When we talk about biodiversity and ecology, soil is often forgotten. However, it is obviously essential for agricultural production, but also for the many services it provides us. Knowing it better, with the help of new technologies, also means better protecting it.
Every year, France loses between 20 and 30,000 hectares of natural, agricultural or forest areas under the pressure of human activities. This destruction of the soil endangers living things in general and the human species in particular. Soils play a fundamental role: production of plants, renewal of the nutrients necessary for their growth, carbon sequestration, water regulation, maintenance of biodiversity, etc. The use of satellites can help to better preserve them.
Air and water have benefited for many years from regulations and monitoring systems for their quality at national and European levels. The ground is far from having such an arsenal to protect it. Since July 2023, a European directive relating to soil monitoring and resilience has been under discussion. But the only laws passed in France in recent decades only took into account the risks concerning contaminated sites.
However, the pressures exerted on the soil have diverse origins and are mostly linked to human activities: industrial development, urbanization and agricultural production do not only result in its contamination. They also lead to problems of waterproofing and soil compaction which prevent the absorption of rainwater. All of these elements generate a loss of soil biodiversity which nevertheless represents a quarter of terrestrial biodiversity.
Little by little, the role of soils is recognized
Awareness of these threats is growing. At the national level, first of all, the Climate and Resilience law of August 22, 2021 has set the objective of achieving zero net artificialization by 2050. It aims to better take into account the environmental consequences of new constructions and land developments. Furthermore, since 2000, the soil quality measurement network has evaluated and monitored the quality of French soils in the long term, using samples.
At the continental level, the European Union built, in 2009, the LUCAS surveillance network (Land Use and Coverage Area Frame Survey) intended to control land use and cover. But LUCAS was mainly interested in the physical and chemical composition of soils; the description of biodiversity was not taken into account. This oversight was corrected in 2018: that year, in its quest for information, LUCAS integrated data on soil biodiversity including, among other things, bacteria, fungi, arthropods, earthworms, etc. At a global level , finally, a UN resolution included, on September 25, 2015, soil protection as one of the elements of the sustainable development program for 2030.
This new consideration for soils can be compared with a renewal of agricultural practices. Conventional cultivation systems using a significant quantity of chemical inputs (fertilizers, herbicides, pesticides) indeed need physical and chemical data on the soil. The quantification of organic carbon, the pH which determines the acidity of a soil and the availability of nutrient elements such as phosphorus are useful information with the objective of agronomic performance and yield.
But these indicators are no longer suitable when it comes to farms in transition towards agroecology. Indeed, the priority of such operations is to promote a biological balance in the soil. This is consistent with the awareness of the different functions fulfilled by biodiversity: renewal of nutrients for plants, regulation of pathogens, transformation of carbon in the soil, stability of its structure, etc. However, this awareness is struggling to gain traction. path in the minds of citizens. It is first of all the monetary value of the land that appears to them.
New technologies to support the transition to agroecology
In order to highlight all the other types of value that soil holds for life in general and human life in particular, the European Union has undertaken to launch numerous projects. One of them consisted of creating a decision support tool called Soil Navigator : its role is to quantify soil functions (production of agricultural and forestry biomass, water purification and regulation, carbon sequestration, habitat for diversity, nutrient cycle) on a European scale. This tool nevertheless relies on the knowledge of a certain number of soil descriptive variables whose acquisition can be expensive or difficult to access for farmers.
Tools like sensors or satellites can help farmers make the best choices in terms of fertilizer, pesticide or herbicide use. Large space groups, companies involved in the Internet of Things or manufacturers of agricultural equipment are contributing to the development of tools to support the ecological transition.
Since 1985, the European earth observation program Copernicus participated in the creation of the database CORINE Land Cover (CLC). It draws up an inventory of land use: cities, forests, crops, etc. thanks to the visual interpretation of satellite images. Today, the Copernicus program is based on the deployment of Sentinel satellites. The information they provide about land cover and its changes, land use and vegetation condition are also valuable tools for land management. common agricultural policy.
Numerous and less expensive data to help farmers take care of the soil
Today, data is provided by more and more media (satellites, planes, drones, tractors, etc.) and is therefore ever more numerous. And it is not always necessary to rely on space or the sky to obtain them: sensors placed directly in fields, on tractors or on agricultural machines provide farmers with detailed information on acidity, the temperature and humidity of their soil. They allow them, for example, to predict the weather conditions for the days and weeks to come and, thus, to take the necessary measures for the protection and yield of their crop.
Remote sensing is widely used in agriculture, particularly for vegetation monitoring. Drones and satellites provide recommendation maps that can be connected to agricultural equipment, allowing adjustment of inputs, early detection of diseases and creation of yield maps. These aspects, particularly the physico-chemistry of soils, have been widely studied in the literature.
On the other hand, the study of the biological functioning of soils as well as the relationships between management practices and their consequences on ecosystem services have not or rarely been examined using remote sensing. These issues linked to soil and remote sensing are currently the subject of projects on a national scale such as the SolNum project carried out by UniLaSalle within theH@rvest Alliance.
In 2019, the European Commission presented a plan: the European Green Deal (European Green Deal) which has the objective of reducing greenhouse gas emissions by at least 50% in 2030. The new tools offered to European institutions and, among other actors, to farmers to achieve this goal are increasingly numerous. Digital solutions and mathematical methods of image processing obtained through Earth observation from satellites, drones or simply tractors can help to get closer to this objective. If there is still a lack of perspective on the use of these new tools, we can hope that they contribute to better understanding the soil and, thus, to better protecting it.
In the field of knowledge of their soil, the use of space and digital technology also provides farmers with tools that ultimately cost them less. The annual subscription to a database represents a much smaller investment than regular drilling or sampling and their analyses. In addition, the prodigious amount of information that it puts at their fingertips allows them to make relevant agronomic decisions. Spatial and digital technology truly represent new tools to be used to protect soil biodiversity.
This article benefited from the support of Jean-Marc Pitte, journalist and scientific mediator. We thank him for his help in popularizing this reflection.
