On the Soils of Our Feet - A Celebration of the Dirt Beneath Us

by Sinéad McMahon

Not exactly the sexiest day in the United Nations calendar, December 5th marks World Soil Day (WSD), created in 2002 to help recognise the importance of healthy soil and focus international attention on sustainable management of soil resources. Less glamorous than its counterparts, such as World Turtle Day, soil is often overlooked and underrated, but each year brings soil the growing hype and recognition it deserves. Last year media coverage of WSD reached 653 million users worldwide, with social media playing an important platform in raising awareness. Many governments are becoming increasingly aware of the importance of their soil resources and shaping strategies accordingly, with 140 nations currently contributing to the success of WSD, we are finally starting to appreciate the underdog that all terrestrial life depends on – soil.


We all know what soil is, but what actually is soil? When asked, it’s hard to put into words this ‘thing’ that we are all so familiar with. Soil is created by a slow physical, chemical and biological weathering of bed rock, a thin layer of material covering the surface of the earth also containing minerals, water, air, organic matter and living organisms. It can take up to tens of thousands of years for soil to form, depending on factors such as weather conditions and rock type, making it a non-renewable resource on a human time scale. So then what’s the difference between soil and dirt? Well, dirt is soil that has been moved from where it occurs naturally, removed from its own ecosystem; dirt is soil that is in the wrong place. We get dirt on our hands when we do the gardening, our boots are caked in dirt after a long walk in the woods where we then traipse dirt through the house after the kitchen floor has just been mopped, but the soil is what we leave behind.


~ “Soil is the earth’s fragile skin that anchors all life on earth.” WWF ~


One gram of soil contains at least 1,000 bacterial species and it’s believed that we are yet to discover the majority of species living in our soils. Soil plays a fundamental role in providing habitat, shelter, water, air food and nesting grounds for a big community of diverse organisms across the globe. Earthworms eat their way through the soil, absorbing nutrients and energy and playing an important part in mixing and aggregating the soil, loosening compact soil and mixing organic matter. Astoundingly 15 tonnes of soil can pass through one earthworm each year! But not all organisms that are found in soil spend their entire life cycle beneath the surface, some species only use soil as a nesting ground. A female Komodo dragon (Varanus komodoensis) will excavate soil to around 2.5m deep before laying her eggs, then, depending on the soil temperature and moisture, the eggs can take anywhere between 2.5-8 months to incubate. Hatchlings begin their life by climbing up through the soil, emerging in search of a suitable tree to climb to seek safety from predators.

Komodo dragon resting on soil on the Komodo Islands, the same soil that the dragon would have dug up through at the very start of its life


There are several reasons to celebrate soil, the list is extensive so let’s wrap it up with a few key ways in which soil contributes to our modern society:


  • Soil stores water, this is particularly important for flood management as healthy soil can hold up to 9200 tonnes of water per acre, greatly reducing flood risk, this equates to about 0.01% of all water on earth being stored in soil. This fundamental feature sustains the life on our planet by providing water to all living organisms in the soil; rising global temperatures, wind and extreme weather events can all negatively affect the moisture levels in soil with the potential for soil erosion.


  • Almost all the antibiotics we take to help fight infection were obtained from soil microbes; soil bacteria and fungi can both be used to develop antibiotics, for example penicillin which came from the Penicillium fungus found in soil. As a result, antibiotics have had a major impact on increasing human life expectancy making soil a vital contributor to human well being in more ways than one.


  • Without soil we would have no infrastructure, soil contributes directly to building materials such as bricks and cement and provides physical support to stabilise buildings and structures, from bridges to skyscrapers, roads to stadiums, none of our infrastructure would exist without soil. Engineers must test soil at sites before construction can begin; soil can make or break building projects.


  • There’s no denying that soil is fundamental in the provision of food, fuel and fibre. Astoundingly 2.16 million citizens of the United States work the soil every single day, with soils supporting 95% of all food production worldwide. Even our clothing is derived from the soil, the garments we wear grow from plants that are supported by soil ecosystems.


  • Soil holds all the secrets to our heritage and history. Thanks to archaeology we can uncover artifacts in the soil that help us unlock knowledge of past civilisations, with fossils teaching us about the natural history of our planet.


~ “The nation that destroys its soil, destroys itself.” Franklin Delano Roosevelt ~


It may not come as a surprise that modern agricultural practices play a large role in soil degradation (the decline in soil condition caused by its improper use or poor management), we have been over-using our land and contaminating it with many by-products. Soils are becoming severely damaged by intensive farm practices, as the layer of fertile topsoil thins it becomes increasingly difficult to grow crops. Although to the eye it may not seem like we have a shortage of dirt on the planet, it’s the quality of the soil that matters. Compaction, acidification, contamination, increase in salinity, erosion, nutrient imbalance, water logging and loss of soil biodiversity are just some of the ways in which soil is being negatively affected across the globe.


The dry soil of a potato farm in South Australia where the climate is hot and dry throughout most of the year


Did you know that soil can die? And in the past 150 years we’ve lost half of the planets topsoil, the building block that makes soil productive. Not managing our soil resources can lead to dire consequences, one prime example of this is the American dust bowl of the 1930s where poor land management led to the displacement of 500,000 American citizens. Over many years agricultural crops replaced deep-rooted native grasses destroying 100 million acres of once-fertile grassland, killing the living networks that held the soil in place and kept the soil moist. After a severe drought the ‘Dust Bowl’ brought a series of severe dust storms and the resulting wind erosion lifted away more than 75% of the topsoil in many areas of the Southern Plains, resulting in failed crops across the entire region.


~ “Each soil has its own history. Like a river, a mountain, a forest, or any natural thing,

its present condition is due to the influences of many things and events of the past.”

Charles Kellogg, The Soils That Support Us, 1956 ~


Just like our oceans, soils store a large proportion of the worlds carbon, with approximately 75 billion tons of carbon stored in European soils alone. As part of the process of photosynthesis, plants pull carbon in from the atmosphere and turn it in to carbohydrates (sugars), some of those sugars get pumped down through the roots to feed microorganisms that build soil. In a nutshell: plants pull the carbon in and the soil stores it. So it’s thanks to soil that 25% of the worlds fossil fuel emissions each year are removed from the atmosphere, most of which is stored as permafrost and peat in northern Eurasia and arctic areas, as soils in hot or dry areas store less carbon.


There has been a lot of debate in recent years about whether it is better to have a real or artificial Christmas tree, weighing up the impacts of deforestation against plastic production; a real tree that is grown with care seems to be the most sustainable choice. If you decide to purchase a real tree this Christmas look out for a Forest Stewardship Council certified tree to ensure that the tree you purchase is grown with consideration for our soils. When you’ve finished with your Christmas tree be sure to compost it to be used as a soil improver or contact your local authority to see if they will collect your tree for chipping, the chips are then used for mulching which will further improve soil health.


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