The sorry state of our soils

14 December 2015

Interview with

Professor John Quinton, University of Lancaster

We're dishing the dirt on one of the Earth's most precious, but declining plantsresources; it's not an animal or vegetable but a collection of minerals - more specifically, soil. 2015 was declared the year of soil by the UN, and this week they released a much-anticipated report on the state of the world's soils. Unfortunately the results aren't good. John Quinton is a soil scientist from Lancaster University and he joined Kat Arney to fill her in on what the report said...

John - The highlight from the report was that we really need to stop degrading our soils.  The report suggests that we're losing around a football pitch's worth of soil every five seconds, which is quite mind blowing really.  We also need to stop the decline in soil carbon, so soils hold onto about a third our carbon and we're losing that back up into the atmosphere.  We also need to rebalance the amount of nutrients in our soil, so some soils in some parts of the world have far too many nutrients and in other parts of the world they just don't have enough.  And then the final point that they make is just that some of the data that we have on our soils around the world is just really, really old and we need to update it.

Kat - And in terms of what we do know, given that the data is kind of old, what do we know about the kind of degradation that's facing our soils?

John - The kind of data that we have would suggest that around about a third of the world's soils are degrading, and the biggest threat to them is soil erosion.  So that's either by wind erosion where we've got dry soils, often in arid areas, which are just getting blown away, and then the other form is through water erosion.  So this again is when surfaces are exposed to the elements, and we get a heavy rainstorm, and it's actually washing the soil off hill slopes and down into the rivers and then perhaps out into lakes or even into the ocean.  So those are the two ones we're worried about in agriculture but we're also concerned about the area of soil which is being paved over.  More and more of us are living in cities and as we move into the cities, we cover the soil in concrete.  In Europe, an area round about the size of Cardiff is paved over every year, so that's another threat to the functioning of our soil.

Kat - So can we lay the blame really at the expansion of the population and the expansion of agriculture.  Are these the main drivers of the problem?

John - I think we are clearing a lot of land to produce food.  We're going to have what, around 9 to 10 billion people living on this planet by 2050 and they're going to need feeding and that's going to mean that we're going to need land to grow crops in them, so that's really going to be one of the big pressures and when you convert forest or grassland to agriculture, you degrade the soil.

Kat - And that, I guess, is the problem is what is the risks of losing so much soil like this?  Why should we care?  I mean it's just dirt, isn't it?

John - Just dirt.  Gosh, heathen.  It's the brown gold beneath your feet.  The living skin of the earth.  Scientists that around about 10% yield reduction by 2050 due to erosion, so that's equivalent to losing a 150 million hectares, is no longer going to be productive, so it's serious stuff.

Kat - But is just food that's at risk here?

John - So the other big concerns would be around carbon.  Soils store round about a third of the world's terrestrial carbon, so more than all the forests and all the atmospheric carbon combined so, if you lose the soil, you lose that store.  The other thing that soils do for us is to keep us supplied with clean water.  Most of the water that falls on the terrestrial surface is going to hit the soil before it ends up in rivers and lakes and so soils play a really important role in both buffering and attenuating the flow of water, but also of cleaning it up.  It's also packed with organic matter and soil micro-organisms and those things are actually, you know, pulling out all those nasty chemicals that we don't want to get into our water supply, and helping to produce clean water for people.  So that's another threat we need to be concerned about.

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