Desertification is the slow process of turning fertile land into dry, desert-like areas. This happens because of both natural events and human actions.
The main reason desertification occurs is the loss of most plants. This can be caused by many things, such as drought, changes in weather, farming practices, too much grazing by animals, and cutting down trees for fuel or building materials. Plants help protect the soil, and research shows that more plant cover greatly reduces soil erosion and water runoff. Without plants, dry soil is easily blown away by wind or washed away by sudden floods. This leaves less fertile soil layers that become hard and unable to grow plants.
More than 90% of people living in dry areas are in developing countries, where they often face poor economic and social conditions. These problems are made worse by land degradation because it lowers the land's ability to produce food, makes living conditions harder, and limits access to resources and opportunities.
Areas most affected by desertification include parts of Africa (like the Sahel), Asia (such as the Gobi Desert and Mongolia), and some parts of South America. Drylands cover about 40–41% of Earth’s land and are home to over 2 billion people. Effects of desertification include dust storms, lack of enough food, and increased poverty.
Ways to reduce or stop desertification include improving soil health, planting more vegetation, managing how animals graze, and planting trees (reforestation and afforestation).
Throughout Earth’s history, deserts have formed naturally over very long periods. The modern study of desertification began with research on the drought in the Sahel during the 1980s.
Definitions
Desertification is the slow process of soil becoming drier over time. According to the United Nations Convention to Combat Desertification (UNCCD), desertification is described as "land degradation in dry areas, such as arid, semi-arid, and dry sub-humid regions, caused by factors like changes in climate and human activities."
A desert is a region where the total rainfall and snowfall each year is much less than in other areas. Specifically, a desert is defined as an area where the average yearly rainfall is less than 25 centimeters. The United Nations Organization (UNO) defined desertification in 1995 as "land degradation in dry, humid, and sub-humid areas caused by climate changes and human activities."
By 2005, there was much debate about the correct definition of desertification, with over 100 different definitions existing. The most widely accepted definition came from the Princeton University Dictionary, which described desertification as "the process of fertile land turning into desert, often due to deforestation, drought, or farming practices that harm the land." This definition showed how desertification is linked to human actions, especially how land is used and managed. It also explained the effects of desertification on the economy, society, and environment. However, the earlier idea that desertification meant deserts growing physically larger has been replaced as the concept has developed further.
There is also debate about how to classify different types of desertification, such as the usefulness of terms like "man-made desert" and "non-pattern desert."
Causes
Desertification happens when most of the plants in an area disappear. This can be caused by several things alone or together, such as drought, changes in weather, farming practices, too many animals eating plants, and cutting down trees for fuel or building materials. Although plants are important for keeping soil healthy, research shows that more plant cover greatly reduces soil erosion and water runoff. When soil is not protected, it can be blown away by wind or washed away by sudden floods, leaving behind dry, hard soil that cannot support life.
Earlier studies suggested that overgrazing, where too many animals eat plants, was a major cause of desertification. However, recent research shows that overgrazing may not be the main reason in some areas. In the Sahel region, drought is now believed to be mostly caused by changes in rainfall patterns linked to ocean temperatures and human activities, such as emissions from pollution and greenhouse gases. These changes have led to more plant growth in the region, making some scientists think that farming-related plant loss has a smaller role in desertification than previously thought.
The number of people in an area affects how much land is overused for farming, grazing, and cutting down trees. Methods that were once acceptable are now causing harm because they are not sustainable.
Farmers often choose intensive farming over extensive farming to get more crops. This requires more fertilizer, pesticides, and workers to manage machines. However, using the land heavily and repeatedly drains the soil of nutrients, leading to desertification.
Scientists believe that the Sahara Desert formed naturally due to changes in how much sunlight reached Earth, caused by Earth's orbit around the Sun. These changes affected weather patterns, such as the West African Monsoon, which in turn influenced plant growth and dust levels. Some evidence suggests that overgrazing by people may have also contributed to the Sahara changing from grasslands to a desert during the middle of the Holocene period.
Studies in different areas show that human actions, soil health, and weather are all important in causing desertification. In the Mu Us Desert, soil health is responsible for 37% of desertification events, while weather and human activities reduce this by 46% and 17%, respectively. In Inner Mongolia, weather causes 24% of desertification, while soil health helps reduce it by 34.7%. In Shaanxi, weather helps prevent desertification, but poor soil conditions worsen it, showing how different factors affect different regions.
Research on desertification is complicated, and no single measure can explain all aspects. However, scientists predict that climate change will increase the amount of drylands on Earth, from 38% in the late 20th century to 50% or 56% by the end of the century, depending on how much the climate changes. These changes will likely affect areas like southwest North America, northern Africa, southern Africa, and Australia.
Drylands cover 41% of Earth's land and include 45% of the world's farmland. These areas are especially vulnerable to human activities and climate changes, which can lead to desertification. A 2020 study found that between 1982 and 2015, 6% of the world's drylands became more desert-like due to poor land use and climate change. Although Earth has seen more plant growth overall, climate change has worsened desertification in 12.6% of drylands, affecting 213 million people, most of whom live in developing countries.
Effects
There has been a 25% increase in dust released into the air worldwide each year since the late 1800s. Desertification has caused more loose sand and dust to be available for the wind to carry, which can create dust storms. For example, dust storms in the Middle East are becoming more common and stronger in recent years because less rainfall has reduced soil moisture and plant cover.
Dust storms can cause health problems such as pneumonia, asthma, and skin irritation. They can also pollute water sources, reduce the efficiency of clean energy, and stop most types of transportation.
Dust and sand storms can harm the climate, which can worsen desertification. Dust in the air reflects sunlight (Hassan, 2012). While dust may temporarily cool the ground, it can increase the temperature in the atmosphere. This can make clouds less stable and reduce rainfall.
Desertification is threatening global food supplies. As the world’s population grows, more food is needed. Farming is moving from one country to another. For example, Europe imports over 50% of its food. At the same time, 44% of farmland is in dry areas that produce 60% of the world’s food. Desertification is reducing the amount of land that can be used for farming, but food demand continues to rise. Soon, demand may outpace supply. Conflicts between herders and farmers in countries like Nigeria, Sudan, and Mali have worsened due to climate change, land degradation, and population growth.
At least 90% of people living in dry areas are in developing countries, where they often face poor economic and social conditions. Land degradation makes these problems worse because it lowers productivity, makes living conditions unstable, and limits access to resources.
Many underdeveloped countries face issues like overgrazing, soil exhaustion, and overuse of groundwater as they try to use dry areas for farming. Leaders are hesitant to invest in dry regions that have low farming potential. This lack of investment leaves these areas without development. When poor weather conditions, lack of infrastructure, limited market access, outdated farming methods, and a population with limited education and food supply are combined, these areas remain underdeveloped.
Desertification often makes rural land unable to support the same number of people who lived there before. This causes large numbers of people to leave rural areas and move to cities, especially in Africa, leading to unemployment and overcrowded slums. The number of environmental refugees is growing, with predictions that sub-Saharan Africa could have nearly 200 million refugees by 2050 instead of 14 million in 2010. This could create a crisis for the region, as nearby countries may not be able to support so many refugees.
In Mongolia, 90% of the land is fragile and dry, forcing many herders to move to cities for work. Herders who stay on the dry land use careful grazing methods to protect the land.
Agriculture is a major source of income for people in desert areas. However, desertification has damaged the land so much that farming is no longer productive or profitable in many regions. This has hurt local economies and increased poverty.
There is growing global effort, such as the UN SDG 15, to fight desertification and restore damaged land.
Geographic areas affected
Drylands cover about 40–41% of Earth's land and are home to more than 2 billion people. It is estimated that 10–20% of drylands are already degraded. The total area affected by desertification is between 6 and 12 million square kilometers. About 1–6% of dryland residents live in desertified areas, and a billion people are at risk of further desertification.
Climate change and human activities contribute to desertification, as seen in the Sahel region of Africa. This area has a dry, hot climate with high temperatures and low rainfall (100–600 mm per year). Droughts are common in the Sahel. Over the past 50 years, the region has lost about 650,000 km of productive agricultural land, and desertification has spread significantly.
The Sahara’s climate has changed greatly over the past few hundred thousand years, shifting between wet (grassland) and dry (desert) every 20,000 years. This change is linked to long-term climate cycles that affect the North African Monsoon, which is influenced by Earth’s axial tilt changes over 40,000 years. Since 1900, the Sahara has expanded 250 km to the south over a 6,000 km stretch of land.
Lake Chad, in the Sahel region, has dried up due to water use for irrigation and less rainfall. The lake has shrunk by over 90% since 1987, displacing millions of people. Recent efforts have helped restore the lake, but it remains at risk of disappearing.
To reduce desertification, the Great Green Wall initiative began in 2007. It involves planting vegetation along a 7,775 km, 15 km wide strip across 22 countries by 2030. The goal is to help the land retain water after rainfall, supporting land recovery and farming. Senegal has planted 50,000 acres of trees, improving land quality and creating economic opportunities.
The Gobi Desert, in northern China and southern Mongolia, is the fastest-growing desert. It turns 3,600 square kilometers of grassland into wasteland each year. Though the Gobi is far from Beijing, sand dunes have formed 70 km outside the city.
In Mongolia, 90% of grasslands are vulnerable to desertification, according to the UN. About 13% of desertification is caused by natural factors, while the rest results from human actions, such as overgrazing and soil erosion. From 1940 to 2015, Mongolia’s average temperature rose by 2.24°C, with the warmest decade being the most recent. Rainfall has decreased by 7%, increasing dryness. Over 70% of Mongolia’s land is degraded due to overgrazing, deforestation, and climate change. The government lists forest fires, blights, unsustainable forestry, and mining as major causes. Switching from sheep to goats for cashmere wool production has damaged grazing lands, as goats eat roots and flowers.
To help reduce desertification’s financial impact in Inner Mongolia, Bai Jingying teaches women traditional embroidery, which they sell to earn income.
The Gobi Desert is expanding rapidly into China, with 3,600 km of grassland lost yearly. Dust storms have increased between 1996 and 2016, harming agriculture. In some areas, desertification has slowed or reversed.
The boundaries between desert and grassland are constantly changing, mainly due to pre-growing season climate conditions that affect evaporation and plant growth.
The Gobi’s expansion is mostly due to human activities, such as deforestation, overgrazing, and water use, as well as climate change.
China has implemented plans to slow desert expansion, with some success. The Three-North Shelter Forest Program, started in 1978 and continuing until 2050, aims to reverse desertification by planting trees on 36.5 million hectares across northern China.
South America is also vulnerable to desertification. About 25% of its land is dryland, and over 68% has suffered soil erosion from deforestation and overgrazing. In Bolivia, Chile, Ecuador, and Peru, 27–43% of land is at risk of desertification. In Argentina, Mexico, and Paraguay, more than half of the land is degraded and cannot be used for farming. In Central America, drought has increased unemployment and reduced food security, leading to migration. Similar effects are seen in rural Mexico, where 1,000 km of land is lost yearly to desertification. In Argentina, desertification threatens the nation’s food supply.
Reversing desertification
There are ways to help stop or reverse desertification. Some of these methods face challenges, such as high costs or lack of support from leaders and funding. However, others only need people to use logical thinking to solve the problem.
One challenge is that the cost of using sustainable farming methods may be too high for some farmers, even though these methods help the environment and society. Another challenge is that leaders may not support land restoration programs, and there may not be enough money to fund these efforts.
Desertification is a serious threat to plant and animal life. Some countries have created plans to protect endangered species and their habitats.
Methods to fight desertification focus on two main areas: providing water and improving soil quality. Improving soil is often done by planting rows of trees, bushes, or small woodlots to reduce erosion and water loss.
Some types of soil, like clay, can become hard and compact when they lack water, unlike sandy soils. Techniques like zaï (a method of digging pits to hold water) or special farming methods are used to help grow crops in these conditions.
Another method is contour trenching. This involves digging long, deep trenches that follow the natural lines of the land. These trenches help hold water and prevent erosion. Stone walls are placed around the trenches to keep them open. This method was developed by Peter Westerveld.
Soil fertility can be restored by planting certain types of plants. Legumes, which add nitrogen to the soil, and plants like Opuntia (a type of cactus) help improve soil quality. Crops such as grains, barley, beans, and dates are also important. Sand fences can help control sand movement and erosion.
Another way to improve soil is by using nitrogen-rich fertilizers. However, these fertilizers are expensive, so many small farmers avoid using them, especially in areas where farming is done for personal use. Countries like India, Zambia, and Malawi have started offering financial help to farmers to use these fertilizers.
Some research centers are testing ways to help trees grow in dry areas by using fungi called mycorrhiza. These fungi attach to tree roots and help the trees absorb more nutrients from the soil.
Scientists have also studied ways to improve soil microbes, such as those that help plants make food from sunlight, to protect dry areas. The goal is to strengthen the natural relationship between microbes and plants.
Because there are many types of deserts, there are different methods to restore them. For example, salt flats in the Rub' al Khali desert in Saudi Arabia may be suitable for farming using seawater, without needing much fresh water or energy.
A method called Farmer-Managed Natural Regeneration (FMNR) has helped restore land in Niger. This method allows native trees to regrow by carefully cutting back shrubs. The leftover plant material is used as mulch to keep soil moist and reduce water loss. Trees that are spaced properly can also help crops grow better. A similar project in Ethiopia, supported by the World Bank, has helped restore land.
In 2012, the Food and Agriculture Organization of the United Nations started a program to share knowledge about restoring dry areas. In 2015, they published guidelines for restoring forests and land in dry regions, working with Turkey.
The "Green Wall of China" is a large project to stop desertification. It is similar to what American farmers did in the 1930s to stop the Dust Bowl. Started in the 1970s, the project plans to last until 2055. China has planted over 66 billion trees, reducing desert land by about 1,980 square kilometers each year. This has also reduced sandstorms by 20%. Inspired by China’s success, the United Nations is planning a similar "wall" in Africa near the Sahara Desert.
In 2007, the African Union began the Great Green Wall of Africa project to fight desertification in 20 countries. The wall is 8,000 kilometers long and has $8 billion in support. It has restored 36 million hectares of land and aims to restore 100 million hectares by 2030. The project has created jobs, with over 20,000 jobs in Nigeria alone.
Restored grasslands can store carbon from the air as plant material. Grazing animals usually eat grass, which limits its growth. A method to restore grasslands uses fences to divide land into small areas. Farmers move their animals between these areas to let the grass grow. Some say this could help store more carbon in the soil, but others argue it does not fully stop desertification.
In northern China, scientists suggest using agrivoltaic systems (combining solar panels with farming) to help restore deserts. A study in the Kubuqi Desert found that these systems improved soil quality and plant growth. Solar panels reduce soil temperature and water loss, and help protect plants from sand. A large project in Inner Mongolia plans to use these methods to fight desertification.
History
The most famous deserts in the world were created by natural processes that happened over many years. For much of this time, deserts expanded and shrank without being affected by human actions. Paleodeserts are large areas of sand that are no longer active because plants have stabilized them. Some of these areas are larger than today’s main deserts, such as the Sahara, which is the largest hot desert.
Historical records show that serious and widespread land damage in dry areas several centuries ago occurred in three main regions: the Mediterranean, the Mesopotamian Valley, and the Loess Plateau of China, where many people lived.
The earliest known discussion about this topic began after France colonized West Africa. At that time, the Comité d'Etudes asked for a study on "desséchement progressif," which means gradual drying, to learn about the past expansion of the Sahara Desert. The modern study of desertification started with research on the drought in the Sahel during the 1980s.