Written By Becky Searle, soil and gardening expert.

For centuries, the soil has been regarded as dirt beneath our feet. Most of us haven’t given it a second thought. But with advances in technology and science, we now understand so much more about the fascinating world of soil and why soil health is so important. 

The soil is thought to be home to over half of the world’s species. This makes it the most biodiverse habitat on the planet. It also hosts around 50% of bacteria on Earth, 85% of the world’s plants, and over 90% of all fungi. 

The soil ecosystem is so delicate that many of the tiny organisms in the soil never survive the journey to a laboratory. This led many historical studies to conclude that soil was an inert substance containing earthworms, beetles, and plant roots. 

Why is The Soil Ecosystem so Important?

The soil is an incredibly important resource. We rely on it to produce around 95% of the world’s food. Soil can help to prevent flooding by slowing and storing rainwater. It stores more carbon than all of the world’s trees and has the potential to hold a lot more. Soil is also responsible for directly or indirectly supporting all terrestrial life. Additionally, it plays a significant role in global nutrient, energy and climatic cycles. Without healthy soil, the earth cannot regulate. And the health of other ecosystems – even those that do not directly grow from the soil will be affected. 

Critically, soil can do all of these things without human intervention and conservation. In fact, the soil’s ability to rebuild and regenerate itself is something of a marvel compared to most natural ecosystems.

Unfortunately, many of the world’s soils are at risk of irreversible damage. This is partly due to intensive farming using ploughing and chemical spraying. Arable agricultural fields are the most at risk. Some estimates say that even with the addition of chemical fertilisers, many are likely only to withstand another 60 harvests. Pollution and degradation of other habitats also threaten the safety of our soils.

How Does The Soil Work?

Like all ecosystems, when they are in good health, they exist in a state called dynamic equilibrium. This is a way of describing a system that is in balance but constantly shifting and changing to cope with outside influences. It means that healthy ecosystems can recover from events such as flooding, drought, the arrival of a new species or even fire, given enough time. 

In the case of the soil, structure is key. Subterranean life can be a challenge, so the organisms living in the soil work tirelessly to maintain a healthy environment. Whilst some soils, such as peat bogs, work a little differently, for most this means creating good drainage and an ability to hold water as well.

Particles in the soil hold water like tiny sponges whilst air sits in the spaces between the particles. Healthy soils, rich in organic matter can filter water quickly through the layers of the soil, protecting downstream ecosystems. Also, because the majority of plants rely on a steady source of water, the ability of the soil to hold water directly affects plant growth and health.

Dynamic equilibrium relies on biodiversity; the more biodiverse the system, the more likely the unique species needed to aid recovery will be present. Because much of the life in the soil is made up of microbes, the rate of reproduction is very high. This means that soils can repopulate quickly and start the process of rebuilding good structure. The only thing they need is live plants or dead organic matter on which to feed. 

What Ecologists Need to Know

Soil health certainly has the potential to solve many of the world’s current challenges. For ecologists, the primary concerns for wildlife now are climate change and species loss. Healthy soil is critical in supporting biodiversity. Moreover, as one of the most biodiverse ecosystems on the planet, it should be a key focus for conservation efforts. 

The soil’s potential to capture and store carbon, alongside plants, also makes it key to stopping or even reversing climate change. It has been estimated that restoring the world’s soils could remove up to 5.5 billion tonnes of greenhouse gases from the atmosphere every year. The best part is that the more carbon-rich the soil becomes, the more biodiversity it can support. As soil health improves the more effectively it functions. 

Soil also helps to regulate the water cycle. Not just by absorbing and slowing floodwaters, but also by working as a giant storage and filtration system. Many other habitats are silently protected from pollutants because of the superb work soil does at filtering and purifying water.

What Happens if The Soil is Unhealthy?

Unhealthy soil falls apart easily. This was seen on a grand scale during the Great Dust Bowl in 1930s America. Soils were disturbed by ploughing to a point where they could no longer hold their own structure. Particles formed great clouds over the prairies, posing a huge risk to life, coating lungs, cars and houses and causing havoc. This should have served as a stark warning. And it did indeed precipitate several government-led initiatives to prevent soil erosion.

Nowadays, soil erosion happens on a smaller and less noticeable scale. But the effects are no less pervasive, choking freshwater and marine ecosystems. But soil degradation also leads to a lack of healthy soil, meaning more difficulty producing crops to feed ourselves. It also means that protected areas are vulnerable to contaminated run-off as more chemicals are needed to produce food. 

How do We Build Soil Health?

Building healthy soil is relatively straightforward since most of the work is done by the soil organisms themselves. It is done in the same way as rewilding, by allowing nature to run its course and giving it gentle encouragement if required. We need to ensure soil organisms are fed and protect soils from disturbance. 

Soil organisms must have access to organic matter to eat. This can come from live plant roots, animal faeces or dead plant matter. In natural ecosystems, organic matter is constantly cycled through the soils as plants drop their leaves, and the soil organisms break them down and return the nutrients to the plant. Plants also actively pump organic matter down through their roots to the soil organisms to feed them. Some plants give away as much as 40% of the carbohydrates and sugars they produce during photosynthesis to feed the soil. This is remarkable because it shows us how much plants value the life in the soil. 

As ecologists, we learn that areas with no soil, such as newly formed volcanic islands and sand dunes, can even be colonised by plants. These plants are called pioneer species, and they start the process of topsoil creation so that other plants can move in. We can allow this to happen on very degraded soil or speed up the process by sowing seeds of plants that require few nutrients to survive, such as prairie and meadow plants. 

Getting the Balance Right

Of course, we must also develop soil-positive ways to farm and produce food. This is increasingly being recognised, and regenerative agriculture is a movement that seeks to develop and expand this to the mainstream. 

Soil health should be considered in all conservation efforts, particularly concerning freshwater and marine ecosystems. It is therefore important that conservation workers and ecologists understand the importance of healthy soil, and how to create it and protect it. 

Tips for Building Soil Health

Here are a few things that we, as ecologists, can recommend to protect from soil degradation and erosion and build soil health:

• No chemical sprays, including pesticides, herbicides, fungicides and chemical fertilisers. All these chemicals upset the natural balance of the soil, and interrupt the plant’s interactions with the soil. Fertilising with manure is a good alternative for farmers, but be aware that many farm animals that are kept indoors in close quarters are fed wormers and prophylactic antibiotics that could harm the soil. 
• Stop ploughing or digging. Small-scale digging, for tree planting for example, is necessary and fine. Repeated and large-scale digging, such as ploughing, should be avoided. Research no-till and regenerative agriculture. I recommend starting with ‘Dirt to Soil’ by Gabe Brown as this documents a large-scale mixed agricultural plan that helps to restore soil. Remember that switching to no-till farming can be extremely costly for farmers as it requires new equipment. As this practice is developed and becomes more mainstream, this equipment should be more readily available to borrow, but currently, this remains a hurdle for most farmers. Soil health is directly and seriously affected by long-term regular disturbance.
• Try to keep live plants in the ground as much as possible. Cover crops and green manures can help protect agricultural soils during winter when runoff and erosion are at their worst. Ensure that the crop being recommended is suitable for the area and will not be invasive. 
• Rewilding. Where possible, letting soils regenerate on their own with little or no intervention is a practical, long-term solution. This will help to gradually build topsoil and establish communities of plants and animals well suited for the types of soil available. I recommend taking the Rewilding course from ETUK and reading the book ‘Wilding’ by Isabella Tree. 
• If you are working with bare soil that will not be used for agricultural purposes, you can consider planting it. Choose plants with varying root depths and canopy heights and ensure that they are suitable for the soil type and environmental conditions. 
• Extra care should be taken when working with soils close to riverbanks, as runoff and erosion can cause severe damage to aquatic life. 
• Adding organic matter to the soil in the form of good organic manure or compost helps to feed the life in the soil and improve soil structure and function. This is a good way to speed up soil improvement and prevent erosion, but it should be coupled with the above advice. Do not deposit manure or compost near a waterway as it can leach large amounts of nutrients and cause eutrophication.
• Fungi are an integral part of soil health and arguably its most important component. If you wish to give soil care advice, it is critical that you understand the important role that fungi play within the soil. ETUK’s Fascinating Fungi course is a great way to learn about fungi and gain a deeper insight.