When the Earth turns to dust: can we save the last of our soil?

Africa, Tera, Niger - Dry sahelian semi-desert region around Tera (Credit: FAO/Giulio Napolitano)

The Cop15 summit against desertification held from 9 to 20 May has gathered the leaders of 197 countries in Abidjan, Ivory Coast.

Dubbed as one of “the greatest environmental challenges of our times”, desertification already affects 500 million people in 168 countries, and a third of the planet’s surface. This phenomenon is only accelerating with global warming, with the ground slipping away from under humanity’s feet.

Why is soil important? Known as the Earth’s living skin, it provides 99 per cent of the food on which humans depend on. Overexploited by human activities, it is eroding, drying up, and being depleted of its nutrients. According to the United Nations, 40 per cent of the world’s lands are already degraded, affecting half of its population. The main cause intensive agriculture, which is responsible for 90 per cent of global deforestation, is the main cause.

Coupled with global warming, arable land degradation is intensifying and accelerating,occurring at 30 to 35 times the historical rate. If these trends continue, an additional area the size of South America, could be lost by 2050. 

What is desertification? “Contrary to what one may think, desertification is not the natural expansion of deserts, but the retreat of land,” explained Gudrun Schwilch, head of the soil section at the Swiss Federal Office for the Environment (FOEN), and former researcher at the Centre for Development and Environment (CDE) at the University of Bern. 

This nuance indicates the implication of human activity. “Human activities, such as deforestation, urbanisation, intensive agriculture, overgrazing, and inadequate irrigation practices, are the main causes of desertification,” Schwilch continued. 

The United Nations Convention to Combat Desertification (UNCCD) defines the phenomenon as land degradation in arid (semi-desert), semi-arid (savannah) and dry sub-humid (pasture) areas due to human activities and climate change. 

Arid lands, which are considered to be inhospitable, cover 45 per cent of the world’s land surface and host a third of the world population as well as unique endemic flora and fauna. Desertification is threatening this fragile equilibrium as it looms large over one third of the planet’s land surface that could become uninhabitable.

Climate change not the only cause. Schwilch points out that global warming is only one of the several aggravating factors: “Extreme weather events such as droughts, storms and heavy rains only worsen soil erosion.”

And the warmer the atmosphere, the more soil erosion accelerates. Edouard Davin, professor of climate scenarios and sustainable development at the University of Bern, and co-author of a 2019 IPCC special report on land use, explained: “In arid regions, global warming decreases the availability of water resources in soil by accelerating surface water evaporation. As more of the forests dry out and become more fragile, the more land is exposed to erosion.” 

By the end of April, humanity crossed the sixth planetary limit of “green water” – water available to plants, particularly through soil moisture and evaporation. 

A vicious circle. Desertification creates an unbalance in ecosystems, leading to a loss of biodiversity, which in turn accelerates global warming by releasing greenhouse gas emissions. 

“One third of the earth’s carbon is stored in arid and semi-arid regions, in the forests, but especially in soils. When soil deteriorates, it releases this CO2 into the atmosphere, which increases global warming. It is a vicious cycle!” Davin stated. 

Beyond the damage to ecosystems, desertification has a human and socio-economic cost. Schwilch pointed out: “the depletion of soil organic matter compromises agricultural harvests and can push farmers into poverty, causing them to abandon their land. This is already the case in Spain and Morocco for example.”

Every year, 120,000 square kilometres of arable land are lost to desertification — three times the size of Switzerland, and enough to produce 20m tonnes of cereals, according to the UN. With 9.9 billion people to feed by 2050, compared to 7.8 billion today, this is also an emerging challenge for global food security.

Geographic distribution of arid, semi-arid, dry sub-humid, and humid lands, according to the Aridity Index (AI) (Credit: IPCC Special Report 2019 (Fig 3.13) / Abatzoglou et al. 2018)

While two-thirds of the African continent is already plagued by desertification, the phenomenon extends far beyond its borders. “Africa, China, India, and South America are already severely affected by desertification. But this is actually a global problem that does not only affect developing countries,” noted Schwilch. 

From vicious circle to virtuous circle. However, this trend is not (yet) irreversible. “The most important thing is to protect the soil before we reach a tipping point,” said Schwilch. The leaders of the C15, meeting in Abidjan until 20 May, will discuss major initiatives, such as the Great Green Wall. Since 2007, the project aims to restore 100 million hectares of arid land on a strip of 8,000 kilometres from Senegal to Djibouti. 

Schwilch welcomes initiatives such as this one, while cautioning such gigantic reforestation projects. “Re-greening a desert would not make sense. It is essential that projects prioritise regions that are still partly fertile, so that they benefit the local populations who must be involved in the process. Sharing knowledge, especially regarding native tree species, is essential for sustainable land and water management,” she said.

The Great Green Wall of the Sahara and Sahel, initiated by the African Union to combat the effects of climate change and desertification, will cross the entire African continent over 7,800 kilometres. (Credit: IPCC Special Report 2019 (Fig 3.13) / GlobCove)

Davin, who just returned from Kenya where he witnessed a reforestation project involving the parachuting of seeds with drones into desertified areas said: “Some initiatives are promising, but reversing the vicious cycle is often complicated. Planting trees will not be enough. It is imperative to slow down global warming and to curb over-exploitation of the soil. We must not only treat the symptoms of desertification, but also the causes.” 

Agroecology, a way forward?  To safeguard the precious resource under our feet, experts are calling for a change in the way land is used, particularly advocating for more sustainable farming practices. According to the UN, agroecology can double agricultural productivity in a decade. 

“There are already proven techniques to reduce soil erosion, such as ploughing less and better crop rotation,” said Davin. 

While welcoming these sort of initiatives, Schwilch points out  the economic challenges they pose. . “Today, food from unsustainable intensive agriculture costs less than organically produced food for consumers. Prices do not reflect the real costs to the environment, and the food insecurity they will plunge our societies into in the long run,” she said.


This article was first published in Heidi.news in French. It has been adapted and translated to English by Geneva Solutions.