Earth story

Soils are critical to the health of our planet and essential for human, animal and plant life. They provide the nutrients and water required to grow food; they also support biodiversity and help to regulate climate, floods and droughts. However, soils – and the many varied benefits they provide to humans and wildlife – are at risk from changes in climate and land use.

A recent report by the EU’s Mission Board for Soil Health and Food estimates that 60-70% of soils in member states are unhealthy, and has set a target of 75% healthy soils by 2030. While we still have much to learn about soils, NERC-funded research – through monitoring, experiments and modelling – over many years has provided significant understanding of their functions and the way they mitigate climate change.

Tractor plowing field

Working with key research  institutes, such as the UK Centre for Ecology & Hydrology (UKCEH), and by supporting leading soil scientists, NERC is not only helping to further global soil science, it is also generating evidence that informs policy.

In the wake of growing scientific evidence, the Department of Environment, Food and Rural Affairs (Defra) has announced that soils will be a cornerstone of its Agriculture Bill, which is set to introduce a new system of farming subsidies to replace the Common Agricultural Policy (CAP) in England, following the UK’s departure from the EU. Wales has already enshrined soil carbon protection in law; and Scottish planning policy also recognises soil as a physical asset and highlights the need to maintain and improve its condition.

In England, the legislation pledges to reward farmers and land managers for schemes that improve air and water quality, soil health, animal welfare, public access to the countryside or reduce flooding. The Government’s aim is to boost farmers’ productivity and protect the environment, including supporting its commitment to reach net zero emissions by 2050.

The Welsh government’s Sustainable Farm Scheme will pay for environmental outcomes whilst providing stable income for farmers. Plans for CAP replacement are still under development in Scotland and Northern Ireland.

Professor Bridget Emmett, Head of Soils and Land Use at UKCEH, and a member of the EU mission board, says: “Our research into soil health, emissions, biodiversity and productivity will provide the data and insights that the UK’s national governments need to develop a new system of paying farmers and other land managers for environmental benefits, while supporting our farming and forestry industries to ensure we don’t export our emissions and impacts to other countries.”

Climate regulators

Soils are crucial to any plans to reduce overall greenhouse gas emissions; they store huge amounts of carbon – an estimated 1,500 billion tonnes worldwide, which is more than in the atmosphere and vegetation combined.

Healthy soils can mitigate climate change. This could be directly, by ‘locking in’ and keeping soil carbon that would otherwise be released into the atmosphere as CO2 or methane, or indirectly, by supporting the growth of plants, which remove CO2 from the atmosphere via photosynthesis.

Conversely, certain land management practices such as drainage for agriculture and forestry use, inefficient application of fertiliser, over-tillage and livestock grazing can exacerbate soil degradation, causing the extensive release of soil carbon and limit plant growth. This leads to negative impacts on the ecological food chain and the amount of CO2 captured from the atmosphere.

As part of efforts to tackle the problem, the LOCKED UP project – led by UKCEH and backed by a grant of £1.8 million from NERC – is enabling scientists to better understand the processes of soil carbon formation, stabilisation and loss. The multidisciplinary project will help quantify the amount by which we can increase soil carbon storage to mitigate climate change.

UKCEH’s Dr Jeanette Whitaker, who is leading the project, says: “For the UK, the focus needs to be on reversing losses of soil carbon in cropland and peatland soils. This will improve soil health and resilience, which in turn will support future generations of farmers and foresters, as well as support the rich biodiversity of soil. It will also contribute to climate change mitigation.”

Vicious circle

Another NERC-funded research project, at a long-term soil experimental facility in Clocaenog, North Wales, led by UKCEH, has found that soils are themselves affected by changes in rainfall patterns and higher temperatures caused by climate and land use changes.

When soils are very wet, as is the case for upland soils during many parts of the year, they release less carbon because soil organisms are less active and plant material decomposes very slowly. However, when soils dry out, soil activity and decomposition speed up, leading to an increase in the release of carbon.

Dr Sabine Reinsch, a soil ecologist at UKCEH, says: “Global warming causes more frequent dry spells, so the soil's ability to keep its carbon is reduced, resulting in a greater amount of CO2 being released into the atmosphere. This, in turn, contributes to increased warming and more frequent droughts, thereby further increasing the amount of CO2 released into the atmosphere by soils. It is a vicious circle.”

Studying the soil

For the past 20 years, scientists from UKCEH have been carrying out experiments at Clocaenog to assess soils’ response to global warming and drought. Receiving a much higher annual rainfall than average, the area’s ecosystem is dominated by heather, moss and lichen, and it holds a large pool of soil carbon.

Experimental plots are designed to reduce the amount of rainfall reaching the vegetation and the soil, and to increase the air temperature. Researchers found that in plots mimicking future drought conditions, the soil lost up to 10% of stored carbon back into the atmosphere.

Research at Clocaenog, which is part of European climate change manipulation network, INCREASE, has resulted in more than 60 scientific publications to date. Professor Bridget Emmett says: “Long-term monitoring sites such as Clocaenog are essential to furthering our understanding of the long-term impacts of climate change on plants and soils.”

With soil health at centre-stage of governments’ plans to support sustainable land management, continued investment in soil science will help to secure a sustainable and prosperous future for the UK.

Digging the dirt

  • Soils provide a home to a quarter of the species on Earth.
  • Soil is made up of organic matter, minerals, air, water and a variety of organisms including plants, invertebrates and microbes. The organic matter is derived from the decomposition of these organisms, while the minerals are particles from large rocks that have been broken down by physical, chemical and biological processes over a long period of time.
  • About one-third of the world’s soils have been degraded throughout human history, adding almost 500 billion tonnes of CO2 to the atmosphere.
  • Soils are crucial to mitigating climate change. Plants channel CO2 from the air to soils and consume about one-third of the CO2 that humans produce. Of that, about 10-15% ends up in the soil.