Skip to 0 minutes and 12 secondsSo we've come to your experimental site in Cumbria where you've been working quite a few years on soil erosion. How big a problem is it? There are really two problems with soil erosion. One is for the farmer on site who loses his soil, the nutrients with it. The productivity of the crop is affected. And then there's a second problem, which is where the soil gets washed off into the streams and rivers and causes a pollution problem. In the UK, it's the latter one that we're normally concerned with. In some very local instances we could have very dramatic erosion, big gullies cutting through the landscape, causing a real problem for the farmer.

Skip to 0 minutes and 52 secondsBut the more common effect is on the water quality, rather than on the soil itself, and the productivity of the crop. But in other parts of the world, that's not the case. No, that's quite correct. So if you go to parts of southern Europe, or into Africa, South America, Asia, you'll find that erosion has a really serious effect on the productivity of farms and people's livelihoods as well. So the work that you've been doing here, what have you been doing? So what we've been doing is working with the farmer to try and find ways of preventing the sediment leaving the watershed and entering the main river and causing a pollution problem.

Skip to 1 minute and 33 secondsAnd so what we've done here is to construct a series of small wetland features in the landscape, into which the water flows from the surrounding land, and traps that sediment and stops it going off down the catchment and into the river. So one of those is behind us? Yeah, that's one of the wetlands that we've constructed. It's just been a ditch that's been widened out, which slows the flow down through the ditch, causing the sediment to drop out and be trapped. And that stops it then, reaching the main river and causing pollution problems there. So what kind of pollutants are we talking about? Sediment itself, but are there other pollutants that are important? Yeah, for sure.

Skip to 2 minutes and 17 secondsSo sediment is one, but associated with the sediment, we'll often find phosphorus, potentially pesticides, but also the loss of nitrogen and carbon from the system as well. And what other problems that causes, once it's in the water courses? OK. So phosphorus is a real problem in these low nutrient rivers in the north of England, and can cause problems such as eutrophication, which is the enrichment of those rivers. And we see a lot of weed growth and algal growth, which can cause problems for fish and other things. So can you show us how effective this particular feature has been? Sure, let's go and have a look.

Skip to 3 minutes and 1 secondSo what are we looking at here? So we've got here is top of the wetland. And you can see a big pile of sediment which has being deposited in that wetland. When we first dug these, they were 50 centimetres deep. And you can now see that you've just about got a few centimetres of water level. So in total, probably 10 to 30 tonnes of sediment is being deposited in this wetland. With all the associated phosphorous, nitrogen, pesticides, and carbon. And that's stopped them from going into the waterfalls, so very successful. Yeah, they're really effective measures for trapping sediment and sediment-associated pollutants.

Skip to 3 minutes and 42 secondsThe only problem with them is that you obviously need lots of them in the landscape if you're going to have a real effect on the water quality in the river. But overall, a good thing. And I guess it's something that farmers quite like because it doesn't take up too much space within their fields. Yeah. So this farmer has put the wetland into a nonproductive buffer strip on the edge of his field. And that means that he's not losing any yield from the main part of the field. And so he's quite happy to have these features on his farm. So this is very much a problem of a rural area, but in urban areas we'd see very different issues with soils.

Skip to 4 minutes and 22 secondsYeah, one of the big problems is soil sealing. That's really kind of the tarmacking over of soils, as we expand our urban conurbations in cities across the country, and across Europe, and the world. It's estimated that an area of soil the size of Berlin is tarmacked over every year in Europe. And obviously, once you've concreted over the soil, a lot of the functions that we've been looking at today are going to be impaired. Can you ever get them back, if you take that sealing away? I think it's very difficult, Carly. But there's really very little research that's been done into the functioning of urban soils.

Skip to 5 minutes and 4 secondsThank you very much for talking to us about your research, and some of the issues around soil security. It's been a pleasure, Carly.

More about the importance of soils

In this second part, John continues to talk about soil security and how his research is helping to protect soils.

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