« The soil is the main resource of humanity and requires a global policy of safeguarding. Soil resources are limited and constitute only a thin and fragile surface layer of the earth’s crust, extremely vulnerable to overexploitation and mismanagement. All terrestrial ecosystems are dependent on soil; without it, the plants that provide us with food, fiber, fuel, lumber, and oxygen could not grow. »(1)
Life is rare in the universe. And all the efforts born from the hope to find traces of it elsewhere than on our planet remained to date vain. On the surface of this one, from where we observe it, the life seems to be omnipresent. It is reborn from all extinctions, adapts to the most extreme conditions and presents itself in such varied forms that it gives the illusion of being the norm. However, our biosphere is quite thin compared to the twelve thousand kilometers of diameter of our planet. Thirty meters below the earth’s surface, there is no life — or almost no life — left, and our atmosphere is only a few kilometers thick. In fact, most of the earth’s biomass and biodiversity is concentrated in a thin layer of fifty centimeters thick on average worldwide: the soil. Our planet, whose oceans and atmosphere are much larger than it, was rightfully named Earth. It is indeed the only planet to have a soil, in the pedological sense, i.e. not an inert support, but a living organo-mineral medium.
Soil is the surface layer of varying thickness of continental surfaces that results from the alteration of bedrock under the action of climate and living organisms. It is both the product and the support for the development of vegetation, and therefore of the continental biosphere. As an interface with the atmosphere, water and rocks, it plays a central role in the regulation of the major planetary cycles such as those of water, carbon and nitrogen. Thus, the soil, which is the real hub of terrestrial ecosystems, is at the heart of major global issues such as food security, climate change and biodiversity. Yet it remains largely unknown and often considered as a simple support for our cultures and infrastructures. Reconsidering the soil, an exclusively terrestrial environment, full of life but particularly fragile, is therefore an essential necessity.
The whole process that leads to the formation of a soil, pedogenesis, is a slow phenomenon. Depending on the climatic conditions, it takes from a thousand to several tens of thousands of years for a soil to form.
The first constituent material of the soil is the bedrock. Once exposed, and when conditions permit, it is colonized by pioneer species (bacteria, algae, lichens, mosses). It is their biological activity and the contribution of organic matter that they represent that allows the process of soil formation to begin. These pioneer species chemically attack the rock, and leave a substrate that can accommodate other species. This is the beginning of a long cycle of ecological successions during which the living communities will become more and more complex and the number of species will increase, until a state of stability called climax. During this process, the soil thickens by the alteration of the bedrock at depth, and by the accumulation of organic matter at the surface. It progressively forms an environment that can be colonized by the roots of the so-called higher plants, up to the trees. It becomes the habitat of an extraordinary multitude of organisms that work and stir it constantly. During this maturation of the soil, different strata called horizons are differentiated according to their composition. The more advanced the soil, the more distinct these horizons are. Since the end of the last ice age, about twelve thousand years ago, the diversified deciduous forest has gradually replaced the tundra in Europe. It is indeed the climatic vegetation of the soil-plant system in our latitudes. Without the influence of man, the European territory would be mostly covered by forest today. The climactic state is the most stable and resilient state of a system and the one towards which it tends spontaneously.
Consequently, the primary cause of land degradation in the world is deforestation. Our ever-increasing need for wood as energy and raw material, as well as for land for cultivation or construction, has resulted in the destruction of almost all primary forests in Europe and is currently exerting ever-increasing pressure on the last large natural forests.
Inappropriate agricultural practices and urbanization are the other two major causes of soil degradation. In ten thousand years of agriculture, man has destroyed two billion hectares of agricultural land. Half of them in the last century. Regarding the artificialization of soils in France, the largest agricultural producer in the European Union, Jean-Marc Jancovici explains that with « Assuming the continuation of trends, it takes a little more than a century and a half to build up 100% of the territory, or more precisely, the current growth in built-up areas leaves us with 160 years of land consumption, assuming, of course, that we are able to do without agricultural land, forests, and a few other little trinkets. If we assume that we cannot do without a large 50% of the land for agriculture and forestry, then it only takes a century to urbanize the remaining 50% at the current rate. »(2)
The soils we inherit are the result of a long process of aggradation under vegetation little or not disturbed by man. The suppression of this one is the first stage of a process of degradation which can have for consequence, in the most extreme cases, the desertification. The Executive Secretary of the United Nations Convention to Combat Desertification, Luc Gnacadja, warns us: « At the current rate of land degradation, water and food needs will soon no longer be met. Only by preventing this degradation can we face the challenges of climate change, population growth, poverty reduction and food security ».(3) He points out that 12 million hectares of productive land are lost every year.
If we are concerned about the degradation of the three environments where life flourishes — water, air and soil — this one, because of its unique organo-mineral composition, deserves special attention. Indeed, water and air gases are composed of molecules. These are formed by atoms linked together by atomic bonds. This makes them extremely strong environments. We pollute them by releasing toxic products or by unbalancing their composition, but we cannot destroy them.
The soil, on the other hand, is the result of a synergy between clays from the parent rock and humus from organic debris. These particles are electronegative and naturally repel each other. But ions (calcium, iron, aluminum, magnesium) attach them to form the clay-humus complex. These fasteners are electrical, i.e. chemically weak. The clay-humus complex plays an essential role in the stability and structure of the soil, which, unlike water or air, is a particularly fragile and destructible medium. A degraded soil exposed to the harshness of the climate will break down: it will erode and disappear.
Thus, if the causes of soil destruction are multiple, the destruction process is always the same. It starts with biological degradation, which leads to chemical depletion, and ends with its physical destruction.
As we said, healthy soil is teeming with life. Each species, by its particular behavior, participates in its proper functioning. In this respect, the large earthworms, known as anechoic worms, are a key species. They are to soil fertility what bees are to the pollination of flowering plants. They can be found from one to four tons per hectare, (but down to less than a hundred kilos in soil bludgeoned by plant protection products and heavy cultivation techniques such as plowing) and they eat their weight in soil per day. They are the ones that continuously mix the clay-rich deep soil with the humus-rich surface soil and bring up the elements carried by the water to the water table through their dejecta. It has been shown that the passage of soil through their gut promotes the formation of the clay-humus complex. Without the biological activity that counteracts the physical laws, the soil leaches and becomes chemically impoverished.
When the chemical degradation becomes too important and the cations that allow the binding of clays and humus are also leached, the clay-humus complex can no longer be formed.
The soil then loses its stability. Water and wind erosion carries away the finest particles, until the bedrock is uncovered in extreme cases, and leads to desertification in arid areas. Often considered as one of the main causes of soil degradation, erosion is above all the consequence of an important biological and chemical degradation, although not very visible.
Although the fundamental role of soil life is beginning to be recognized and mentalities and practices are beginning to change, soils have long been and are still often considered as inert and exploitable supports. Yet they are home to 80% of the world’s biomass. Their biodiversity, essentially microscopic but much greater than that of the surface, is estimated at one hundred thousand to one million different species per gram of soil for a total population of up to ten billion individuals!(4) We have said that the total weight of earthworms alone is greater than that of all other animals combined. The roots of plants, which are generally much larger in volume than the aerial parts, can represent a network of four billion km per hectare(5)and the underground filaments of the mushrooms constitute a kind of net of ten thousand kilometers per square meter, which can live several thousand years. As many bacteria, algae, mollusks, arachnids and myriads of insects, to name but a few, share all the horizons. All these organisms weave complex relationships between them that are still poorly understood. Each one plays its role within this immense and complex group of living beings whose intense activity, totally free and silent, ensures the proper functioning of the soil. Note that our climatic forest is much more productive than our agricultural systems, and this without fertilizer, pesticides or ploughing.
Of course, if the soil-plant system finds its climatic equilibrium under forest vegetation, we do not eat wood, build our houses or supermarkets in trees, and we must act on our environment to live. So it might seem legitimate to consider soil degradation as a necessary evil that allows us to feed, house, heat, etc. But if man has always modified his environment, as do all other species, the powerful tools he has recently acquired to serve his ever-growing appetite for development make this initial struggle for life a veritable enterprise of destruction. A real « war on life »(6) which, in fine, could well turn against its biped and conscious protagonist by transforming to such an extent its living conditions that its capacity of adaptation is not enough.
Such a state of affairs should not fail to make us question the so-called rationality of the economic thinking that underlies the worldview that is supposed to be imposed on us, under the pretext of its objective and almost natural necessity. In a book that remains a reference today(7), François Terrasson exposes his main thesis: the real cause of the destruction of Nature, understood as that which exists outside of any action on the part of man, is a deep and largely unconscious fear of it. It goes without saying that the ground, an obscure and mysterious environment par excellence, which its own dynamics constantly covers with untidy wasteland and dark forests, is a fertile ground for our unconscious fears. We prefer to sterilize it, cover it with concrete. This tangle of roots, brambles and dead things, populated with carapaces, swarming with larvae, mandibles, and creatures that are so dissimilar to us, is also the place of the Underworld in Greek mythology. And then the earth is dirty. It is covered with all kinds of excrement and, worse, it is where our dead are decomposing. Who still regularly puts their hands in the ground? Not the urban population, which has recently become the majority in the world, and less and less the farmers, who plough their subsidized hectares from the top of their air-conditioned tractors. Our culture has made us sensitively out of touch.
Yet the earth is our cradle and our grave. It is from her that, in many traditions, God creates the first man. Many soil conservation techniques exist, particularly in agriculture, which could be developed and more widely applied. Organic farming, biodynamic farming, agro-ecology, use methods that limit the use of pesticides, chemical fertilizers, or heavy work on the soil, and preserve its life. They must be improved and generalized. But the main obstacle to soil preservation is probably not technical.
We must learn to consider with humility this humus from which humanity is born. We must learn to love the earth not only for what it gives us, but for what it is. We must learn to see the earth no longer as a dirty, unmodern thing from which we should be freed, but as the indispensable soil into which the living roots of our future will be sunk. We must recover the « faculty of feeling »(8) this ground, foundation of the earthly life. For as Masanobu Fukuoka said, « If one can experience participation in this cycle, feel it every day, nothing else is necessary. » Sap precedes blood. Blood comes from the ground. And it is perhaps in what we are now trying to destroy that we are looking for the most. What the song, or the poem, is most able to reveal: And he who knows how to see the earth lead to fruits, does not move the failure, although he has lost everything. (René Char)
Emmanuel Godinot, farm worker, musician.
- «Charte mondiale des sols», Food and Agriculture Organisation (FAO), 1982.
- Gis Sol. 2011. L’état des sols de France. Groupement d’intérêt scientifique sur les sols, p110.
- Claude Bourguignon, Le sol, la terre et les champs, Paris, Sang de la Terre, 2002, p.47.
- Cf. Jean-Pierre Berlan (sld.), La guerre au vivant, OGM et mystifications scientifiques, Marseille, Agone, 2001.
- François Terrasson, La peur de la nature, Paris, Sang de la Terre, 2007.
- Cf. Jean-Claude Besson-Girard, Decrescendo cantabile, Lyon Parangon, 2005.