Before you start reading this story, can you answer the question: “When did the soil evolve?" I asked this to 'Sense about Science' Soil - a non renewable resource. But didn't really get an answer.
Does this question sound strange – or does it make sense to you? It probably makes more sense if you consider the soil is a 'living entity'. This 'entity' is somewhere between an organism and an ecosystem. But if it is living, when was it born? It must have been some date, as it was not always there. And yet now we call ourselves 'The Earth'. There were always rocks, but not always soil. I presume you consider it is more than 7 days or 4000 years ago, but is it one million years ago, ten million, 100, million, 200 mya, 400 mya or even further back – perhaps in Pre-Cambrian?
As a start check out BBC clip of Deep Down & Dirty. This starts to bring the soil to life, which is seen mainly as 'worms and fungi'. Yet there is so much more in the soil food web, particularly the little arthropods - the 'meso' fauna..much smaller than worms, but but visible as a speck. in terms of total biomass in the soil, mesofauna are much less than worms, but are doing more of the job of moving carbon around (see CEH research). There are probably 500-1000 individual mesofauna for one worm. Each interacting in ways that still need to be explored.
These soil inhabitants give a clue to a possible answer that question about soil origins. The main families of organisms are remarkably consistent throughout the world. Does that help us determine the date?
When did our soil evolve?
Many people might think that an odd question. We don’t hear many people discussing when and how the body called ‘soil’ evolved. Yet it must have. If the soil is ‘living’ then it must have evolved alongside all of the other organisms. Yet it fails to get a mention. It is as if it has always been just there. Under our feet. But it hasn’t. The first life was probably in water or sediment, which is a long way from the composite, friable, clod of life we know today as ‘soil’. Yet, we would not be where we are today without it. We talk about the evolution of plants and animals, but rarely hear about the evolution of soil. Yet it is the same the world over – which tells us something.
We refer to the soil as ‘the living soil’, made famous by the self titled book by Lady Eve Balfour. We keep forgetting it is alive and a whole complicated ecosystem exists of countless relations not just between the fungi and worms, a popular perception. All the 100s of species mesofauna – small but quite minute creatures consisting mainly of mites, springtails, nematodes, live alongside the massive earthworms. There are many species, eating spores, roots, other creatures and providing the massive surface areas for the microflora to work on.
The vital part of the soil – which literally binds the world together, is only about an inch thick. It should not be seen as just a receptacle for chemical inputs. Soil is not just a physical or chemical entity but a biological ecosystem. An ecosystem that is capable of transforming rock into complex organisms within 50-100,000 years. There have been places and times when the fragile structures have broken down leading to dust bowls. Without it, quite simply, we along with many other creatures, are dead. Plants tend to be seen as an addition to the soil, yet it looks more likely that they developed relationships with soil animals - springtails and mites, integral to the evolution of soil.
These animals are not just an after-thought thrown in after the usual physical explanation for the development of soils where plants and later animals are thrown into the equation with no real analysis of how those biological entities transform the physical and chemical organisation. What is their role? We make guesses based on the animal appearance eg we can make out that some mites are predators not herbivores, by the shape of their mandibles, but we don’t know what they eat. (ref new Odum publication). Darwin taught us about how earthworms munch and crunch their way through. We now need somebody to explain the role of all these other creatures in creating the fragile living soil structure, and how these co-evolved and now co-exist.
So if this is living – perhaps not an organism, but certainly something like gaia predicts, And talking of Gaia, the Gaia man – James Lovelock said (at Hay Festival) that the trouble with all the climate change models is that they are only physico-chemical, that the living components are not yet computed in. We need to add the ‘biological’ into those algorithms, and the soil biology will be the biggest input.
So when do you think the soil evolved/appeared?
In the beginning was the Big Bang
And, among the trillions of suns created,
In an obscure galaxy, called the Milky Way
A planet flew from a sun about 4.5 billion years ago
Consisting of rock and water,
Later sand, silt, n sludge.
Life appeared within a billion years, starting as cells in sludge
The simple animals/plants about a billion years ago
and, sometime after that the living soil evolved
All over the world
With the main animal inhabitants springtails, mites nematodes and earthworms
They were in the land before insects arrived
They created the soil food web, along with the fungi and bacteria.
It is this soil that gives the planet its name - Earth.
And which enabled all those 'Higher' plants and animals to appear
That we now wonder at and call 'Nature'.
Yet we treat this soil like dirt.