Desertification is not the spread of deserts. It is the slow degradation of fertile land – a process that now affects 40 percent of the Earth's land surface and leaves around 100 million hectares of healthy land unproductive every year. As governments gather in Mongolia this week for the UN's Cop17 desertification summit, scientists say restoring soil health is becoming critical for food security, livelihoods and climate resilience.
The summit's theme is "Restoring Land, Restoring Hope" and delegates are expected to discuss ways to tackle drought and land degradation, including the Riyadh Global Drought Resilience Partnership launched at Cop16 in Saudi Arabia in 2024.
Under the initiative, €10.3 billion was pledged over seven years to help 74 vulnerable countries cope with drought and restore degraded land.
Jean-Luc Chotte, a soil expert at France's National Research and Development Institute (IRD) and chair of the French Scientific Committee on Desertification, spoke to RFI about the causes of land degradation and why agroecology is increasingly being seen as part of the solution.
RFI: What does the term "desertification" actually mean?
Jean-Luc Chotte: Desertification is not the advance of the desert. It refers to soil degradation – the deterioration of the soil’s physical, chemical and biological properties – observed in areas with arid, semi-arid and dry sub-humid climates.
But these places are not deserts: farmers, herders and many other people live there. The term "desertification" is therefore misleading.
RFI: What is the difference between aridity and drought?
JLC: Aridity describes a type of climate – and is therefore a long-term phenomenon – in terms of water availability. It refers to areas where potential evapotranspiration is between 1.5 and 20 times greater than the average amount of rainfall.
A drought is an exceptional period of water scarcity affecting ecosystems and human populations. It is attributed to below-average rainfall compared with seasonal norms, high temperatures, wind, a lack of water in the soil which limits the growth of crops and pasture, lower water levels and reduced flow rates in watercourses, and a drop in the levels of reservoirs and groundwater tables.
RFI: Since Cop16 in 2024, France has officially been included on the list of countries affected by desertification. Why is this?
JLC: France attaches great importance to this issue. In 1997, three years after the UN Convention to Combat Desertification (UNCCD) came into force, it set up a scientific committee on desertification (CSFD) to understand what is happening and to take action based on the most up to date scientific evidence.
In preparation for this decision, the CSFD worked with Data Terra and the NGO Nitidae to identify the parts of mainland France subject to arid, semi-arid and dry sub-humid climates.
This corresponds to the Mediterranean coastline, representing just under 2 percent of French territory. Of this area, approximately 0.14 percent is degraded, according to the three indicators recognised by the parties to the UNCCD, which define land degradation: trends in land use (agricultural, urban, etc), trends in productivity and soil carbon stocks.
These three indicators were then applied across the whole of France. In mainland France, 3 percent of the land area is degraded.
However, these three indicators reflect only part of the degradation processes. We therefore expanded the study by adding other relevant indicators, based on French research expertise, such as erosion (by wind or water), metal pollution, loss of biodiversity, decline in vegetation, salinisation and landslides. As a result, 77 percent of soils across France are degraded.
RFI: What are the physical symptoms of desertification in an arid climate?
JLC: These include soils that are dry on the surface and do not allow water to seep in; soils subject to wind erosion, with particles of dust or sand carried over distances from one plot to another or from one continent to another; yellowing plants lacking water and nitrogen, and a landscape stripped of trees. If you dig a hole, there is no life – the roots of the remaining vegetation are shallow. Ultimately, this is also evident in a decline in agricultural yields.
RFI: What are the causes?
JLC: This land degradation is mainly due to the misuse of land through human activities.
RFI: What constitutes poor land use?
JLC: It is pushing the land’s productive capacity beyond its natural resources. This is done through ploughing, monoculture, applying too much fertiliser, or reducing the stock of organic matter in the soil. The model of intensive agriculture. In livestock farming, if animals are no longer free-ranging on pastoral lands, or if the stocking density exceeds the land’s capacity to provide forage, we are on a path towards degradation. The situation will worsen if these practices are not changed. That is why issues such as herders’ mobility, crop rotation, the role of trees in the landscape and agroforestry are fundamental.
These harmful practices are exacerbated by climate change. As temperatures rise, there is greater evapotranspiration. Similarly, if rainfall is distributed very differently over the course of the season this exacerbates the effects of land degradation, because farmers will adopt more intensive farming practices in order to feed themselves and generate an income.
Furthermore, soils are the largest terrestrial carbon sink on a global scale. By degrading them, we find ourselves in a vicious circle where the harmful effects of land misuse accelerate climate change.
RFI: What are the economic consequences for local populations?
JLC: When we consider the decline in crop yields and the nutritional needs of populations, which are set to rise, we are heading towards a rather significant gap. It will be vital to meet these needs in order to prevent migration. Not just between Africa and Europe. The largest migration flows occur between rural and urban areas, within a country or between neighbouring countries.
That is why, at the 1992 Earth Summit in Rio, Africans called for a convention on desertification that would highlight the challenges they face.
RFI: How can this be remedied?
JLC: The key factor in combating soil degradation is the organic matter in the soil, which creates the conditions for its fertility, productivity and ability to retain groundwater. The more organic matter there is, the more space the minerals leave, which can be filled with water and living organisms such as bacteria, fungi and nematodes. Many agricultural practices therefore involve adding organic matter to the soil.
It is perfectly possible to be in an arid region and adopt practices that prevent soil degradation, or even restore the soil. In mid-April, I was in the Ferlo, in northern Senegal, where the Fulani, a nomadic pastoralist people, live. There are areas that are not degraded. The soils are low in organic matter, but there is still vegetation, and trees are intermingled with crops or livestock.
The flagship Great Green Wall project was set up to restore all these lands south of the Sahara. It was not intended to act as a bulwark against the advance of the desert with a uniform 7,000-kilometre hedge of a single tree species stretching from Dakar to Djibouti, as some might have imagined. The Sahara is hardly advancing at all.
One might criticise this project, which has not lived up to its ambitions. But it is a tremendous African initiative that also combats climate change, even though African countries have emitted fewer greenhouse gases than others.
RFI: Agroecology, a sustainable approach to farming that works with nature, has been presented as the solution to desertification, with a view to achieving a sustainable food system. Yet it is struggling to establish itself as a model. Why is this?
JLC: The term "agroecology" first appeared a few years ago. It is becoming increasingly widespread, and I do not see any rejection of agroecology. We are on the right track.
The term has emerged because, on the one hand, civil society organisations have done a tremendous job of raising awareness and lobbying, and on the other hand, because scientific research has produced data showing that agroecological practices improve a number of indicators.
RFI: So what are the obstacles to widespread adoption of this? Is it the fact that it has never been tested on a large scale in terms of productivity and profitability?
JLC: I believe that the obstacle to practising agroecology on a large scale is entirely linked to the fact that we only take into account one of the soil’s functions – namely production and generating income. We must also consider other aspects, such as carbon sequestration in soils, the maintenance of biodiversity, combatting land degradation, farmers’ incomes, efficiency and organic matter stocks. The UN's Food and Agriculture Organization (FAO) lists the 10 elements of agroecology.
However, it is not a model that can simply be copied and pasted without considering whether it is suited to the socio-economic constraints of the regions: land ownership issues, limited access to finance, markets or technical support, inconsistent public policies and so on. It is all of these factors that delay scaling up.
Policy-makers then wonder how they can verify the positive impact of its implementation. And this is where we need to be able to encourage policymakers to consider other aspects.
There are an increasing number of tools available for documenting agroecological practices. The FAO’s digital tool, Tape, has been adopted by public authorities and farmers. At IRD, we are developing our own tool, Bio Functool, but this is easier when you are a research laboratory than when you have the resources of an NGO.
RFI: Is there a country where agroecology is already well established?
JLC: In 2019, Senegal launched Dytaes – an initiative by civil society and scientific organisations that have documented agroecological practices across the country in order to use them as a political lever.
We have been working in [the Senegalese village of] Diohine for 10 years, alongside the villagers. We have reintroduced certain practices, such as planting Faidherbia albida groves. This tree, which is well-suited to the region, sheds its leaves during the rainy season.
This means that the crops grown beneath these trees do not compete for light, as the tree no longer has any leaves. It also has deep roots capable of drawing water from the water table and bringing it up at night to release it back to the surface. Farmers can therefore diversify their crops: watermelon, sorghum and millet. They are also increasingly careful to allow young Faidherbia shoots to grow rather than uprooting them, as was the case in the past.
There are a great many agroecological projects in West Africa – such as Sustain Sahel – which aim not only to slow down soil degradation or restore degraded soils, but also to provide an income for local farmers and establish value chains for the marketing of their produce. There are also such projects in Ethiopia.
RFI: The Cop16 on desertification, held in Saudi Arabia, ended in failure. What makes you think this one will yield better results?
JLC: Without downplaying the fact that we are often very disappointed by the progress made, these international meetings are essential. They are where major environmental challenges are discussed, bringing together researchers, civil society organisations and public and private decision-makers. They also enable me, as a scientist, to better understand how the knowledge and data I produce can inform and guide policy-making.
The failure of the Cop in Riyadh is mainly due to the fact that states were unable to agree on the role of drought within this convention. Science had already done its part beforehand within the Intergovernmental Panel on Drought. Now, it is clearly a political issue, and we are all aware of the current state of global geopolitics.
This article has been adapted from the original interview in French by Géraud Bosman-Delzons.
