-quality ditch networks, SSSI fens or bogs, rivers with Water Framework Directive biological groups classified as 'High status'[3] – these are all places to look for and ‘build out’ from. As local freshwater biodiversity hotspots you should be trying to create new habitats which species of these special places – often the only places they are hanging on in an area – can spread from.

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[1]van Rees, C.B., Waylen, K.A., Schmidt‐Kloiber, A., Thackeray, S.J., Kalinkat, G., Martens, K., Domisch, S., Lillebø, A.I., Hermoso, V., Grossart, H.P. and Schinegger, R., 2020. Safeguarding freshwater life beyond 2020: Recommendations for the new global biodiversity framework from the European experience. Conservation Letters, p.e12771. [2]Williams, P., Whitfield, M., Biggs, J., Bray, S., Fox, G., Nicolet, P. and Sear, D., 2004. Comparative biodiversity of rivers, streams, ditches and ponds in an agricultural landscape in Southern England. Biological conservation, 115(2), pp.329-341; Williams, P., Biggs, J., Stoate, C., Szczur, J., Brown, C. and Bonney, S., 2020. Nature based measures increase freshwater biodiversity in agricultural catchments. Biological Conservation, 244, p.108515. [3]In England, look at the Environment Agency Catchment Data Explorer to find rivers with invertebrates, plants or fish classified as ‘High’ status. These are biologically as good as it gets, and even if the river is still affected by pollution these High status biological communities are as good as it gets. Similar data are available for Scotland, Wales and Northern Ireland (and in the EU countries too).



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