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We take our soil for granted. It is strong, resilient and has been here 'forever'. But is it secure forever?
Should we be paying more attention to the state of soil - perhaps the most important resource we have?
Fragile Earth
Fragile Earth
12million hectares of productive land are lost to desertification each year. New report - drought.
Increasing erosion. So much soil ending up as silt going out to see. All that life washed away
More Flood/Fire events related with climate change also involves soil
We are asking soil to collect more carbon - despite having reducing its content globally, about 60 metric tons of carbon per km2 per year over last 25 years.
Thin Skin
Thin Skin
Our thin layer of soil - that ecstatic skin of earth - is where the interchange between land, life, air and water occurs. All our lives completely depend on that soil surface. Yet it is largely overlooked.
That probably isn't surprising. If the Earth was an apple, only a quarter is land and much of that is pretty barren. Only 1/32 is covered with decent soil, and in the analogy, apple skin would be much thicker than 'topsoil'. Yet, that sliver of skin/soil supports the rest of life!
Apple demo
Cut the apple into quarters. The earth is 1/4 land (25%), the remaining 3/4 is water (75%)
Cut the land quarter in half. One part is mountains, desert or covered in ice 1/8 of total (12.5%)
Cut the other land piece into quarters. Each is 1/32 of the total (3.1%). These areas are too rocky, wet, infertile or covered by buildings and roads
Peel the skin off the remaining 1/32 of the apple (3.1%). The skin reresents the topsoil, which is suitable for growing food crops for the whole world (less than 1%).
Earth
1/4 = Land
Just 1/32 good for growing
'Skin' is thicker than 'topsoil'!
The topsoil layer on Earth, that feeds us all, is much thinner than an apple's skin
🌍 If the earth was represented as an apple 🍏, would the skin be the same thickness as 2 metres of soil?
If we imagine the Earth as an apple, the skin of the apple represents Earth’s crust in this analogy. The Earth’s crust is thin relative to the whole planet—about 30-50 kilometers thick on average for continents and around 5-10 kilometers thick under the oceans.
Earth-as-an-Apple Analogy:
Scale of Earth’s Crust: Earth's diameter is roughly 12,742 kilometers. So, the crust is about 0.4% of Earth’s diameter at most.
Apple Skin Analogy: If an apple is about 8 centimeters (80 millimeters) in diameter, then 0.4% of that would be about 0.3 millimeters—approximately the thickness of an apple’s skin.
Thickness of 2 Meters of Soil
In reality, 2 meters of soil is much thicker than this analogy implies for Earth's crust. If we consider the upper layer of soil specifically, the topsoil layer usually extends only about 10-30 centimeters deep, which is much thinner than even the full apple skin.
In short:
The apple’s skin analogy is closer to representing the Earth’s entire crust, not just the top 2 meters of soil.
2 meters of soil would actually be far thicker than what the apple-skin analogy represents; in this analogy, it's a tiny fraction of Earth's surface layer.
So can I confirm that you are saying the 'topsoil' on earth is much thinner than an apple skin in relation to the apple?
Yes, exactly! The topsoil layer on Earth is indeed much thinner than an apple's skin, in relation to the apple analogy.
To clarify:
An apple's skin (relative to the whole apple) represents the entire Earth's crust in this analogy.
The topsoil (the rich, organic layer we often associate with plant growth) on Earth is only a fraction of the Earth's crust. This topsoil layer is usually only about 10–30 centimetres deep, which is much thinner than the apple skin would be in relation to an apple.
So, in this analogy:
Topsoil is far thinner than the skin of an apple.
Earth's crust as a whole is more similar in thickness to the apple's skin.
Losing Soil
Losing Soil
Soil processes have not always been here. This site is dedicated to telling the story of how soil got here. Together processes built the structures, the crucial aggregates, with an architecture of their own, to house quadrillions of moving creatures. When we wreck that structure, much of the life goes with it. Yet we do not seem to notice, even when our rivers silt up with what was once soil. The Romans didn't ask why the Tiber silted up, nor do we when 2-3 million tons is lost from the UK to the sea every year. There are few personal or political campaigns about soil losses over the world. Yet that soil represents millions - hundreds of millions of years of life- to get here, now lost forever.
Roman silting
The Tiber River in Rome silted up during the Roman period:
Sedimentation
The Tiber River's east bank accumulated layers of silt, which caused the river to shift westward. The siltation was likely due to a combination of the river's erosive power and the depositional forces of the river and its tributaries.
Flooding
The Roman period saw increased flooding of the Tiber River, which covered the lower parts of the city and backed up sewers.
Harbours and ports
The siltation and flooding caused harbours and ports to need to be moved, which was a burden on the economy.
Silted basin
The basin of the first harbor of ancient Rome was silted.
The Tiber River was a vital source of freshwater and rich soil for Rome, and was also important for trade and commerce. Ships could travel up to 60 miles upriver, and the river was used to transport grain, stone, timber, and food to Rome.
From that thin skin, we are loosing soil to
Anthropocene
Anthropocene
Officially, the current epoch is called the Holocene, which began 11,700 years ago after the last major ice age. “The Anthropocene Epoch is an unofficial unit of geologic time, used to describe the most recent period in Earth’s history when human activity started to have a significant impact on the planet’s climate and ecosystems. The word Anthropocene is derived from the Greek words anthropo, for “man,” and cene for “new,” coined and made popular by biologist Eugene Stormer and chemist Paul Crutzen in 2000…"
I think it appropriate that the ‘mushroom cloud’ that signalled the end of World War 2 starts this epoch.
The word Anthropocene
The word ‘Anthropocene' was coined in 2000 emphasizing anthropogenic changes in climate and geochemistry of the Earth system[2] But now it simply refers to the modern era of human domination of the Earth. Some choose to use the word others don’t. I choose to use the word ‘Anthropocene’ to highlight the dramatic changes going on, mainly caused by human intervention. This has never happened before on this scale, but whether it is a new Age will be decided long after I have joined this earth. That is up to you to decide.
The two main 'Anthropocene debates' are when it started - some say it is the industrial revolution others after World War 2. And whether what is happening is part of 'normal' evolution or heralds extinction
Evolution or Extinction?
Are our soils continuing to evolve, or are they heading for extinction?
Some are saying that we are now on our Sixth Extinction "Although considerable evidence indicates that there is a biodiversity crisis of increasing extinctions and plummeting abundances, some do not accept that this amounts to a Sixth Mass Extinction".(Cowie & Bouchet 2022)
Part of this debate is about whether matters are part of a natural cycle or the start of the latest ‘extinction’.
“The primary question that the IUGS (International Union of Geological Sciences) needs to answer before declaring the Anthropocene an epoch is if humans have changed the Earth system to the point that it is reflected in the rock strata”
But even that is not straight forward. In the book ‘Theory of the Earth, Thomas Nail explains. “Geological time used to refer to slow and gradual processes, but today we are watching land sink into the sea and forests transform into deserts. We can even see the creation of new geological strata made of plastic, chicken bones, and other waste that could remain in the fossil record for millennia or longer. “
Soil Survival
Soil Survival
Of the previous 5 extinctions, soil would not have been around in Ordovician-Silurian Extinction (440 mya). Living fossils, - ie plants and animals that look the same today - have been found before the Devonian Extinction (365 mya). Soil, with lichens, probably paid a major role restoring life after the great Permian-Triassic Extinction (250mya) and continued to flourish following Triassic-Jurassic Extinction (210may). Soil helped provide the dinosaurs' relatives - birds - with feeding matter (worms & ground beetles) after Cretaceous-Tertiary Extinction (65 mya). What would be soil's role if we are moving to a sixth extinction?
Big questions
Big questions
Are we treating soil differently from previous civilisations? What has happened to our soils since the second war?
What are the long term impacts of the massive increase in mechanisation along with more artificial fertilisers and many clever chemicals to kill any 'unwanted' life. There have been many changes, but two massive movements affecting soil, since the war, are the Green Revolution and Globalisation. Then there is all that concrete and tarmac which covers the soil. What do these combined impacts have on the present state of soil?
How do those soil changes affect what we is happening to our planet? There are massive and important questions that we need to examine more closely. We are beginning to look more at the dynamic between what we are doing to soil practices and how soil reacts with the rest of the world, particularly in terms of warming.
There is a new science developing called the quantification of soil genesis. (Stockmann et al 2014). This is because there is increasing concern soil may be degrading faster than it can be replenished. This science examines whether we are reaching ‘peak soil’. This is the state where the world soils are not sufficient to sustain their ‘fertility’, and are degrading faster than they can be replaced.
New ways of seeing soil
New ways of seeing soil
Soil, with its dynamic exchange between land, life air and water, is a crucial aspect of global warming. This is not just for carbon exchange, but direct heat exchange too. There is a vital reciprocal link between climate changes and the state of soils. As they are being explored, we are finding out more about the soil, from different ways of seeing.
In recent years we have heard how soil can help ‘sequestrate’ carbon, meaning holding on to it rather than burning it off as carbon dioxide and methane into air. There is more carbon in the soil than all the life and air above ground. But soil is not a lump of carbon (despite some areas like coal, oil and shale) but a living entity. Carbon in soil is predominantly attached to nitrogen, oxygen hydrogen and many other elements to make the molecules that run life. We need to see soil as organic matter - life- rather than a lump of carbon.
"Root inputs are approximately five times more likely than an equivalent mass of aboveground litter to be stabilised as Soil Organic Matter" (Laitha et al 2017)
We need to learn a lot from what is going on now in order to work out what we can do in the future to 'Save our Soil!'.
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