Why soil is important to life on Earth – and helps fight climate change

Soil is one of the most ubiquitous – and underappreciated – substances on Earth. Yet in several fascinating ways this miraculous substance holds the key to life.

Soil helps produce our food and unearth life-saving medicines and vaccines. Soil also filters and purifies our water, reduces flooding, regulates the atmosphere and plays a crucial role in driving the carbon and nitrogen cycles. It is also key to tackling climate change as it captures and stores vast amounts of carbon. Soil is also one of the most biodiverse habitats on Earth.

Although sometimes dismissed as “dirt” or “mud,” soil is often described by scientists as the Earth’s living skin: thin and delicate but also playing an irreplaceable role in preserving health of humans and the global biosphere. According to Professor Bridget Emmett of the UK Centre for Ecology and Hydrology: “Soil is one of the most underrated and little understood wonders on our fragile planet.”

Climate change and soil

Soil plays a vital role in either limiting or exacerbating climate change. Most people are already aware of the importance of forests and trees in reducing carbon dioxide (CO2) in the atmosphere. But soil stores an extraordinary quantity of carbon: three times the amount in the atmosphere and twice the amount contained in all plants and trees.

Plants extract CO2 from the atmosphere in a process called photosynthesis. Some of this carbon is then stored or “captured” in the soil as fresh plant residues and highly decomposed material known as humus. These organic compounds are highly enriched in carbon and are known as soil organic matter that locks carbon underground in a stable, environmentally friendly way. However, when soil becomes damaged or degraded, it can release CO2 or methane back into the atmosphere, thereby accelerating – rather than decelerating – the impact of climate change.

As John Scott, Zurich’s Head of Sustainability Risk, says: “This is why the way in which we use land for agriculture is so important. By switching from intensive farming methods to organic ones, for example, we could dramatically change the emissions profile of the land. If managed in the right way, soils will be healthier and more fertile – and also store more carbon.”

Soil is a vital stock cupboard – not just for carbon, but for the food we depend on.

Soil and food security

Biodiversity is essential to food security, both above and below the ground. Soil is one of the main global reservoirs of biodiversity to the extent that 25 percent of animal species on Earth live underground, while 40 percent of organisms in terrestrial ecosystems are associated with soil at some point during their lifecycles.

“There is a vast reservoir of biodiversity living in soil that is out of sight and generally out of mind,” says the University of Manchester’s Professor Richard Bardgett, the lead author of a report on soils by the UN’s Food and Agriculture Organization (FAO). “But few things matter more to humans because we rely on soil to produce food.”

Healthy soils provide habitats that support thousands of different species of fungi, bacteria and invertebrates, which then work in combination to drive the Earth’s carbon, nitrogen and water cycles, thereby creating the nutrients and food we need to survive. Simply put, soil produces a staggering 95 percent of humanity’s food supply, by growing both the crops we eat and the grasses and other plants that are fed to livestock.

Many life-saving drugs and vaccines from the last hundred years were discovered in the chemically rich and biologically diverse environments found in soil. These medicines range from well-known antibiotics such as penicillin, to bleomycin which is used to treat cancer and amphotericin that combats fungal infections.

Soil biodiversity also has an important medicinal role to play thanks to its relationship with plant roots. Healthy soils enable plants to produce helpful chemicals such as antioxidants which protect them from pests and other external threats. When humans eat these plants, the antioxidants they contain boost our own immune systems and hormone regulation. It is no exaggeration to say that there is a direct connection between healthy soils and healthy humans.

Why soils are in danger

When we are fully aware of the different ways in which soils helps to support life on Earth, it is doubly alarming to discover how damaged and vulnerable they have become. The FAO estimates that 30 percent of the world’s soils are now degraded. While a recent report by the European Commission estimates that between 60 and 70 percent of its soils are unhealthy.

There are multiple human-made threats to soil health. These include deforestation, urbanization, agricultural intensification, soil compaction, acidification, salinization, pollution, landslides, wildfires and soil erosion. According to the FAO, soil erosion poses a major threat to global food security and could compromise the wellbeing of at least 3.2 billion people globally.

What makes the situation even more serious is the fact that high-quality, fertile soils cannot be quickly or easily replaced. It takes 100 years to build just half a centimeter of healthy soil, which means we are currently losing soil 50 to 100 times faster than it is able to rebuild.

How to save soil

The largest threat to healthy soils is agriculture. Since the Industrial Revolution an estimated 135 billion tonnes of soil has been lost from farmland, through a combination of practices including deforestation to create more arable land, mono-cropping (growing a single crop year after year), overgrazing, tillage, the use of heavy machinery and the misuse of fertilizers and pesticides.

An important first step to minimize soil degradation is for countries to switch to “regenerative agriculture” practices. These include regular crop rotation, sustainable grazing and mixed-use farming methods such as agroforestry, which involves planting trees alongside crops. By changing the ways we farm, healthy soils can be protected from damage while degraded soils can be restored by growing a diverse range of plants.

Soil is connected to almost everything that humans do, including the plants we grow and nearly all the food we eat. This is why the changes required to preserve and restore it must be so wide-ranging. “Finding a remedy will require changes that extend far beyond the soil itself,” says John Scott. “It will involve changing the way we farm and potentially the whole nature of the agrochemical industry. It could also change the way we feed people all around the world.”

Raising awareness – both of the importance of soil and how it is currently at risk – is crucial in bringing soil health into the wider environmental debate. Until now, many of us have underestimated the richness and vitality of this unseen subterranean world.

Yet, according to Ellen Fay, the co-founder of the Sustainable Soils Alliance, its importance is hard to overstate: “Soil is crucial to the health of everything else. We can’t deliver on any of our environmental targets if we don’t deliver for soil – and we’re still a long way from doing that.”