The Death of our Soils

Our soil is dying.

When you picture soil, you imagine rich, crumbling handfuls of moist dirt, the type that is soft, earthy, forgiving. At least, that is what soil should be – a mixture of rock fragments, air, water and organic matter, all cushioned in a bed of dark, fertile humus, and the billions of microorganisms that call it home. Living, thriving.

In reality, much of our soil is sick. It is dry and flaking, empty, lifeless. Plants cannot grow on it. Animals have nothing to feed on. Even the microorganisms buried far below are left hungry, slowly digesting what little organic matter is left. Yet all too often this travesty is ignored, despite our soil’s monumental importance.

We require soil to produce 95% of our food, both the crops we eat ourselves and those grown as fodder for our animals. As our population grows ever larger, this becomes more and more of an issue. Quite simply, without good soil, we will starve. It also provides the basis of many integral parts of our lives – from our wooden furniture to our cotton clothing, because soil is the source of nutrients for growth for the majority of all plants. Furthermore, it is a source of many antibodies, including the recently discovered class of malacidins, which managed to wipe out the well-known resistant Staphylococcus aureus (MRSA) in trials3.

Soil is also a carbon store. When plants photosynthesise, they turn carbon dioxide from the air into carbon forms which can be exchanged via their roots with organisms in the rhizosphere section of the earth, in return for other nutrients 1. Likewise, when they die, their organic matter is broken down by decomposers into different carbon stores. Although some of the carbon is used in respiration by these microorganisms, some is locked in an extremely stable form called humus, where it will remain for thousands of years if left undisturbed. Altogether, the top metre alone of our planet’s soils contain about 2500 gigatons of carbon – 3 times the amount in the whole of the atmosphere2.

But many of our agricultural practices are slowly degrading the soil, properly defined as any physical, biological or chemical decline in soil quality. For example, a reduction in fertility. When farmers plant one crop over and over – monoculture – they rob the soil of the same nutrients year upon year, leading to depleted stores of vital compounds and eventually rendering the soil too poor of a quality for farming. The same effect can be caused by over-grazing. Nature would normally return nutrients to the soil through the decomposition of dead animals and plants, such as crop remains, but nowadays fields are commonly cleared after each harvest. Farmers instead rely on artificial fertilisers to supply nutrients for crop growth, but these have their pitfalls. These synthesized products, alongside herbicides, cause chemical imbalances in the soil, such as pH changes, that eliminate many of the bacteria essential for soil and plant health – including the ones that form these symbiotic relationships with the plant roots, responsible for the transfer and lock-down of carbon into the ground.

The way we till our soil can also be harmful. The common practice of leaving fields bare over the winter increases levels of erosion by wind and rain, meaning precious nutrients and carbon stores are simply blown away into our rivers or seas. This is not only extremely wasteful, but additionally increases greenhouse gas levels. When soil is exposed to air, the carbon in it oxidises to become carbon dioxide, thus contributing to climate change whilst also robbing our soil of the carbon plants – crops – need in order to grow.

The shocking truth of it is that 33% of our soils are already considered moderately or highly degraded6, and every year, 24 billion tons of fertile soil are lost7– due to over-farming, excessive extraction of nutrients, erosion, pollution by chemicals, and all-round lack of respect for its delicate ecosystem and well-being. As our population increases, food security becomes more of a pressing problem, but it is estimated that at the current rates of damage, we have only 60 harvests remaining before our soils have nothing left to give8. Before they are depleted, left ruined, or eroded into the seas and lakes, their carbon leached into the atmosphere. Before they are spoilt by our poisons or simply worn out after years of intensive farming with nothing given back. If we do not start caring for our soils, there will become a point when they cannot produce enough food to feed us all.

But through simple processes, soil can be protected from the worst of the harm. ‘No-till’ methods of farming reduce the oxidation of the soil’s carbon by lowering levels of erosion; with it they also help conserve the nutrients we so desperately need for our food’s growth. Crop rotation and polyculture help avoid nutrient scarcity. Organic farming reduces the harm to the billions of microorganisms living below the surface. And finally, much-needed carbon and nutrients can be returned through the use of organic matter, which will also exploit soil’s potential as a carbon store.

All is not lost. But soon, if we do not act, our soil will be. And with it, so will humanity.

1. ‘Large-scale sequestration of atmospheric carbon via plant roots in natural and agricultural ecosystems: why and how’ Douglas B. Kell

2. ‘Total carbon and nitrogen in the soils of the world’ N. H. Batjes

3. Culture-independent discovery of the malacidins as calcium-dependent antibiotics with activity against multidrug-resistant Gram-positive pathogens”. Nature Microbiology

4. ‘The Effects of Chemical Fertilizers on Soil’ Irum Sarfaraz

5. ‘Quantifying global soil carbon losses in response to warming’ T. W. Crowther, K. E. O. Todd-Brown, M. A. Bradford

6. FAO Status of the World’s Soil Resources xix

7. Land and soil in the context of a green economy for sustainable development, food security and poverty eradication. UNCCD, 2012

8. ‘Only 60 Years of Farming Left If Soil Degradation Continues’ Chris Arsenault, December 5, 2014

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