Are our soils in crisis?

To mark this year’s World Soils Day, ADAS Soil Scientist Anne Bhogal reflects on the importance of prioritising soil health.

We rarely pay much attention to it, but the soil beneath our feet is the foundation of all Earth’s ecosystems. Healthy soil is full of life – just one kilogram can contain more organisms than there are humans on the planet. It is a precious resource that can take thousands of years to create naturally.

Our living soils provide us with what scientists describe as a range of important ‘ecosystem services’. These include supplying our food and fibre through agriculture; storing carbon and regulating our climate; controlling the flow and quality of water; and supporting much of the planet’s biodiversity.

“Despite all our accomplishments, we owe our existence to a six-inch layer of topsoil and the fact it rains.” – Paul Harvey (1978) U.S. radio broadcaster

Soils are highly variable, even within small geographical areas (there are over 700 different soil types in the UK alone!). This affects what habitats they support and ultimately, how they are used. For example, while lowland mineral soils under arable and grassland management are important for food production, deep peats in upland areas under semi-natural habitats are important for carbon storage and climate regulation.

Soils contain about three times the amount of carbon held in the atmosphere and are the largest terrestrial carbon store. They therefore play an important role in regulating the balance of greenhouse gases (GHG). Disturbing soils through drainage and cultivation causes the release of carbon dioxide. It is estimated that cultivated (or arable) soils have lost up to 60% of their carbon compared to their ‘natural state’. This not only has consequences for the climate, but also has impacts on wider soil functioning. Protecting and improving soil health is therefore essential for sustainable food production and food security, water quality and flooding, as well as helping to mitigate climate change.

Why is soil health declining in some areas?

The recent UN ‘State of soils in Europe’ report highlights the significant impacts of soil degradation on agriculture, ecosystem resilience, water quality, biodiversity, and human health, underscoring the urgent need for comprehensive soil management strategies.

In the UK, the main soil degradation processes of concern are compaction, erosion and loss of soil organic matter (or carbon). These cost in the region of £1.5 billion a year in England and Wales.

Biological processes drive the majority of soil ecosystem services, underpinned by soil organic matter (SOM) decomposition. Organic matter provides a food source and habitat for the soil biological community, drives the cycling of nutrients within soils and is a central component of soil aggregation and the maintenance of structure and water relations. SOM is therefore fundamental to the maintenance of soil fertility and function and is a key indicator of soil quality.

There are many factors that can cause declining soil health, including:

• land use change (e.g., grassland cultivation, peatland drainage and deforestation), resulting in a loss of SOM
• damage to soil structure from suboptimal agricultural field operations and livestock grazing, when soils are wet – this is particularly problematic with late-harvested crops in the UK that can result in severe soil compaction and erosion
• contamination and nutrient enrichment from poor nutrient and waste management
• urbanisation and soil sealing reducing the ability of soils to regulate water flows and reduce flooding risk
• extreme weather events, such as high winds and rainfall, which can lead to significant erosion, compaction and flooding.

As soils become degraded, they are more vulnerable to erosion and are less able to provide the ecosystem services we all rely on.