Well, that is essentially the world beneath our feet. Soil is the Earth’s final frontier, and each small handful holds more living organisms than the number of people on the planet. We rely on it for nearly all of our food, for a stable climate and to stop rainwater running back out to sea. Yet across the world, we treat soil like dirt.
That wafer-thin skin covering the Earth holds a quarter of the world’s biodiversity. Worms, fungi and creatures teem aplenty, at least in healthy soils. Around the world, there are some 30,000 worm species and five million species of fungi that help bind the soil and soak up water. Soil even has its own microbiome containing at least a million species of bacteria.
We can only imagine how Nasa scientists would react if their Mars rover probes turned up anything like as much biodiversity. As it was, in the mid-1990s, the merest hint of life on Mars sparked headlines like “Mars lived, rock shows meteorite holds evidence of life on another world” and “Fossil from the red planet may prove that we are not alone”, all ignited by the most tentative evidence of fossilised bacteria from billions of years ago.
Yet the hidden world that we walk upon every day gets scant attention. Indeed, after 10,000 years of civilisation, much of the life forms that comprise our world remain unnamed. It was Leonardo da Vinci who said: “We know more about the movement of celestial bodies than about the soil underfoot.”
Five hundred years later, things haven’t changed much. What is even more remarkable is that this same hidden world holds the key to our own survival. Soil not only has a richness of life that would give any rainforest a run for its money, but it also stores carbon from the atmosphere, soaks up water and recycles nutrients, thereby holding our planetary life together.
That covering of topsoil across the world, with an average depth of about a foot, holds nearly twice as much carbon as the atmosphere. If we treat it well, it could hold even more, presenting a powerful piece in the jigsaw of how to solve the climate crisis.
The water stored in soil is the source for 90 per cent of the world’s agricultural production and represents about two-thirds of all fresh water. Soil holds that water close to thirsty plant roots, making for productive farmland. However, even moderately depleted soil holds less than half the amount of water of healthy soil. The rest runs off into rivers and streams and back out to sea, carrying nutrients and also chemicals that cause waterways to become polluted.
In worst-case scenarios, this leads to vast areas of sea or inland water becoming so polluted that nothing lives, creating dead zones. The more organic matter – carbon – in the soil, the more water it can hold. Healthy soils can stop homes flooding and prevent crops from wilting during drought.
As well as water, healthy soil supplies the nutrients and oxygen that crops require to grow. It also supports growing roots and protects them from extremes in temperature. If we treat it right, we could produce a lot more.
According to the UN Food and Agriculture Organization, with sustainable soil management we could produce up to 58 per cent more food. Yet instead, we choose an industrial approach that turns soil into the muck that we plant seeds in and where we feed them with artificial fertilisers. Many of the farm animals that once lived on the land disappeared inside factory farms, and those that weren’t were separated from crops and kept on farms specialising in beef, dairy, sheep, pigs or chickens. The concept of mixed farming became a thing of the past, as the chemical age of industrial, or ‘intensive’, agriculture was born.
Ploughing with heavy tractors and applying chemical pesticides to the land undermines the soil, disturbing ecosystems and releasing soil carbon into the atmosphere. Heavy vehicles compact the soil, so water flashes off rather than soaking in, making it harder for plant roots to find their way. In half a century, tractors have become six times heavier and compaction has become a big issue globally, affecting an area more than three times the size of the UK.
Artificial fertilisers kill bacteria and fungi that would otherwise break down nutrients and make them more available to plants, damaging natural soil fertility. The age-old nutrient cycle of rotating crops and replenishing soils with manure from free-ranging animals has all too often been abandoned. Long-held wisdom recognised the benefit of following soil-depleting crops like cereals with replenishing legumes that fix nitrogen in the soil. Of returning crop residues to the soil as green manure. Of resting tired soils under fields of grass to allow them to recover. Free-ranging animals would boost the regeneration through their manure, returning partially digested dead stuff to the living ecosystem beneath their feet.
The bottom line is that soil is a finite resource: if we carry on as we are, it will continue to degrade and disappear. Calculations suggest that soil is eroding up to a hundred times faster than it is being formed. A third of the world’s soils are already degraded, but such assessments are thought to be underestimates, because "intensive fertiliser application may be masking land degradation”. And things are getting worse – according to a review in Science , about one per cent of global land area is degraded every year. It goes on to warn of a “false sense of security” due to the “unsustainably high use” of fertilisers and irrigation.
All of this has a bearing on our ability to feed people. In 2015, the UN FAO warned that “unless new approaches are adopted, the global amount of arable and productive land per person will in 2050 be only one-fourth of the level in 1960”. Healthy soils are generally made up of five to six per cent organic matter, but half of Europe’s soils have two per cent or less. Much lower than that and yields could be affected.
Soils are degenerating at an alarming rate; relearning the secret of keeping them healthy is imperative if we are to reverse the trend.
This is an extract from the book, Sixty Harvests Left: How to Reach a Nature-Friendly Future, by Philip Lymbery