Soil for life

David McKay explores the importance of soil for day-to-day life – and how the protection of wild places can have huge implications for overall soil health.

When walking in the hills and exploring Scotland’s wild places, how often do we look down and think about the soil beneath our feet? It can be easy to forget when marvelling at our beautiful landscapes, but soil is critical to all terrestrial life.

It is estimated that half of all species on earth live in the soil. One gram, about a quarter of a tablespoon, can harbour up to 10 billion organisms. Nearly everything that we eat – 95 per cent of food – comes from the soil.

Our soils also perform a huge range of other vital functions, including purifying water, capturing carbon and mitigating flooding and drought.

But why is this important when thinking about protection of wild places? Firstly, soil provides life to all wild plants which in turn provide sustenance for small animals which are then eaten by predators. In this way, soil is an integral part of the food web.

It is also hugely relevant to the ongoing debate around deer management in Scotland. A study by researchers at the University of Edinburgh and Yale University in 2024 calculated annual nutrient losses from the removal of deer carcasses. Using available data on culls in Scotland, scientists estimated that essential nutrients – calcium, nitrogen and phosphorus – are lost in large quantities each year.

This could, the study concluded, have “widespread implications for ecosystem recovery”. The loss of calcium was seen as having the biggest environmental impact, with deer culling stripping the land of more calcium than sheep farming. We know that low calcium levels in soils can impact upon native woodland regeneration and the health of commercial forestry. Meanwhile, nitrogen and phosphorus are the two vital ingredients for plant growth, so any such nutrient losses will have a significant impact.

The John Muir Trust has made the case for leaving deer carcasses on the hill where appropriate. This can mimic what happens in a natural system, where large predators would, after killing and feeding on a deer, leave most of the carcass in situ. This then attracts scavenging animals, insects, bacteria and fungi.

Scientists found that the carcasses are used by a range of vertebrate species, including fox, otter, pine marten and golden eagle, while ravens were the most common. Even species such as mountain hare and red grouse were often recorded feeding close to carcasses.

The ecological significance of carcass removal is clear. Soils benefit from all of those nutrients that are so often being lost, with a knock-on impact in terms of natural ecosystem restoration.

Climate role

Soils also have a key role in tackling climate change – and even more acutely so in Scotland. One of the main differences between Scotland’s soils and elsewhere in the UK is that they contain vast quantities of organic matter – living and dead material from plants and animals.

These organic-rich soils form a significant carbon store – and the more carbon there is in the soil, the less there is in the form of greenhouse gases in the air.

Partly as a result of Scotland’s relatively cold and wet climate, organic material doesn’t break down as quickly as it does in warmer and drier parts of the world, so it builds up in the soil. NatureScot, the Scottish Government’s nature agency, reports that Scotland’s soils contain more than 3,000 megatonnes of carbon – or around 60 times the amount held in the country’s trees and plants.

Peatlands are said to hold the bulk of that carbon store (53 per cent). Such figures have powerful implications for how land is managed in the future – with perhaps a few surprises thrown in.

There is much discussion about the relative merits of various approaches to land management, including rewilding, regenerative farming, peatland restoration, commercial forestry and native woodland regeneration. But when it comes to soils and, in particular, soil carbon, there is uncertainty about the impact of some of these management options often cited in terms of the UK and Scottish ‘net zero’ emissions reduction targets.

For example, a recent academic study cast doubt on assumptions about the carbon benefits of natural regeneration on heather moorland. This followed previous research by scientists from the University of Stirling and The James Hutton Institute that found planting birch and Scots pine trees in heather moorland ecosystems with carbon-rich soils was linked to soil carbon losses that were akin to the amount of carbon captured in the trees. Overall, the study suggested, there may be no net carbon capture in the first few decades following tree planting.

In the latest study, scientists at the Hutton, in collaboration with the University of Edinburgh and Forest Research, focused on natural colonisation of heather moorland, where trees were established from parent trees via seedfall without any human intervention.

After 25 years, the carbon captured in the small, sparsely growing trees did not exceed the carbon lost from the soil, meaning no carbon was captured following the colonisation of these previously unforested ecosystems by trees.

There will be more research done in this space, but it demonstrates again the need to be careful about assumptions on land use change and carbon capture.

Soil health

Of course, there are many other good reasons to plant trees and to encourage natural regeneration of woodland, not least for increased biodiversity and better water infiltration in soils that can help mitigate the risk of flooding. However, depending on the soil type and location, it may not always be guaranteed to deliver on the UK and Scottish governments’ net zero emissions targets.

More broadly, the political focus on climate change and nature restoration has prompted increased interest in the health of soils. We already know that some land management practices erode and degrade soils, and when in poor health, soils lose their ability to support plant growth.

A review published last year by Environmental Standards Scotland demonstrated the scale of the challenge. Degradation of soil takes its toll on the economy, with erosion and compaction estimated to cost £75m per year. Meanwhile, a sum in the region of £16-49m per year is lost due to reduced crop yields from a lack of water retention.

Scotland, which is home to world-leading expertise in soils, adopted a Soils Framework in 2009, which at the time was ahead of the curve. However, this framework was not developed with the intention of being enacted into law, as has been the case in other countries.

In the EU, for example, a proposed Nature Restoration Law includes requirements for setting a satisfactory level for soil carbon stocks and targets for the restoration of peatland soils, while proposals for a Directive on Soil Monitoring and Resilience are also at an advanced stage.

At present, however, no political party in Scotland, or indeed the UK, is proposing such legislation. With a Scottish Parliament election coming up next year, now is perhaps the time to consider whether a new law is needed to offer protection in statute for soils in the same way that we have legal directives for water and air quality.

Whether that happens or not, there is enough reason for us to think much more about the soils underfoot, how they are managed and how best to protect this crucial asset in the face of a changing climate.

About the author

David McKay is Co-Director of Soil Association Scotland, where he leads on research, development and advocacy of the charity’s positions on food, farming and land use. He is also a Trustee of the John Muir Trust.

• This article first appeared in the Spring/Summer 2025 edition of the John Muir Trust Members' Journal. If you would like to receive our Journal twice a year please consider joining the Trust as a Member.