PARIS — The European Conservatory of Soil Samples (CEES) is an elegant, single-story building that was partially constructed using soil from its foundations, through the ancestral technique of rammed earth. Located near Tours, southwest of Paris, it is part of the INRAE Val de Loire center, a research institute working for greater sustainability of natural resources, agricultural and forestry systems and the biodiversity associated with them.
For the latest news & views from every corner of the world, Worldcrunch Today is the only truly international newsletter. Sign up here.
On its on 8 kilometers of shelves, the conservatory houses tens of thousands of soil samples. But what is the purpose of archiving these samples?
The answer is that the precious services that soil provides, including carbon storage and rainwater retention, are under threat. And they are being undermined by human activities that are dislocating their astonishing and oftentimes hidden richness. It is hard to imagine, but 25% of the world’s biodiversity hides underground. A living capital that we must learn to protect, an effort that requires knowing and studying it.
A complex ecosystem
“Everyday, the conservatory receives about 50 kilograms [110 lbs.] of soil, ” explains Antonio Bispo, director of the research unit Info&Sol at INRAE. The majority of the samples come from two major campaigns that involved 2,200 plots of land, the second of which is ongoing and will continue until 2027. “The samples are processed and sieved by the CEES,” says Bispo. “Then, some are sent to other INRAE laboratories for analysis.”
Still a rarity in Europe, the conservatory has allowed France to assess the conditions of its soil in 2011, revealing a highly complex ecosystem. Dirt is composed of a mix of mineral and organic elements, of which a large share comes from the decomposition of plants and animals. This forms what is known as humus, the dark organic matter in soil, which contains chemical particles such as carbon, nitrogen, phosphorus, sulfur and trace elements like calcium and selenium.
61% of European soil degraded
But soil is also home to countless living organisms. Depending on the substrate, every gram of dirt hosts up to 1 billion bacterias and 1 million fungi, but also viruses, protists, nematodes and more. They cohabit with a whole mesofauna, still very poorly cataloged, measuring in the millimeters, such as springtails, tardigrades or mites. There is also macrofauna, made up of millipedes, termites, ants and above all earthworms, considered to be the soil’s engineers. Soil is therefore the end result of highly interlinked physico-chemical and biological processes, and we are still far from pinpointing all the reasons for this.
We know with certainty that intensive agriculture has greatly altered soil quality.
Yet, what we know with certainty is that intensive agriculture has greatly altered soil quality. Last year, a study carried out by the EU Soil Observatory on 15 indicators, including pollution, erosion, carbon and biodiversity loss, showed that 61% of the analyzed samples were degraded.
A subsequent study on French soils, found that 98% of the 30 analyzed sites contained at least one pesticide. A total of 67 molecules were found, mainly fungicides and herbicides. “Some of them have been banned for years,” says microbiologist Marc-André Selosse.
More and more fertilizers
The author of a book on the natural history of soil, L’Origine du monde (The Origin of the World), Selosse points to the deleterious effect of synthetic nitrogen fertilizers, which have been feeding conventional agriculture for decades. Nitrogen fertilizers are also dangerous pollutants for water bodies, plants, animals and humans, and they contribute to climate change through emissions of nitrous oxide.
“Thanks to these mineral inputs, the plant no longer needs to interact with mycorrhizal fungi in the soil, which normally run errands for it via their mycelium network, exchanging nutrients for sugars,” Selosse says. That, he explains, is a major problem: “By entering into symbiosis with plant roots via their filaments, these fungi also protect them from aggressors.”
Their absence must therefore be compensated for by an increasing number of synthetic phytosanitary products. Jean-Pierre Sarthou, professor and researcher at the Toulouse School of Agricultural and Life Sciences, says that “to obtain the same quantity of cereals, we need to use four times as much nitrogen fertilizer as we did a century ago.”
Soil impoverishment is also responsible for soil condensing (compaction). “If organic matter is lacking, the porosity of the surface is altered, soils become smooth, water no longer infiltrates and when it rains it runs off, favoring erosion,” Sarthou explains. “After a storm, several dozen tonnes [of soil] per hectare can be washed away”.
An exhausted model
Established in the aftermath of World War II, at a time when it was necessary to increase yields to feed the planet, our agricultural model is today, many say, exhausted. “Productivity is leveling off, and operation costs are rising. This increase in costs is partly due to soil impoverishment, which, depending on the weather, are either soaked or compacted. Today, to use the same plough, you need tractors that are 25% more powerful,” Sarthou says.
For Claire Chenu, research director at INRAE and professor at AgroParisTech , the solution to this problem is “putting agronomy into farming.” In other words, this implies encouraging people to take care of soil by putting it back at the heart of farming.
A real paradigm shift, as until now soils have been seen as mere supports to be amended. “Although there are still a lot of researchers who haven’t given up on the intensive model, the scientific community has taken up the subject and is trying to move it forward,” Selosse says. But there is also still a great deal of resistance on the part of farmers.
Organic farming, far from ideal
“We have to show [farmers] that it is more profitable for them to change their model and start farming sustainably,” says Jean-Christophe Girondin-Pompière, founder of the AgroLeague platform, which is committed to helping farmers make this transition.
But toward which model? 100% organic farming? Desirable but not realistic. In France, many farmers who switched to organic are now turning back; the recent purchasing power crisis has shown the limits of the model. Not to mention that, on a purely agronomic level, there are a few counter-intuitive truths to be remembered.
While organic farming is undoubtedly the best for preserving human health, it is not necessarily what’s best for soil life. Because organic farmers are not allowed to use herbicides, they have to plough their fields, at least superficially, before sowing to prevent weeds from taking up all the space.
But plowing is a major contributor to the destruction of soil life. Selosse explains that “not only it breaks up the mycelium networks of fungi, but by aerating the soil it brings oxygen to the bacteria, which will then consume more organic matter, essential to its porosity and fertility”.
An ambitious, but not rigid model
Denis Laizé, a farmer in the Maine-et-Loire department who recently switched to organic farming, has seen this loss of biodiversity first hand, thanks to a rudimentary test for counting earthworms that involved pouring a mixture of water and mustard over 1 square meter of soil. An irritating potion that brings the earthworms to the surface. “Today, I have four times fewer than before,” he says.
Before adopting organic agriculture, Laizé was not practicing conventional agriculture, but conservation agriculture. A model that is starting to catch on, as it is the best possible compromise between yield requirements and soil regeneration.
François Mandin, a farmer in the Vendée department and the president of the French association for sustainable agriculture (Apad), which promotes conservation agriculture, explains that this method is based on three principles. “Practice permanent cover, in other words, never leave the soil bare during intercropping periods. Vary the species planted, if possible mixing cereals with legumes, which have the capacity to capture and transmit nitrogen from the air. And finally, work the soil as little as possible, using what we call direct seeding”.
Even though it is not ideal, healthy soils can absorb a small quantity of herbicides with minimal impact.
This means using a little herbicide before sowing; “As little as possible, but as much as necessary,” says Laizé. In short, this hybrid model is ambitious but not rigid. Mandin says he has increased the organic matter in his soil by 2 points since using this method. “Even though it is not ideal, healthy soils can absorb a small quantity of herbicides with minimal impact,” says Sarthou. A lesser evil, then, pending a hypothetical natural alternative.
Although many farmers are intermittently adopting conservation agriculture methods, it is estimated that only 4% of land in France is farmed according to these principles. Through his association and its 12 regional delegations, Mandin aims to increase this number to 30% by 2050. An ambitious goal.
“Many farmers see giving up plowing as a real cultural change that requires learning, and therefore involves a degree of risk,” Laizé says. Hence the importance of supporting them. In theory, this is the job of the chambers of agriculture, but “while they are not hostile, they are not very proactive,” Selosse says. All the more so, as this model does not favor the agrochemical business and farm equipment dealers.
However, attitudes are changing. Last December, the Maine-et-Loire Chamber of Agriculture organized a major technical day on conservation agriculture. “Today, we’re helping 300 farmers in 27 groups to convert to this model,” says Laizé, who also heads the organization’s agronomy department.
The risk of greenwashing
Farmers can also rely on new private platforms such as AgroLeague, which claims to be “the first personalized agronomic service dedicated to farmers.” AgroLeague employs around 30 agronomists and works with 6,000 farms across France.
But conservation agriculture will also need the support of the agri-food industry to develop. That is one of the aims of the Earthworm Foundation’s Sols vivants (Living Soils) initiative. Mandated by groups such as Nestlé, Lidl and McCain, it supports suppliers in their conversion toward regenerative agriculture.
Here again, the process is gradual. Brands prefer to talk about regenerative agriculture, perceived as a more powerful term than conservation agriculture. But in the absence of strict specifications, this model leaves the door open to greenwashing. “We see ourselves first and foremost as advocates for the soil,” says Bastien Sachet, managing director of the Earthworm Foundation.
Legislative setbacks
Things are now moving, at least on the ground. From a legislative and political point of view, however, soil is clearly not yet a priority. In February, the French Senate rejected a bill put forward by the Socialist, Ecologist and Republican groups aimed at recognizing soil as a heritage asset and granting it the same level of general legal protection attributed to air and water in the country.
A European directive is also in preparation, but it is already failing to live up to expectations. “The text has already been amended,” says INRAE’s Chenu, who is also in charge of the European Joint Programme on agricultural soil management. “Originally, the emphasis was on soil health. Now we’re only talking about monitoring and resilience,” she says.
Better than nothing
In practice, soil remains a highly sensitive topic. Matthieu Dubernet is the president of TerraMea, a start-up that offers a new approach based on cytometric analysis, used for human health purposes, combined with infrared rays in microbiological analysis of dirt. For him, and many other proponents of soil regeneration, the problem lies in the method.
“We’ve got to stop fighting over who’s right and who’s wrong. We’re in the process of moving from an injunction to use agrochemical means to another, to use agroecological means,” he says. “The most important thing is for farmers to put the soil back at the heart of their model. Then they need to be given regeneration objectives, and let them choose the best strategy for achieving them.”
In a context marked by numerous setbacks on the ecological front, this might not be enough to trigger a revolution in the field and restore soil capital from top to bottom. But in the absence of a better solution, this is probably the best card to play at present.
