We wipe our feet there, we trample it carelessly, we conquer it, we appropriate it. Some dig it, excavate it, extricate its entrails. Then we abandon it, to bury our waste and other rubbish there. We even end up eating dandelions by the root.
The soil, this unloved, is nevertheless the basis of life on earth. It would even be the hidden face of the living world, the “placenta” of humanity.
It’s not me who says it, it’s Marc-André Selosse, professor at the National Museum of Natural History in Paris and author of a vibrant plea in G major for the preservation of land, entitled The origin of the world.
Selosse is the David Attenborough of the underground world, defender of buried and little-known biodiversity, but so teeming with life that the world could not live without it.
“People don’t care about soil because it’s ordinary, dirty, invisible. We care about the fate of the oceans, because it is magnificent, it is more glamour. People spend their holidays there and have developed an emotional connection. The soils are also threatened, but with general indifference”, maintains this soil sentinel.
True that we are moved for the health of the big blue, but for the fate of the all-brown and its earthworms, the collective momentum is less obvious.
However, the ground is slowly crumbling under our feet, even if the ground holds the key to the rest of the world.
“Soil contains 26% of known species on earth, and 90% of living and dead biomass on earth. It is a cathedral of life that houses micro-organisms, insects, bacteria, viruses essential to plant life and oxygen production, ”explains the defender of this dark world.
A terrestrial microbiota
Like a stomach, the soil constitutes a microbiota essential to the survival of the rest of the planet and living beings, he summarizes. Without soil, there are no plants, no oxygen, no animals, no rivers. Not even fish?
“The ground is the beginning of everything. There would be no rivers without the ability of soils to store water. Soil is a sponge that retains 50 to 400 liters of water per square meter. There would be no fish without the land whose silt will fertilize the most fish-rich coasts of our oceans”, emphasizes the inexhaustible author.
Stuffed with organic matter and Lilliputian fauna, humus-rich soil captures more CO2 released by humans than trees.
However, this composting machine that Selosse describes, this nourishing layer which regulates the rest of life, forms only a thin film around the globe. “You get the impression that the ground is infinite, inexhaustible and very deep. But if you draw a circle on a sheet of paper to draw, the pencil line is actually a thousand times bigger than the actual thickness of the ground,” he says.
The fertile soil, filled with micro-beasts vital to life above ground, is no more than one to five meters thick. A single gram of forest soil is swarming with 100,000 to 1 million bacteria, spores, fungal hyphae, amoebae, earth lice (nicely called springtails), mites and viruses (even SARS -CoV-2!), united in a vast network that extracts and transports essential minerals and foods to the plant and then animal worlds.
under our feet
But this fine film described by Selosse is not immutable. Soils are melting from erosion, compounded by poor farming practices, he says. Intensive plowing multiplies natural erosion by 10 to 100 times, leaving the soil bare, exposed to the action of wind and water, which strips it of part of its oxygen and of a mass of organisms. living. “We don’t understand that we are walking on gold! Something irreplaceable that takes millennia to build. »
One has the impression that the ground is infinite, inexhaustible and very deep. But if you draw a circle on a sheet of paper to draw, the pencil line is actually a thousand times bigger than the actual thickness of the ground.
This brown and wet wealth flies away in the oceans, at the rate of 30 to 40 billion tons of soil each year. Suffice to say that the floor gives way under our feet.
“Around the Mediterranean, we have been plowing for 5000 years. The floors are emptied, skeletons. It’s worse in tropical countries, where a quarter of fertile land is threatened with salinization due to excessive irrigation,” says Selosse.
Under the Roman Empire, the armies used to salt the lands of their enemies to ensure their loss. A lethal weapon that we now inflict on ourselves with fertilizer and irrigation at all costs. “Losing a floor is irreversible,” he says.
Two-thirds of agricultural soils in France are soaked in more than one pesticide and three to four times more heavy metals than forest soil. In China, where the equivalent of the extent of Belgium is too contaminated for any form of cultivation, 20% of agricultural land is contaminated by pollutants.
“A country that destroys its soil destroys itself,” adds Selosse, quoting the words spoken by Roosevelt during the great drought of the 1930s in the United States. We are in an emergency situation. »
giant composter
The myriad of critters that swarm in the ground also suffers from this chemical dusting. However, these underground actors render us irreplaceable services, assures the professor, transforming dead and shit into wonders. “Shit is gold for the floor!” »
Poor soils can no longer produce compost. As proof, in Australia, ruminant dung has become a national problem, for lack of a sufficient number of insects to decompose it. African dung beetles, seasoned with elephant dung, had to be called in to help manage this windfall of droppings.
Even in the cemeteries of Europe there is a new housing crisis: that of the dead who no longer decompose quickly enough to make room for others. Stuffed with antibiotics and drugs used at the end of life, modern bodies are sounding the death knell for bacteria and other agents of decomposition in the soil, observes the author.
The West displays a funny conception of the earth, he says, associated with filth, impurity, latrines, waste piled up there and death.
“We must become aware of its richness, of the importance of protecting it for our food autonomy. Just because we can still grow geraniums doesn’t mean we can feed humanity,” he points out.
We can “rescue” lost soil by reinjecting organic matter into it, says Selosse. “My main fear is: ‘Do we still have time?’ It takes decades. A third of the world’s soil is already degraded, according to the Food and Agriculture Organization of the United Nations, and the war in Ukraine has shown how easily the global food balance can be undermined.
Plain(s) of the St. Lawrence
In the plain of the St. Lawrence, beautiful black soils also fly away in the wind. “We lose two centimeters per year of fertile soil that is one meter long. If nothing is done, these lands will be gone in 60 years. Intensive agriculture undermines the fertility of what we have left,” says Nadine Bachand, analyst at Équiterre, which supports large companies in the southwest in the revitalization of agricultural soils.
The key to life, organic matter, she says, can be reinjected, but bit by bit. Natural grasslands contain up to 7% organic matter, almost five times more than agricultural fields (1.5%). “To bring that up to 3 to 4%, specifies Nadine, it takes 30 to 40 years! »
Only 5% of the territory is zoned agricultural in Quebec, ten times less than in France, she says. In 10 years, the equivalent of 34,000 hectares has been dezoned in favor of highways and other construction projects. “Urban sprawl still continues on the best land. And once concreted, it’s lost forever,” laments Nadine Bachand.
We often say “under the cobblestones, the beach”. A beach, perhaps, but where the broth of underground life is dying. Where there may only be enough left to grow geraniums…