Dr Helaina Black: Improving soil could mean pay dirt in the battle against climate change

Dr Helaina Black leads the Ecological Sciences group at the James Hutton Institute

Although this may not seem like a major change, it is enough to mean that we have fewer frost days (the last frosts are earlier in spring and first frosts are later in autumn).

It also means a greater intensity of more unpredictable rainfall with an increase of more than 50 per cent in the west, and rising sea levels – nearly a 60 mm increase in sea level at Aberdeen. The climate changes are also reflected in longer growing seasons for both wild plants and crops.

But did you know that this is also affecting our soils? Most noticeably, the periods when soils have too little water to sustain plant growth, known as soil moisture deficit, are happening more frequently and for longer periods in a growing season.

When it does rain, it is often more intense and more of it, potentially leading to more and faster runoff. For farmers, this means a greater reliance on irrigation, looking to grow crops that are more suitable for drought conditions and using management practices that will help keep water in the soil.

At the same time, it means working to protect the soil from erosion and speeding up the movement of water into soil, as opposed to over it; this helps to keep soil in the field thus reducing the movement of sediment to rivers and helps limit down-stream flooding. At the James Hutton Institute, we are trialling a wide variety of options to help adapt soils to climate change.

For example, we are trialling diverse cover crops and novel tillage methods which help to bind the soil, maintain soil structure and provide more routes for water to enter and to retain soil organic matter which is essential for a healthy soil. In parallel, we are working to provide practical information on the soils at most risk from erosion.

We are all being encouraged to reduce the amount of carbon dioxide and other greenhouse gases entering the Earth’s atmosphere and so limit severe impacts of global climate change. Scotland’s soils can be part of this global effort.

The amount of carbon in Scotland’s agricultural topsoil is 3000 times more than the carbon in all the trees in Scotland. Our research has indicated that there is an opportunity to increase carbon storage in cultivated soils by adopting management that adds organic matter to the soil together with management to retain organic matter in it.

We already know a great deal about these management options and our research is helping to identify options that benefit the soil while helping to maintain productivity.

For example, legume cropping can increase soil organic matter. Legumes are an excellent source of protein, but they are not widely grown across Europe.

Our EU-funded TRUE project is coordinating 24 partners across Europe to explore the best ‘transition paths’ to increase sustainable legume cultivation and consumption, which would benefit soils and climate change mitigation. Increasing soil carbon as organic matter has other benefits further helping to reduce the impacts of climate change – and water is an excellent example here.

Scotland’s cultivated soils can currently hold about 3,274 billion litres of water, the equivalent of 1,300 million Olympic-sized swimming pools, for growing crops. By increasing their carbon content, this would greatly increase the water storage capacity of Scottish soils.

This additional capacity could not only help reduce the risks of soil erosion and drought but also help to reduce flood risks by slowing down water moving through the landscape to streams and rivers.

Increasing organic matter can also increase the abundance of diversity of soil animals such as earthworms, which further improve the soil structure and provide more food for much threatened farmland birds and wildlife. So it’s a win-win situation on top of helping combat climate change.

As recently highlighted in the press, there is only a small window of opportunity to act before changes in the global climate will have ongoing severe impacts on people’s health and wellbeing.

Scotland has a clear opportunity with cultivated soils to contribute to slowing down climate change. We all need to work fast to ensure that this contribution can make a difference globally, not only locally.

Dr Helaina Black leads the Ecological Sciences group at the James Hutton Institute and wrote this article with colleagues Allan Lilly, Mike Rivington and Jagadeesh Yeluripati to highlight World Soil Day, held annually on 5 December to focus attention on the importance of healthy soil and sustainable management of soil resources. For more information visit www.hutton.ac.uk