Desertification

• 1. Introduction

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  Desertification is the slow transformation of fertile land into arid desert, driven by a combination of natural forces and human choices. Lake Chad, once one of Africa's great bodies of water, has shrunk by over 90% since 1987. Millions of people who once lived along its shores have been displaced, scattered by the retreat of water that sustained them for generations. That single lake tells a larger story: across the planet, a process is underway that threatens the livelihoods of more than two billion people who call drylands home.

  At least 90% of dryland inhabitants live in developing countries already struggling with poverty and limited infrastructure. When their land degrades, it does not simply become less productive. It becomes a place people must leave. Projections for sub-Saharan Africa suggest that the number of environmental refugees could grow from 14 million in 2010 to nearly 200 million by 2050.

  What causes fertile ground to become hardpan? How do natural cycles interact with farming, grazing, and climate change to strip the soil bare? And what are communities, governments, and international organizations doing to push back? The Gobi Desert is currently expanding at a rate of over 3,600 square kilometers of grassland turned to wasteland every year. The answers to those questions matter urgently.

• 2. The Ground Beneath Us

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  Vegetation is the keystone of soil stability. Studies have found that erosion and runoff decrease exponentially as plant cover increases. Remove the plants, and unprotected soil surfaces either blow away on the wind or get scoured off by flash floods. What remains is the infertile lower layer that bakes hard in the sun, forming an unproductive hardpan that resists both water absorption and root growth.

  The United Nations Convention to Combat Desertification defines the problem as land degradation in arid, semi-arid, and dry sub-humid regions resulting from climatic variations and human activities. As of 2005, more than 100 formal definitions of desertification existed among researchers and institutions. The Princeton University Dictionary's widely-accepted definition described it as fertile land transforming into desert, typically through deforestation, drought, or improper agriculture.

  Drylands cover approximately 40-41% of Earth's land area. Between 10% and 20% of those drylands are already degraded, with the total area affected by desertification estimated between 6 and 12 million square kilometers. Around 1-6% of dryland inhabitants live in already-desertified areas, but a billion people remain under threat from further degradation.

• 3. Human Hands, Natural Forces

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  Early research pointed to overgrazing as the primary culprit behind desertification. Cattle and livestock consuming vegetation faster than it could regenerate seemed like the obvious explanation for bare, eroded land. But the science has grown more complicated since then.

  Drought in the Sahel is now understood to be principally the result of seasonal rainfall variability driven by large-scale sea surface temperature changes, a pattern linked both to natural variability and to anthropogenic emissions of aerosols and greenhouse gases. Changes in ocean temperature, combined with reductions in sulfate emissions, have actually caused a partial re-greening of the Sahel in recent decades. Some researchers have concluded from this that agriculture-driven vegetation loss plays only a minor role in desertification.

  In China's Mu Us Desert, soil health accounts for 37% of desertification events, while meteorological and human factors work against desertification at 46% and 17% respectively. Inner Mongolia shows different proportions, with meteorological contributions at 24% and soil health benefits at 34.7%. Shaanxi provides a counterexample where meteorological factors actually work against desertification while soil conditions exacerbate it.

  The Sahara's own formation illustrates how deep natural cycles run. Scientists attribute the existence of the Sahara in its current location to variations in solar insolation caused by orbital precession of the Earth. These variations alter the strength of the West African Monsoon and trigger vegetation and dust feedback loops that amplify cycles of wet and dry climate. The transition from savanna to desert during the mid-Holocene may also have been partly accelerated by overgrazing from the cattle of local populations.

• 4. A Warming World, Expanding Drylands

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  Between 1982 and 2015, 6% of the world's drylands underwent desertification driven by unsustainable land use compounded by anthropogenic climate change. That figure comes from an observation-based attribution study carried out in 2020 that accounted for climate variability, CO2 fertilization, and both gradual and rapid ecosystem changes from land use.

  Anthropogenic climate change has degraded 12.6% of drylands, an area of 5.43 million square kilometers, affecting 213 million people. Of those affected, 93% live in developing economies. Climate projections suggest drylands will expand from covering 38% of continental land surface in the late twentieth century to 50% or 56% by the end of the current century, depending on whether emissions follow the moderate or high-warming pathways known as RCP 4.5 and RCP 8.5. The regions expected to see the most expansion include southwest North America, the northern fringe of Africa, southern Africa, and Australia.

  Dust storms have risen markedly as dryland soils have become more exposed. Global annual dust emissions increased by 25% between the late nineteenth century and today. In the Middle East, dust storms are described as becoming more frequent and intense in recent years, as long-term reductions in rainfall lower soil moisture and strip vegetative cover. Those storms scatter incoming solar radiation, raise atmospheric temperatures, and can shorten the lifetime of clouds, further reducing rainfall in an accelerating cycle.

• 5. Food, Migration, Conflict

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  Europe imports over 50% of its food on average, a figure that underscores how dependent the world has become on agricultural land that increasingly sits in dryland regions. Around 44% of agricultural land is located in drylands, and it supplies 60% of the world's food production. As desertification removes land from productive use, the gap between supply and growing demand narrows.

  In Nigeria, Sudan, Mali, and other countries of the Sahel, conflicts between herders and farmers have intensified because of land degradation, climate change, and population pressure. Rural land can no longer support the same populations that previously farmed it, driving mass migration toward cities and creating unemployment and slums.

  Mongolia presents a specific case study. Around 90% of its land is fragile dryland, and the UN estimates 90% of Mongolia's grassland is vulnerable to desertification. The country's mean air temperature increased by 2.24 degrees Celsius between 1940 and 2015, and precipitation dropped by 7% over the same period. A shift from sheep to goat farming to meet export demand for cashmere wool has further damaged grazing lands; goats eat roots and flowers, causing more harm than sheep. In Mexico, roughly 1,000 square kilometers of land have been lost to desertification each year, with similar displacement pressures playing out in Central America, Bolivia, Chile, Ecuador, Peru, Argentina, and Paraguay.

• 6. Planting Back the Desert

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  China's Great Green Wall was proposed in the late 1970s and is not expected to be completed until 2055. According to Chinese reports, nearly 66 billion trees have been planted as part of the project. The wall has reduced desert land in China by an annual average of 1,980 square kilometers and cut the nationwide frequency of sandstorms by 20%.

  In Niger, a technique called Farmer-Managed Natural Regeneration, or FMNR, has been applied since 1980. This low-cost approach involves selectively pruning shrub shoots to allow native trees to sprout from existing root systems. Farmers have used it to regenerate approximately 30,000 square kilometers of degraded landscape. The Humbo Assisted Regeneration Project in Ethiopia uses the same techniques and has received funding from the World Bank's BioCarbon Fund.

  Africa's Great Green Wall initiative, launched by the African Union in 2007, aims to run a belt of vegetation 8,000 kilometers wide across the entire width of the continent. The project has attracted 8 billion dollars in support and has already restored 36 million hectares of land. By 2030 it aims to reach 100 million hectares. In Nigeria alone, the project has created over 20,000 jobs. Senegal has contributed by planting 50,000 acres of trees, with reported improvements in land quality and local economic opportunity.

  Contour trenching offers another tool: digging trenches 150 meters long and 1 meter deep, parallel to landscape height lines, stopping water from flowing away and causing erosion. Stone walls placed around the trenches prevent them from collapsing. The technique was invented by Peter Westerveld. A 2025 peer-reviewed study published in Scientific Reports found that in the Kubuqi desert of northern China, which receives roughly 300 millimeters of annual rainfall, agrivoltaic systems improved microbial count, soil quality, and nutrient content more than either non-solar plantings or solar-only installations, with panel shading reducing soil temperature and limiting evaporation.