Soil, The Indispensable Dirt

Beneath our feet, out of sight and often out of mind, soil is probably the least appreciated source of human well-being and security. More than simply a prerequisite for farming and food production, it is a complex web of interactions that in turn enables many of the Earth’s life support systems to function.
To grasp why soil is so important, one must first understand what it is made of, namely weathered rock, air, water and organic matter — both dead and alive. Despite only making up approximately 5 per cent of the total volume of many soil types, organic matter fulfils an array of roles from maintaining soil structure to storing a proportion of water far in excess of its own weight. The living diversity held even within a small amount of soil is dizzying — ten grams of soil from a healthy arable landscape can be home to more bacteria than there are people on Earth, and that is before you begin to count the fungi, protozoa and more familiar inhabitants present such as earthworms and insects.
What Does Soil Do?
Through the functions carried out by the organic matter within, soils deliver clear and essential benefits for humankind. Over 95 per cent of our food depends on functioning soil for its continued production, as does the freshwater supply for most of the world’s population. A single hectare of healthy soil has the potential to store and filter enough water for 1,000 people and with climate change causing ever more frequent droughts, this capacity of soils to store water will be an increasingly important factor for crop productivity, and indeed food security as a whole.
That organic matter is also rich in carbon, and the more of it there is in the soil, the less carbon dioxide there is in the atmosphere. By maintaining soil health, we therefore not only help to secure water supplies and food but also can make a contribution to both fighting and adapting to climate change.
Despite all of this, for many people soil has taken on the cultural label of ‘dirt’. It is for many of us something to be avoided, washed off, sealed beneath another surface or treated to liberal doses of industrial chemicals to make it useful. None of this is rational and it is time to change our perspective.
With the vast majority of global food supplies depending on soil, it seems all the more remarkable how we abuse it, compacting and eroding these complex systems, causing that vital organic matter to be depleted and soil health to decline. We have masked these changes by using more industrial fertilizers and pesticides to promote plant growth and in the process caused other environmental effects that we are still only beginning to grasp. For example, what pesticides do above ground has to at least some extent been investigated, and so has the impact on larger soil creatures, such as earthworms. We know far less, however, about the effects of pesticides on those smaller soil organisms which play such vital roles in performing the ecological miracles that enable the plant growth that supports life on land.
Even the physical act of cultivation causes not only a degradation of soil health but can pose risks to human health and well-being. As soil is compacted by farming machinery, it can no longer effectively circulate air or water through the soil profile. Not only does this cause soil to become drier, but it also increases the risk of flooding as water that would have once been absorbed instead runs off to watercourses all at once, rather than being stored within the soil for a slower and more gentle release.
Soil is under pressure, and its ability to provide a full range of essential goods and services has been reduced, in some places quite dramatically. The loss of topsoil is one of the most serious symptoms of soil degradation and is regarded as a major problem in many regions, including China, parts of the USA and Australia. According to one authoritative estimate, an area of agricultural land about 10 times the size of the UK has been degraded to the point where it is effectively of no use for cultivation. In parts of the United States, soil is being lost ten times faster than it is being replenished; in parts of China and India, it is estimated that this increases to a factor of forty. Globally at least 24 billion tonnes of topsoil is estimated to be lost each year.
What can we do?
Much of the above can be linked back to one overriding and pressing the environmental issue — our food system. The global shift to industrial farming methods based on monocultures and high levels of input, in large part geared to sustaining Western-styles diets, including high consumption of cheap animal products, has changed farmed landscapes. Livestock bred for human consumption is often fed a lot of soya and maize — today around 75 per cent of these crops’ production worldwide is used in animal feeds. The British livestock industry alone needs an area the size of Yorkshire to produce the Soy used in its feed.
Despite this continuing shift, we are producing enough to feed the world’s human population. The problem lies in overconsumption, particularly of animal protein, and this presents the greatest challenge to achieving a food system that would feed everyone in a way that the planet’s soils could sustain. In 2009, over a quarter of the world’s population lived in regions and countries that ate more animal and plant protein than is nutritionally recommended. If these 2 billion people ate only the amount of animal products recommended to suit their nutritional requirements, then total agricultural land use would decline by 13 per cent — an area of land (soil) approximately twice the size of India.
On top of this is the challenge posed by food loss and waste. About one-third of grown is never eaten, meaning that a vast area of soil is producing food for nothing. Combatting food waste could thus cut a lot of the pressure on soils.
In addition to action by consumers to reduce livestock-based food and to avoid food waste, we can all encourage our political representatives to change policies so that farmers are incentivized and supported to do better for soils. This would include farming methods that increase organic matter, not leaving soils bare during heavy rain and using animals as part of mixed and sustainable rotations in the place of massive monocultures. All of this can be done and increasingly we can see the reason why.
Soil may have for many of us been out of sight, but it cannot for much longer remain out of mind. So, on World Soil Day, today 5 December, and indeed on every other day, spare a thought for that indispensable dirt and what you can do to help preserve it and all it provides for future generations. It’s probably the most important thing we never really think about.