Unlocking the carbon storage potential beneath our feet

Climate change is the defining challenge of our age, but the real battleground may be under our feet. Soil, the planet’s second-largest carbon store after the oceans, holds more than all the world’s forests combined. Mismanaged, it leaks vast amounts of greenhouse gases. Managed well, it locks carbon away (as part of the carbon cycle) for generations, confirmation that how we treat the ground beneath us, could mean that the difference between climate success and failure – and it is about time that we started paying attention - argues Robert Wilkins, operations director at Ruskins, the soil and tree specialists.

Soil is a complex mix of minerals, organic matter, microbes, air and water. Within that mix lies one of the planet’s largest carbon stores. Globally, soils are estimated to contain about three times more carbon than the atmosphere. Every time we disturb or degrade  soils, whether through construction, farming or careless landscaping, we risk releasing some of that carbon back into the air or reducing its ability to store carbon. But when we manage soils well, we can protect existing carbon stocks and even increase them, turning the ground beneath us into a powerful ally for climate action.

Yet everyone was blinded by the increasing expensive and impossible route to Zero Carbon, that consigned anything with a whiff of offsetting to the naughty cupboard. Where as improving soil health is the easiest, cheapest and most effective way to reach net zero (perhaps excluding the low hanging fruit of closing coal powered power stations).  

Net zero means balancing the carbon we emit with the carbon we remove or offset. While reducing emissions is rightly the top priority, there will always be some activities that release greenhouse gases. To compensate, societies must find ways to capture and store carbon. Forests and peatlands are often mentioned in this context, but soils cover far more ground and offer enormous untapped potential.

A hectare of healthy soil can store many tonnes of carbon, locked up in organic matter from plant roots, decayed vegetation and microbial activity. Practices that build soil organic matter not only store carbon, but improve fertility, water retention and resilience to erosion. This is why builders and developers need to understand soils, to either avoid degrading them or to enhance them in the final landscape. This will help to support new soft landscapes as nature intended, with the added advantage of better drainage and storing more carbon (and boosting biodiversity).

Soil carbon under threat

The problem is, that much of our soil is already degraded. Centuries of intensive farming, widespread sealing of land under tarmac and concrete and repeated disturbances from construction have left soils depleted.

In the UK, it is estimated that whilst UK soils hold around 9.8 billion tons of carbon, so much of it is now degraded, that it now holds only 50 per cent of what could be possible according to a report by House of Lords Science and technology Select Committee.  The UK Construction sector also destroys 10 times the amount of soil lost in the UK through erosion, every year claimed the Soils in Planning and Construction Task Force in September 2022.

Every time topsoil is stripped away or compacted by heavy machinery, stored carbon is lost. Drainage of peat soils in particular have released huge amounts of carbon, turning natural sinks into sources of the material.

As  we are only beginning to understand soils, their ability to store carbon is just one of their functions that is not widely appreciated. In addition, the focus on zero Carbon and the widespread lack of understanding about soils, has largely ignored the fact that soil, when treated properly, has the ability to reverse climate change.

This matters because degraded soils cannot perform their climate function. Instead of acting as a carbon bank, they become a liability. That is why soil protection is increasingly recognised in climate strategies and why land managers of every type - from farmers to developers - are being asked to rethink how they treat the ground.

Construction, in particular, may not be the first industry people associate with soil health, yet its impact is enormous. Large projects involve excavation, compaction and movement of soil, all of which affect carbon storage. Traditionally, soil has been treated as waste material to be shifted, dumped or simply ignored, but thankfully that attitude is changing.

Forward-thinking contractors are now incorporating soil management plans that retain the health of soils into their environmental strategies. By minimising disturbance, segregating soil types on site and ensuring that stripped topsoil is reused rather than discarded, they are reducing carbon loss.  However, the storing of soils in soil heaps, degrades the Soil Biology within them and their ability to store carbon.  More innovative approaches such as applying Soil Biology when planting final landscapes, creating green roofs, living landscapes and biodiversity-friendly planting that enhance soil function and capture carbon over the long term, are also helping to change things.

For developers and property owners, soil stewardship should be considered not as a regulatory burden, but as a climate opportunity. Every project that conserves or restores soil carbon, makes a measurable contribution to net zero. The cumulative effect across thousands of sites could be significant.  The change in ability to store carbon can be measured. Ruskins achieve on average a 75% increase in carbon storage within 6 months, when caring for soils. 

Another reason soil deserves more attention is its link to biodiversity. Healthy soils teem with life such as bacteria, fungi, insects and small mammals. This underground community plays a direct role in storing carbon. Fungi, for instance, form networks that lock carbon in stable forms. When soil is alive and well, it is far more effective as a carbon sink, it supports all life above it.

This is important because climate policy is increasingly tied to biodiversity targets. In the UK, developers must deliver measurable biodiversity net gain on projects. Currently the BNG targets exclude soils, even though they hold 58% of all the species on the planet according to a recent BBC news item. Managing soils to encourage life is therefore not just good climate practice, but a way of meeting planning requirements. In effect, soil becomes the bridge between carbon targets and ecological obligations.

Measuring the invisible

However, the main challenge for developers is that soil carbon is invisible. Unlike a new solar panel or an electric bus, you cannot point to a soil profile and see the tonnes of carbon stored there. Measurement is complex, involving sampling and laboratory analysis. That makes it harder to incorporate soil into carbon accounting frameworks.

But this is changing. Advances in remote sensing, digital mapping and on-site testing are making it easier to assess soil carbon. Government bodies are funding research to establish baselines and monitoring methods. In time, soil carbon could be traded on markets much like forestry offsets, giving landowners and developers a financial incentive to manage soils responsibly. For now, the business case rests on reputation, regulatory compliance and the wider sustainability message.

However, what is particularly encouraging, is that government policy is slowly catching up. In England, the Environment Act requires biodiversity net gain, without realising this is underpinned by soil health. Flood management strategies increasingly reference soil’s role in water retention, without realising this is also underpinned by healthy soils. As healthy soils drain  upto 10 times better than unhealthy soils, into the ground water and not urban drainage systems. Net zero roadmaps further acknowledge natural carbon sinks, though soils often remain the poor relation to trees and wetlands, as it is not realised it is the health of the soil that governs its ability to store carbon.

For banks and investors, soil carbon is a risk and an opportunity. Poor soil management can lead to erosion, flooding and reduced asset value. Conversely, projects that enhance soil function may become more attractive to funders seeking sustainable investments. If soil carbon accounting matures, it could even become a tradable asset. For now, lenders are watching closely how environmental, social and governance (ESG) criteria evolve.

For us at Ruskins, soil is not a generic substance, but a living material that responds to how it is handled and its health can be improved by decompaction and applying Soil Biology. Getting it right requires expertise in soil science, hydrology and ecology. Unlocking the carbon potential of soil is less about technology than mindset. It requires planners, builders and managers to see soil not as inert ground, but as an active partner in climate goals. This cultural movement is underway, encouraged by policy and demanded by public opinion, but it needs champions in every sector to keep momentum.

All this means that if we are really to achieve net zero, the message is clear - we cannot afford to ignore the carbon beneath our feet. Soil is a giant reservoir, but like any bank account, it can be drawn down recklessly or invested wisely. The choice is ours.