The importance of soil

When walking in the woods, have you ever stopped to consider the importance of the soil beneath your feet? Over 94% of our food comes from the soil, and it provides the habitat for the flora and fauna that form the foundations of terrestrial ecosystems.

Soil is also a significant carbon sink, accounting for 69% of the carbon that is stored in the world’s forests. In a forest, the soil provides the medium in which trees grow and support themselves, a reservoir of water and nutrients to feed them, and a habitat for a wide variety of animals and insects.

Topsoil – an endangered resource

Topsoil forms so slowly that it can be regarded as a finite (limited) resource. It can take around 1000 years to produce three centimetres of topsoil. Globally, topsoil is under serious threat due to modern intensive farming practices such as tilling and using agrochemicals.

We are losing topsoil faster than it can regenerate, threatening future food security. By some estimates, we may run out of topsoil in the next sixty years if we do not make changes to our land-use practices, threatening the livelihoods and lives of billions.

Erosion protection

The good news is that trees and forests have an important role to play in preventing the loss of topsoil through soil erosion. If you have ever noticed dark brown floodwater, you have seen soil erosion in practice. Soil can also be eroded by wind action and when it is damaged by livestock. Trees prevent soil erosion in several ways:

• They intercept rainfall which stops ‘splash erosion’
• They reduce the amount of water in soil through transpiration
• Their roots bind soil to sloping ground
• They break the wind, preventing it from blowing soil away

Many of our new woodlands are planted on land that was formerly farmland and at risk of erosion. As our woodlands grow and the canopies close, the soil will remain protected and begin increasing and improving. Where our woodlands are located adjacent to farmland, they act to reduce erosion and improve soil health and fertility.

Soil creation

In addition to protecting soil, forests and woodlands can also help to create it. This is achieved by two processes; the weathering of parent rock materials (the material from which the soil derives its character, like shale or sandstone), and the decomposition of organic matter. Anyone who has visited a mature woodland will be familiar with the rich organic smell of humus – the dark layer of decaying organic material in a forest.

Soil health and fertility

Trees also help to improve soil health. Their roots improve the ability and capacity of soil to absorb water, reducing the risk of wind erosion. Fallen leaf litter creates new organic matter in the soil, an important element of new topsoil creation. Additionally, the shade created by trees helps to moderate soil temperature.

The importance of trees

Trees do a huge amount for us and for the planet. In addition to creating and protecting soil, trees benefit our physical and mental health, and through carbon sequestration trees help to fight climate change.

We have planted nearly 1.9 million trees so far, and at only 13% towards our goal of creating a 30,000 acre forest we are already the largest new native broadleaf woodland in England. Find out how you can support our work.

References

'Agriculture' by FAO http://www.fao.org/3/u5620e/U5620E05.htm

'Conserving soil: precious, finite and under threat' by the Ecologist https://theecologist.org/2015/aug/05/conserving-soil-precious-finite-and-under-threat

'How Trees Improve Soil Quality' by Rally for Rivers https://isha.sadhguru.org/rally-for-rivers/how-trees-improve-soil-quality/

'Story: Soil erosion and conservation' by Te Ara https://teara.govt.nz/en/soil-erosion-and-conservation/page-7

'What is Topsoil?' by Online Soil https://www.onlinesoil.co.uk/knowledge-base/general-info/what-is-topsoil