SAVING THE SOIL
Almost half of the Earth's uppermost layer is now under threat. Can anything be done to save the planet's most valuable resource?
A
ANearly half the world's soil is in danger, a recent United Nations report warns, and unless the decline is slowed every scrap of farmable land could vanish within 50 years. Because roughly 90% of what we eat is grown in soil, which also supports human life in a range of less obvious ways, the implications are enormous.
B
BSoil scientists, notes Teodor Vaska of the Lindgren Institute for Ecosystem Studies in Uppsala, Sweden, have been sounding the alarm about soil degradation for decades, even as our appreciation of how much soil matters has deepened. Pack a single gram of healthy soil under a microscope and you may find several billion bacteria, along with viruses, fungi and other microorganisms, all of them at work among decaying plants and an assortment of minerals. Soil, in other words, does far more than feed us. It is the origin of almost all the antibiotics we currently rely on, and it may yet prove our strongest weapon against bacteria that no longer respond to drugs. It is also an ally in the struggle with climate change: as the microorganisms inside it break down dead plants and animals, the carbon those organisms contain is locked away, so that soil stores well over twice as much carbon as the whole of the atmosphere. On top of this, soil soaks up water and so limits flooding; in Germany, repairing the damage that soil-degradation floods do to buildings, roads and bridges costs around €280 million a year.
C
CShould soil lose the capacity to do all this, humanity would face serious difficulty. The threat is not that soil will vanish altogether, but that it will be stripped of the microorganisms responsible for its remarkable properties, and once they are gone, restoring them can take thousands of years. Farming is overwhelmingly the chief culprit. Where plants grow wild, the nutrients they draw from the ground are handed straight back when they die and rot; but humans rarely return the leftover parts of a harvest to the earth, so the soil steadily loses its fertility. Earlier generations found ways round this, rotating the crops they planted from one year to the next, for instance, or letting a field lie idle for a season.
D
DSuch methods, though, grew awkward as populations expanded and farming grew more commercial. The answer arrived early in the twentieth century, when the Brandt–Kessler process made it possible to manufacture synthetic nitrate fertiliser, and ever since farmers have been spreading it across their fields. Yet the wisdom of this has come into question over the last few decades. Applied to excess, chemical fertilisers can send polluting nitrous oxide into the air, while the surplus is frequently carried off by rain, washing nitrogen into rivers. More troubling still, we now know that using them without restraint damages the very soil they are meant to feed, leaving it acidic and salty.
E
EAmong those hunting for an alternative is Joren Maes, who began by running an orchard-care company in Flanders, Belgium, and today advises some of the leading soil scientists in the world. What he came to understand was that the surest way to keep his trees thriving was to look after the soil beneath them, and to that end he devised a mixture of helpful bacteria, fungi and humus*. When researchers at the Coelho Institute of Agronomy in Portugal spread this blend over plots ruined by years of over-fertilisation, plants sprang up that were vigorous not only above ground but below it, sending down roots tough enough to break through earth as hard as stone. In the control plots, by contrast, where only conventional fertiliser had been used, the handful of plants that appeared were feeble and stunted.
F
FInterventions of this kind, however, cannot on their own reverse soil degradation across the globe. Weighing up the choices worldwide first demands a reliable picture of which soils exist and what ails them, and that is no simple matter, not least because no international system for classifying soil has ever been agreed. Hoping to reconcile the competing approaches, the UN has launched the Global Soil Map project, in which researchers from eleven countries are jointly building a map tied to a database. Fed with readings from field surveys, drone flights, satellite images, laboratory analyses and much else, it is meant to deliver real-time information on soil condition. The team hopes that within five years it will have charted the world's soils down to a depth of 80 metres, and that the findings will be free for anyone to consult.
G
GEven this, though, is merely a beginning. What is still missing, argues Nadia Fournier of the Institute for Sustainable Land Use in Dunedin, New Zealand, are ways of framing the problem that make it register with governments and ordinary citizens alike. 'Scientists, on the whole, don't talk in a language policy-makers grasp — and the reverse is just as true.' The remedy she and her colleagues put forward is a target they call 'zero net land degradation'; much like the notion of carbon neutrality, it is simple enough to grasp that it can steer expectations and prompt action. For soils already at the edge, that may come too late, and a number of researchers are pressing for endangered soils to be placed at once inside protected zones. Yet even here there is a puzzle: should such reserves safeguard the places where soil is most diverse, or the stretches of untouched soil that might one day serve as a yardstick of quality? Whatever course we choose, saving our soils means acting without delay.
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Question 1 - 4
Choose ONE WORD ONLY from the passage for each answer.
Why soil degradation could be a disaster for humans
Fertile soil teems with microorganisms: besides bacteria, it holds viruses and 1. , all of them among decomposing vegetation and minerals. Soil does much more than feed us — it provides nearly all our 2. , and could prove crucial in resisting bacteria that drugs can no longer kill. By absorbing rainfall it shields buildings and roads from flooding, and by trapping 3. it helps to slow climate change. Should these microorganisms disappear, the soil's special qualities may be lost with them; the greatest single cause of such decline is the 4. that humans practise.