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Desertification - Sahel case study

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Desertification in the Sahel region is a pressing environmental issue with far-reaching consequences. In this article, we will explore the causes, effects, and potential solutions to combat desertification, using a case study from the Sahel region. By examining the unique challenges faced in this area, we can gain insights into the broader fight against desertification and the importance of sustainable land management practices. The Sahel is a semi-arid zone stretching from the Atlantic Ocean in West Africa to the Red Sea in the East, through northern Senegal, southern Mauritania, the great bend of the Niger River in Mali, Burkina Faso, southern Niger, northeastern Nigeria, south-central Chad, and into Sudan ( Brittanica ).

It is a biogeographical transition between the arid Sahara Desert to the North and the more humid savanna systems on its Southern side.

Desertification in the Sahel has increased over the last number of years. It has been increasingly impacted by desertification, especially during the second half of the twentieth century. The whole Sahel region in Africa has been affected by devastating droughts, bordering the Sahara Desert and the Savannas.

During this period, the Sahara desert area grew by roughly 10% , most of which in the Southward direction into the semi-arid steppes of the Sahel.

Understanding desertification in the Sahel

The Sahel region, stretching across Africa from the Atlantic Ocean to the Red Sea, is characterized by fragile ecosystems and vulnerable communities. The combination of climate change, overgrazing, deforestation , and improper agricultural practices has resulted in extensive land degradation and desertification. The consequences of desertification in the Sahel are severe, including food insecurity, loss of biodiversity, and displacement of communities.

in the region, for around 8 months of the year, the weather is dry. The rainy season only happens for a few short months and only produces around 4-8 inches of water. The population growth over the years has caused illegal farming to take place over the last few years and has resulted in major soil erosion and desertification to take place.

Examining a specific case study in the Sahel region sheds light on the complexities and impacts of desertification. In a particular community, unsustainable farming methods and drought have led to soil erosion and degradation. The once-fertile land has turned into arid, unproductive soil, forcing farmers to abandon their livelihoods and seek alternative means of survival. This case study highlights the urgent need for intervention and sustainable land management practices in the region.

Addressing the challenges

To combat desertification effectively, a multi-faceted approach is necessary. First and foremost, raising awareness about the issue and its consequences is crucial. Governments, NGOs, and local communities must collaborate to implement sustainable land management practices. This involves promoting agroforestry, conservation farming, and reforestation initiatives to restore degraded land and improve soil health. Additionally, supporting alternative income-generating activities and providing access to water resources can help alleviate pressure on the land and reduce vulnerability to drought.

Read more: Preventing desertification: Top 5 success stories

The impact of humans on the Sahel

The impact of humans on the Sahel region is a critical factor contributing to its current challenges and environmental changes. Human activities, including armed violence, climate change, deforestation, and overgrazing, have had significant consequences for both the ecosystem and the local communities. While the area of the Sahel region is already considered to be a dry place, the impact of the human population in the area has really affected how the area continues to evolve. Towns are popping up all over the place, and because of this, more land is being used than ever before. The ground that they are building their lives on quickly began to die and became extremely unhealthy for any type of growth. This has made headlines everywhere and even caught the attention of the United Nations. In 1994, the United Nations declared that June 17th would be known as the World Day to Combat Desertification and Drought. . This was a result of the large-scale droughts and famines that had been taking place and were at their height between 1968 and 1974.

In conclusion, the impact of humans on the Sahel is a multifaceted issue. The region faces a humanitarian crisis alongside security concerns, with climate change and human activities playing significant roles. Desertification caused by climate change, deforestation, and overgrazing has resulted in land degradation, loss of vegetation, and increased vulnerability to droughts and food insecurity. Implementing sustainable land management strategies is essential to mitigate the impact and promote the resilience of the Sahel's ecosystems and communities.

Droughts, grazing, and recharging aquifers

The Sahel’s natural climate cycles make it vulnerable to droughts throughout the year. But, during the second half of the twentieth century, the region also experienced significant increases in human population and resulting in increases in the exploitation of the lands through (cattle) grazing, wood- and bush consumption for firewood, and crop growth where possible.

These anthropogenic processes accelerated during the 1960s when relatively high rainfall amounts were recorded in the region for short periods of time, and grazing and agricultural expansion were promoted by the governments of the Sahel countries, seeing a good opportunity to use the region’s ecosystem for maximizing economic returns.

This resulted in the removal of large parts of the natural vegetation, including shrubs, grasses, and trees, and replacing them with crops and grass types that were suitable for (short-term) grazing.

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The world effort for the Sahel:

Natural aquifers, which were previously able to replenish their groundwater stocks during the natural climate cycles, were no longer able to do so, and the regions closest to the Sahara desert were increasingly desertified.

Removing the natural vegetation removed plant roots that bound the soil together, with over-exploitation by grazing eating away much of the grass.

Agricultural activity disrupted the natural system, forcing significant parts of the Sahel region to become dry and barren. Before the particularly bad famine of 1984, desertification was solely put down to climatic causes.

As the Sahel dries, the Sahara advances : and it is estimated to advance with a rate of 60 kilometres the Sahel lost and the Sahara desert gained per year. Human influence is an important factor in the Sahel’s desertification, but not all can be attributed to human behaviour, says Sumant Nigam, a climate scientist at the University of Maryland.

'There is an important anthropogenic influence there, but it is also being met with natural cycles of climate variability that add and subtract in different periods', Nigam said. 'Understanding both is important for both attribution and prediction.' Ecologists have been meeting all over the world to discuss the desertification of the Sahel at length. While many possible solutions have been proposed, a few goals have been established and are being worked on. The Food and Agricultural Organization of the United Nations has not become involved and is working to create a long-lasting impact on the Sahel Region. However, after the mid-1980s , human-caused contributions were identified and taken seriously by the United Nations and many non-governmental organizations. Severe and long-lasting droughts followed throughout the 1960s-1980s, and impacted the human settlements in the forms of famine and starvation, allowing the Sahara desert to continue to expand southward. As a result, a barren and waterless landscape has emerged, with the northernmost sections of the Sahel transformed into new sections of the Sahara Desert. Even though the levels of drought have decreased since the 1990s, other significant reductions in rainfall have been recorded in the region, including a severe drought in 2012. It is estimated that over 23 million people in the Sahel region are facing severe food insecurity in 2022, and the European Commission projects that the crisis will worsen further amidst rising social security struggles. Now, the goal is to see change take place by 2063, a year that seems far away but is a start in the efforts to rebuild the Sahel Region.

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Case Study: Sahel Desertification

What is desertification: It is the term used to describe the changing of semi arid (dry) areas into desert. It is severe in Sudan, Chad, Senegal and Burkina Faso

What are the causes:

Overcultivation: the land is continually used for crops and does not have time to recover eventually al the nutrients are depleted (taken out) and the ground eventually turns to dust.
Overgrazing: In some areas animals have eaten all the vegetation leaving bare soil.
Deforestation: Cutting down trees leaves soil open to erosion by wind and rain.
Climate Change: Decrease in rainfall and rise in temperatures causes vegetation to die

What is being done to solve the problem?

Over the past twelve years Oxfam has worked with local villagers in Yatenga (Burkina Faso) training them in the process of BUNDING. This is building lines of stones across a slope to stop water and soil running away. This method preserves the topsoil and has improved farming and food production in the village.

Burkina Faso - desertification

This video shows the Sahel region south of the Sahara is at risk of becoming desert. Elders in a village in Burkina Faso describe how the area has changed from a fertile area to a drought-prone near-desert. The area experiences a dry season which can last up to eight or nine months. During this time rivers dry up and people, animals and crops are jeopardised.

This video showcases the Sahel region

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Causes and Impacts of Land Degradation and Desertification: Case Study of the Sudan

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Environmental degradation has become a very serious problem in Africa since the Sahelian drought. It refers to the diminishment of local ecosystem or the biosphere as a whole due to human activity or the climate factors. Butana, in the north-eastern part of Sudan is known by many nomadic tribes as a good palatable grazing area during and after the rainy season. Rainfall plays a dominant role in the vegetation growth of the area. The goal of this study is to monitor the extent and severity of environmental degradation in relation to climate variability and change. The rainfall time series (1940–2004) for four weather stations were examined on monthly and annual bases to investigate any possible trends. The analysis of rainfall showed gradual decrease in the rainfall for the whole duration of the study at three out of the four stations. The progressive decline in the rainfall since late 1960s was significant and cannot be considered random for the northern part of the area. A significant increase in temperature, in autumn, is partly due to dry conditions observed since the late 1960s. Satellite image was used for routine natural resource monitoring and mapping land degradation. The Moving Standard Deviation Index (MSDI) increased considerably from 1987 to 2000 and the Bare Soil Index (BSI) for the degraded sites increased from 0–8 in 1987 to 32–40 in 2000. The BSI image difference indicated that the index increased between 14 and 43 over the 13 years. It is therefore, observed that different ecosystems in Butana area were subjected to various forms of site degradation, which led to sand encroachment, acceleration of dunes development and increased water erosion in the northern part of the area. The area has also, been subjected to vegetation cover transformation that made the pastures to deteriorate seriously in quality and quantity; however, in many parts of the area, the degradation is still reversible if land use and water point sites are organized.

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Table Of Contents

desertification , the process by which natural or human causes reduce the biological productivity of drylands (arid and semiarid lands). Declines in productivity may be the result of climate change , deforestation , overgrazing, poverty , political instability, unsustainable irrigation practices, or combinations of these factors. The concept does not refer to the physical expansion of existing deserts but rather to the various processes that threaten all dryland ecosystems , including deserts as well as grasslands and scrublands .

Slightly less than half of Earth’s ice-free land surface—approximately 52 million square km (about 20 million square miles)—is drylands, and these drylands cover some of the world’s poorest countries. The United Nations Environment Programme (UNEP) notes that desertification has affected 36 million square km (14 million square miles) of land and is a major international concern. According to the United Nations Convention to Combat Desertification , the lives of 250 million people are affected by desertification, and as many as 135 million people may be displaced by desertification by 2045, making it one of the most severe environmental challenges facing humanity.

Africa is the continent most affected by desertification, and one of the most obvious natural borders on the landmass is the southern edge of the Sahara desert . The countries that lie on the edge of the Sahara are among the poorest in the world, and they are subject to periodic droughts that devastate their peoples. African drylands (which include the Sahara, the Kalahari , and the grasslands of East Africa) span 20 million square km (about 7.7 million square miles), some 65 percent of the continent. One-third of Africa’s drylands are largely uninhabited arid deserts, while the remaining two-thirds support two-thirds of the continent’s burgeoning human population. As Africa’s population increases, the productivity of the land supporting this population declines. Some one-fifth of the irrigated cropland, three-fifths of the rain-fed cropland, and three-fourths of the rangeland have been at least moderately harmed by desertification.

In general, desertification is caused by variations in climate and by unsustainable land-management practices in dryland environments . By their very nature, arid and semiarid ecosystems are characterized by sparse or variable rainfall. Thus, climatic changes such as those that result in extended droughts can rapidly reduce the biological productivity of those ecosystems. Such changes may be temporary, lasting only a season, or they may persist over many years and decades. On the other hand, plants and animals are quick to take advantage of wetter periods, and productivity can rapidly increase during these times.

Chutes d'Ekom - a waterfall on the Nkam river in the rainforest near Melong, in the western highlands of Cameroon in Africa.

Since dryland environments are used for a variety of human purposes (such as agriculture , animal grazing, and fuelwood collection), the various activities undertaken in them can exacerbate the problem of desertification and bring about lasting changes to dryland ecosystems. In 1977, at the United Nations Conference on Desertification (UNCOD) in Nairobi , Kenya , representatives and delegates first contemplated the worldwide effects of desertification. The conference explored the causes and contributing factors and also possible local and regional solutions to the phenomenon. In addition, the delegates considered the varied consequences of desertification, such as crop failures or decreased yields in rain-fed farmland, the loss of perennial plant cover and thus loss of forage for livestock , reduced woody biomass and thus scarcity of fuelwood and building materials, a decrease in potable water stocks from reductions in surface water and groundwater flow, increased sand dune intrusion onto croplands and settlements, increased flooding due to rising sedimentation in rivers and lakes , and amplified air and water pollution from dust and sedimentation.

Four areas affected by desertification

To better understand how climatic changes and human activities contribute to the process of desertification, the consequences listed above can be grouped into four broad areas:

Irrigated croplands, whose soils are often degraded by the accumulation of salts .
Rain -fed croplands, which experience unreliable rainfall and wind-driven soil erosion .
Grazing lands, which are harmed by overgrazing, soil compaction , and erosion.
Dry woodlands, which are plagued by the overconsumption of fuelwood.

Nearly 2,750,000 square km (about 1,062,000 square miles) of croplands are irrigated. Over 60 percent of these irrigated areas occur in drylands. Certainly, some dryland areas have been irrigated for millennia, but other areas are more fragile. Of the irrigated dryland, 30 percent (an area roughly the size of Japan) is moderately to severely degraded, and this percentage is increasing.

The main cause of declining biological productivity in irrigated croplands is the accumulation of salts in the soil. There is an important difference between rainwater and the water used for dryland irrigation . Rainwater results from the condensation of water evaporated by sunlight . Essentially, rainwater is distilled seawater or lake water. In contrast, water used for irrigation is the result of runoff from precipitation . Runoff percolates through the soil, dissolving and collecting much of the salts it encounters, before finding its way into rivers or aquifers . When used to irrigate crops, runoff evaporates and leaves behind much of the salts that it collected. Irrigated crops need an average of 80 cm (about 30 inches) of water annually. These salts can build up in the soil unless additional water is used to flush them out. This process can rapidly transform productive land into relatively barren salt flats scattered with halophytes (plants adapted to high levels of salt in the soil).

Most salt-degraded cropland occurs in Asia and southwestern North America , which account for 75 and 15 percent of the worldwide total, respectively. In Asia, Iraq has lost over 70 percent of its irrigated land to salt accumulation. In Russia, much of the irrigated land located where the Volga River runs into the Caspian Sea may last only until the middle of the 21st century before the buildup of salts makes it virtually unusable. Such losses are not restricted to developing countries. In the United States , salt accumulation has lowered crop yields across more than 50,000 square km (19,000 square miles), an area that is about a quarter of the country’s irrigated land.

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Article Contents

Data analysis, causes and pathways of desertification, conclusions, references cited.

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Dynamic Causal Patterns of Desertification

Helmut J. Geist (email: [email protected] ) is executive director, of the LUCC (Land Use and Cover Change) International Project, University of Louvain, 1348 Louvain-la-Neuve, Belgium.

Eric F. Lambin (email: [email protected] ) is chair, of the LUCC (Land Use and Cover Change) International Project, University of Louvain, 1348 Louvain-la-Neuve, Belgium. Lambin is also a professor at the University of Louvain.

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Helmut J. Geist, Eric F. Lambin, Dynamic Causal Patterns of Desertification, BioScience , Volume 54, Issue 9, September 2004, Pages 817–829, https://doi.org/10.1641/0006-3568(2004)054[0817:DCPOD]2.0.CO;2

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Using a meta-analytical research design, we analyzed subnational case studies (n = 132) on the causes of dryland degradation, also referred to as desertification, to determine whether the proximate causes and underlying driving forces fall into any pattern and to identify mediating factors, feedback mechanisms, cross-scalar dynamics, and typical pathways of dryland ecosystem change. Our results show that desertification is driven by a limited suite of recurrent core variables, of which the most prominent at the underlying level are climatic factors, economic factors, institutions, national policies, population growth, and remote influences. At the proximate level, these factors drive cropland expansion, overgrazing, and infrastructure extension. Identifiable regional patterns of synergies among causal factors, in combination with feedback mechanisms and regional land-use and environmental histories, make up specific pathways of land change for each region and time period. Understanding these pathways is crucial for appropriate policy interventions, which have to be fine-tuned to the region-specific dynamic patterns associated with desertification.

The causes of dryland degradation, also referred to as desertification, remain controversial ( Helldén 1991 , Thomas 1997 , Lambin et al. 2001 ). Local- to national-scale studies demonstrate the importance and socioecological significance of the process, but land-cover change in dryland ecosystems is poorly documented at the global scale, and its causes are not fully understood ( Reynolds and Stafford Smith 2002 , Lambin et al. 2003 ). The most authoritative definition of desertification remains that of the Convention to Combat Desertification: “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities” ( UNEP 1994 ). The two major, mutually exclusive—and still unsatisfactory—explanations for desertification are single-factor causation and irreducible complexity. On the one hand, proponents of single-factor causation suggest various primary causes, such as growing populations in fragile semiarid ecosystems and irrational or unwise land management by nomadic pastoralists. Central to this understanding is the overworking of land by ever-increasing numbers of the rural poor. In its extreme form, the theory of single-factor causation leads to the notion of “man-made deserts” (i.e., the human-driven, irreversible extension of desert landforms and landscapes; Breckle et al. 2002 , Le Houérou 2002 ). On the other hand, desertification has been attributed to multiple causative factors that are specific to each locality, revealing no distinct pattern ( Dregne 2002 , Warren 2002 ). There is a great deal of debate, not only on whether the causes of desertification lie in the socioeconomic or biophysical sphere (human-induced land degradation versus climate-driven desiccation) but also on the degree to which these causes are local or remote, and on how variables interact across organizational levels in different regions of the world and at different time periods ( Pickup 1998 , Lambin et al. 2002 , Reynolds and Stafford Smith 2002 ).

In addition to chronicling the struggle to arrive at an agreed-upon understanding of the causes of desertification, the literature is rich in local case studies investigating the causes and processes of dryland change in specific localities. Our aim in this article is to preserve the descriptive richness of these local case studies while using them to generate a general understanding of the proximate causes and underlying driving forces of desertification, including cross-scalar interactions of causes and feedbacks. Proximate causes are human activities or immediate actions at the local level, such as cropland expansion, that originate from intended land use and directly affect dryland cover. Underlying driving forces are fundamental social and biophysical processes, such as human population dynamics or agricultural policies, that underpin the proximate causes and either operate at the local level or reflect influences at the national or global level. Mediating factors, such as wealth or access to resources, may shape or modify the interplay between these two broad groups of causative factors. Social and ecological responses to land-cover changes may create feedbacks that amplify or dampen land-use and land-cover change.

We identified typical pathways of dryland change, defined as particular chains of events and sequences of cause and effect resulting in specific outcomes of desertification. These outcomes include decreases in vegetation cover; exposure of bare, rocky ground; increases in sand cover; and salinization. Pathways are made up of initial conditions, causes, and feedbacks. The environmental and land-use history of each region defines the initial conditions for each subsequent round of land use and ecosystem change ( Foster et al. 2003 , Lambin et al. 2003 ).

We analyzed the frequency of proximate causes and underlying driving forces of desertification, including their interactions with one another and their feedbacks on land use, as reported in 132 subnational case studies. Our results show that desertification is driven by a limited suite of recurrent core variables, of which the most prominent at the underlying level are climatic factors, economic factors, institutions, national policies, population growth, and remote influences. At the proximate level, these factors drive the expansion of cropland (at the expense of grazing land and natural grassland, thus leading to overstocking) and infrastructure. Regional patterns of causal-factor synergies, in combination with feedback mechanisms and regional land-use and environmental histories, make up specific pathways of land change that can be identified for a given region and time period. Understanding these pathways of dryland change is crucial for designing appropriate policy interventions. To achieve sustainable management of dryland ecosystems, interventions have to be fine-tuned to the region-specific dynamic patterns associated with desertification ( Lambin et al. 2001 , 2003 ).

We analyzed case studies on the causes of desertification ( n = 132) to determine whether the proximate causes and underlying driving forces of dryland degradation fall into any pattern, using a configurational comparative research design ( Ragin 1989 , Matarazzo and Nijkamp 1997 ). This method of comparative meta-analytical research focuses on configurations of causally relevant characteristics of diverse, but substantively defined and intentionally selected cases that do not differ greatly from one each other with respect to the outcome that is being investigated (desertification). It aims at identifying cross-case pathways of causation by taking a middle way between qualitative case study and quantitative, variable-oriented research.

The study areas ranged from a small (1-hectare) site to a multiprovince area, and the cases spanned time periods from 1700 to 2000, with 1915 to 1994 being the mean period. The 132 cases of desertification were taken from 54 articles published in 28 journals covered by the citation index of the Institute for Scientific Information. We used five criteria for selecting case studies: (1) sites in human use (i.e., no “wilderness areas”); (2) in-depth field investigations; (3) consideration of clearly named factors as potential causes of desertification, including basic features of the socioeconomic setting and the natural resource endowment; (4) investigation methods that included quantitative data, particularly for assessing the rates of land change; and (5) absence of obvious disciplinary bias. We assumed that each study revealed the actual causes of desertification in the study area. Therefore, our comparative analysis of cases evaluates which causal patterns associated with desertification are most often found in different dryland regions of the world. The complete list of case studies and details of the method are given in Geist (2004) , including a discussion of the limitations of the meta-analysis. For example, using desertification as the sole search term in identifying case studies, and not other terms such as land degradation, may have led us to include relatively more severe cases of dryland degradation and relatively more authors who hold a more deterministic view of the issue. We may thus have excluded relatively more cases exhibiting the complex and nonequilibrium dynamics of coupled humanenvironmental systems.

We identified four broad clusters of proximate causes: agricultural activities, infrastructure extension, wood extraction (and related activities), and increased aridity. Each category of proximate causation was subdivided; for example, infrastructure extension included the extension of irrigation works, human settlements, and road networks, while agricultural activities were divided into livestock and crop production. Livestock production was further subdivided into nomadic grazing, extensive grazing, and intensive livestock production; crop production was subdivided into annual, perennial, and wetland or irrigation cropping. Underlying driving forces were grouped in six broad clusters of factors (climatic, demographic, policy or institutional, economic, technological, and cultural or sociopolitical). Each category was subdivided into specific factors; for example, cultural or sociopolitical factors were partitioned into (a) public attitudes, values, and beliefs and (b) individual and household behavior ( figure 1 ; Turner et al. 1995 , Nicholson 2002 , Lambin et al. 2003 , Mooney et al. 2003 ).

Causal factors were quantified by determining the most frequent proximate and underlying factors reported in the case studies. The major interactions and feedback processes among these factors were also identified to reveal the system dynamics that commonly lead to desertification. Three modes of causation were distinguished: single-factor causation (one individual underlying factor driving one or more proximate factors), chain-logical causation (several interlinked factors in combination, leading to desertification), and concomitant occurrence (independent, separate operation of factors causing desertification). Results were broken down by broad geographical dryland regions ( Middleton and Thomas 1997 , Reynolds and Stafford Smith 2002 ). Dryland cases from Asia ( n = 51) stemmed from the Central Asian desert and steppe region, the East Mediterranean steppe zone, the Arabian Peninsula, and the Thar Desert in India. African cases ( n = 42) originated from the Sahelian and Sudano-Sahelian zones of West Africa, the western Mediterranean Basin (North Africa), the East African grassland zone, and the Kalahari steppe in southern Africa. European dryland cases stemmed exclusively from the northern Mediterranean basin ( n = 13) and Australian cases from the central part of the continent ( n = 6). In the United States and Latin America, cases originated from the US Southwest ( n = 6) and from Latin American sites ( n = 14) in Mexico and Patagonia. A causative factor, or factor combination, was called “robust” if it showed little regional variation across major dryland regions.

Sites under study fell into a wide range of initial ecological and climatic conditions. Annual rainfall ranged from less than 50 millimeters (mm) in hyperarid basins or plains to more than 500 mm in subhumid mountain sites. Some sites were characterized by a uniform permafrost soil or fossil sand dune coverage, while others featured loamy, loessial, sandy, skeletal (gravel, stone-mantled), or clay soils. At some sites, the area of eroded, bare, rocky ground cover increased gradually, at an annual rate of about 1%, while at other sites it increased far more rapidly ( Geist 2004 ).

Tables 1 through 4 list the proximate causes and underlying driving forces of desertification, broken down by broad geographical regions or subcontinents. They show the frequency of each causative variable reported in the case studies, both as an absolute number and as a relative percentage. Results are given in order of decreasing importance; factors that occurred in less than 25% of the cases are not reported. Tables 1 and 3 give only the broad clusters of proximate causes and underlying driving forces; tables 2 and 4 provide a detailed breakdown of these broad clusters into specific factors.

Proximate causes.

At the proximate level, desertification is best explained by the combination of multiple and coupled social and biophysical factors rather than by single variables. Dominating the broad clusters of proximate factors is the combination of agricultural activities, increased aridity, extension of infrastructure, and wood extraction (or related extractional activities), with clear regional variations. In particular, agricultural activities and increased aridity form a robust combination, although one that often occurs with other proximate causes (table 1) .

Agricultural activities or agrarian land uses are the leading proximate cause associated with nearly all cases of desertification (95%). They include extensive grazing, nomadic grazing (pastoralism), and annual cropping (table 2) . Extensive livestock production, carried out under the mode of either sedentary or transhumant (seasonal nomadic) husbandry, displays low geographical variation as a cause of desertification. In contrast, activities of pastoral nomadic groups feature exclusively Asian and African cases and are reported as causing desertification only half as often as extensive grazing. Livestock production slightly outweighs crop production as a cause of desertification, but both activities remain intricately interlinked in most cases. The exceptions are the US Southwest, Latin America (Patagonia), and the Australian drylands, where cropping is of little or no importance, either as land use or as a cause of desertification. In most cases, agricultural expansion into marginal rangeland areas during wet periods leaves farmers more seriously exposed to hazard when drought returns than pastoralists would have been ( Glantz 1994 ). In fact, sedentary annual cropping is reported three times more frequently as a cause of desertification (44%) than other modes of cropping, such as wetland farming or cultivation of perennials (15% for all regions). In other cases, cropland expansion on areas previously used for pastoral activities leads to overstocking on the remaining, reduced rangeland, triggering soil degradation at sites that are not suitable for permanent agriculture.

Increased aridity is a robust proximate cause of desertification, both indirectly through greater rainfall variability and directly through prolonged droughts. Not only decreased annual precipitation but also warmer climate conditions, in combination with extreme weather events (attributed by several authors to global climate change), are chiefly characteristic of Asia. Among the other effects of increased aridity on land cover are changes in fire regimes (mainly increased fire frequencies) and greater soil erosion triggered by more frequent oscillations between warmer, drier conditions and cooler, more humid conditions. However, these effects are reported as causes of desertification only one-third as often as prolonged drought periods.

The extension of infrastructure associated with desertification is frequent mainly in cases from Asia, Africa, and Australia. Desertification is most often linked to the development of water-related infrastructure for cropland irrigation and pasture development (reservoirs, dams, canals, boreholes, and pump stations), leading to a decrease in livestock mobility ( Niamir-Fuller 1999 ). In Asia and Africa, the buildup of irrigation infrastructure is associated with expanding human settlements, following an increase in food production and food security. Other infrastructure components, such as road extension, oil and gas industry facilities, mining, and quarrying, are far less frequently reported. The extraction of wood (fuelwood, pole wood, charcoal) from forests and woodlands is reported to influence desertification in less than half of the cases.

Among the detailed categories of proximate causes of dryland degradation for all regions, the combination of extensive livestock production, increased aridity, production of annual crops, and water-technology extension stands out. Contrary to widely held views, the evidence of these case studies suggests that overstocking is not the primary cause of desertification, but happens when cropland expands onto rangelands. The evidence also suggests that nomadic pastoralism and households' harvesting of fuelwood for domestic purposes are not the only major agents of dryland degradation.

Underlying driving forces.

At the underlying level, desertification is best explained by regionally distinct combinations of multiple, coupled social and biophysical factors and drivers acting synergistically, rather than by single-factor causation. In more than half of the cases, desertification was driven by the interplay of four to six factors (table 3) . A recurrent and robust combination of driving forces—though differing widely in the range of specific factors involved—includes climatic factors leading to reduced rainfall, agricultural growth policies, newly introduced land-use technologies, and land-tenure arrangements that are no longer suited to contemporary dryland ecosystem management.

Climatic factors, mainly associated with a decrease in rainfall (reduced by as much as 1.5% annually over the last quarter of the 20th century in southern Africa), are prominent underlying driving forces of desertification (86%). They operate either indirectly, through changes in land use resulting from variation in rainfall (during dry years, annual precipitation deviates from the long-term average by as much as 80% at some locations in the western Kalahari steppe), or directly, affecting land cover in the form of prolonged droughts (such as the 1960–1990 period in semiarid parts of the Sudan, with the length of the wet season contracting by 1.5% on average per year). Although more than one-third of the studies mention climatic influences but fail to explicitly describe them, the most widespread mode of causation is reported to be climatic conditions operating concomitantly or synergistically with socioeconomic driving forces, such as technological changes (42%; table 4 ). Meteorological conditions are also part of feedback loops related to desertification (discussed below).

In many cases (69%), technological factors are robust drivers of desertification (table 4) . Most strikingly, technological innovations are reported to be associated with desertification as frequently as are deficiencies of technological applications. Innovations mainly comprise improvements in land and water management through motor pumps and boreholes (at the village level) or through the construction of hydrotechnical installations such as dams, reservoirs, canals, collectors, and artificial drainage networks (for large-scale irrigation schemes). When applied, these developments are often coupled with high water losses due to poor maintenance of the infrastructure, especially in the Asian studies. In addition, they easily induce fundamental and often irreversible changes to the natural hydrographic network, altering hydrological cycles in most cases. The disaster of the Aral Sea is an extreme case of such perturbations ( Saiko and Zonn 2000 ). Technological applications associated with desertification also include transport and earthmoving techniques (trucks, tractors, caterpillar-tracked vehicles) and new processing and storage technologies (refrigeration containers on ships and trucks). These innovations can trigger rapid increases in production at remote sites (e.g., greater numbers of irrigated garden products or herds of sheep, both destined for distant markets). We note that some research, especially in Asia, is devoted to technologies that might be used to stabilize the sand that is threatening expensive highway, railroad, and irrigation infrastructure. Thus, technology also makes it possible to mitigate some of the adverse impacts of desertification.

Among the institutional and policy factors that underlie 65% of the reported cases of desertification, modern policies and institutions are as much involved as are traditional institutions (table 4) . Growth-oriented agricultural policies, including measures such as land distribution and redistribution, agrarian reforms, modern sector development projects, diffusion of agricultural intensification methods, and market liberalization policies, are as important in driving desertification as are institutional aspects of traditional land tenure, such as equal sharing of land and splintering of herds because of traditional succession law. Both traditional and modern institutions and policies thus reduce flexibility in management and increase the pressure on constant land units. The introduction of new land tenure systems, whether under private (individual) or state (collective) management, is another important factor associated with desertification. There are distinct regional variations in these factors, and the impact of policy is comparatively low in the dryland areas of Europe and North America, where agriculture is only a minor sector of the national economy.

Economic factors (60%; table 4 ) are reported to underlie desertification in the form of a mixture of “boom” and “bust” factors, with considerable regional variations. Boom factors relate to market growth and commercialization, mainly entailing export-oriented market production, industrialization, and urbanization. Farmers respond to market signals reflecting high external demands for cotton, beef, and grain, with land increasingly put under rain-fed or irrigated production. Bust factors relate to the overuse of land because of land scarcity, low investments, low labor availability, indebtedness, lack of employment in the formal nonagrarian sector, or poverty. In dryland zones of Asia, cases of desertification are mainly driven by remote influences such as urbanization and commercialization. In many cases from Australia and Latin America, local farmers' response to an unfavorable economic situation, coupled with cycles of low rainfall, is reported to underlie desertification: Declining prices in the export-oriented sheep sector cause farmers to go into debt when their farms are no longer economically viable, inducing the overuse of scarce natural resources, especially during droughts.

Demographic factors (55%) show distinct regional clustering, with Asian and African cases of desertification most commonly cited as reflecting human population dynamics (table 4) . Most widespread are cases in which population growth, overpopulation, or population pressure is reported as a driver of desertification. The growth or increased economic influence of urban population often triggers migration of poor cultivators or herders from high-potential, periurban zones into marginal dryland sites. Consequently, the sometimes rapid increases in the size of local human populations are often linked to the immigration of cultivators into rangelands or regions with large-scale irrigation schemes, or of herders into hitherto unused, marginal sites, resulting in rising population densities there. Unexpectedly, the case studies reveal that population increase due to high fertility rates of impoverished rural groups, at a local scale and over a time period of few decades, is not a primary driver of desertification; it is reported to intervene in only 3% of the cases.

Prominent examples of migration-driven desertification stem from ancient or historical irrigation (oasis) sites in Central Asia, such as the Tarim and Hei River basins or the Aral Sea region. Until recently, traditional irrigation-farming practices in these regions had a relatively small impact on dryland ecosystems. Only in the second half of the 20th century did advances in hydrotechnical infrastructure synergize with population influx from remote zones and with outside economic demands such as attaining national self-sufficiency in clothing and food. Cotton monocultures and irrigated food crops (e.g., grain, rice, vegetables, fruits, grapevines), which are water-demanding, became key crops in areas of rapid settlement. In the period 1949–1985 alone, population in the Hei River basin almost doubled, from 55 million to 105 million people, with the total irrigated area tripling from 8 million to 24 million hectares and the number of reservoirs increasing from 2 to 95 in the same period of time ( Genxu and Guodong 1999 ). Often the state-driven opening up of oil or gas industries, mining activities, or power plants adds to the pressures on water resources stemming from growing population and agriculture.

Among cultural or sociopolitical factors (42%; table 4 ), public attitudes, values, and beliefs are as frequently associated with cases of desertification as is individual or household behavior, but there are regional variations. In Asia, land-use change leading to desertification is reported to be strongly driven by government encouragement of a frontier mentality (such as the official support for land consolidation in the northwestern territories of China) and by efforts to improve living standards and attain self-sufficiency in food. Such land-use change is very often linked to the belief that water is a “free good” and that grazing is “inefficient” when compared with grain production. Contrasting with this pattern are the Latin American cases, in which desertification seems to be predominantly driven by the individual responses or motivations of ranchers, and the Australian cases, in which a frontier mentality is not explicitly promoted by the state but seems to reflect a private attitude. War, insurgency, and violent conflicts over land lead to the disruption of land management, and thus to land degradation, in 8% of the cases.

Factor interactions.

Desertification usually results from interactions among multiple causal factors. In most cases, three to five underlying causes drive two to three proximate causes. A frequent pattern of causal interactions, driven mostly by policy, economic, and technological factors, stems from the creation of water-related infrastructure that results in the expansion of irrigated croplands and pastures ( Pickup 1998 , Genxu and Guodong 1999 , Saiko and Zonn 2000 , Dube and Pickup 2001 , Lin et al. 2001 ). Typically, new irrigation infrastructure prompts farmworkers to migrate into dryland areas, and it often stirs commercial and industrial developments as well as the growth of human settlements and related service economies. New irrigation infrastructure is often part of a larger infrastructure development related to regional economic growth. Commonly, road extension and the availability of earthmoving equipment for dam construction pave the way for the subsequent extension of irrigation and for urban or semiurban land uses. Underlying these proximate factors in the developing world are national policies aimed at consolidating territorial control over remote, marginal areas and attaining self-sufficiency in food and clothing. Rice and cotton are the key irrigated crops in dryland zones worldwide.

Paramount examples of desertification resulting from irrigation schemes are found in dry, hot river and lake basin ecosystems worldwide, with annual rainfall in the range of 30 to 300 mm and average summer temperatures at 23 degrees Celsius (°C) to 31°C. In Central Asia, the establishment during the second half of the 20th century of large hydrotechnical installations with low water-use efficiency disrupted fragile hydrographic ecosystems that had sustained flexible nomadic grazing or small-scale, settled oasis farming for centuries or even millennia. Consequently, severe and partly irreversible water degradation (salinization, drop in water tables, reduced volume of discharge), soil and vegetation degradation, and even “sandification” (the encroachment of sand into cultivated land through the activation of fixed or semifixed dunes) are reported from the Aral and Caspian Sea regions ( Saiko and Zonn 2000 , Kharin 2003 ) and the Hei and Tarim River basins ( Genxu and Guodong 1999 , Lin et al. 2001 ). Similar problems are found in Africa, in the Senegal River basin ( Venema et al. 1997 ).

Artificial watering points and roads can lead to expanding pastures and livestock populations (mainly cattle and sheep) and thus to desertification. Paramount examples of this pattern are found in major rangeland zones such as the East African grasslands, Kalahari steppe, and diverse rangeland ecosystems of Patagonia and Australia ( Keya 1998 , Pickup 1998 , Aagesen 2000 , Dube and Pickup 2001 ). Another pattern, seen mostly in the African Sudano-Sahelian zone, in East Africa, and in northern China, comes from growth-oriented development policies that favor cropping at the expense of herding ( Mwalyosi 1992 , Turner 1999 , Runnström 2000 ). The changing opportunities created by markets and policies often involve the introduction of new, mostly private land tenure in conjunction with zoning (e.g., into grazing or irrigation districts and reserved land). Outside policy interventions, such as newly introduced development projects, and the growth of agricultural commercialization send powerful market signals to local farmers. Customary land-management institutions, such as inherited succession law or flexible common-property regulations, conflict with the new requirements. In herding, labor investments are low and livestock mobility is restricted, thus triggering overstocking on the few remaining pastures. In cropping, inappropriate or unwise land management is practiced. This may include the undue extension of cereal crops onto marginal lands, despite high rainfall variability and the suitability of these marginal lands only for mobile grazing. Uncertain land tenure may arise from the overlapping of conflicting property-rights regimes, often leading to violent conflicts about land and thus reducing the adaptive capacity of herding and farming populations. In Asia and Africa, rapidly growing local population densities interact with other driving forces underpinning the proximate causes of desertification.

Mediating factors and cross-scalar interactions.

Some factors intervene in the interplay of underlying driving forces and proximate causes, and not all causative factors are important at the same hierarchical level of organization. Ethnic affiliation, access to resources such as cattle and land, and the type of land management practiced (e.g., monoculture versus agroforestry, small-scale versus large-scale) act as mediating or shaping factors in dynamic patterns of desertification. The impoverished conditions of land managers are the most important and robust mediating factors, increasing their vulnerability to dryland degradation (such as drought-induced crop failures and livestock decimation). In cases reported in Asia, Africa, Latin America, and Australia, economically deprived local farmers overuse their limited farmland in an effort to make ends meet. They do so either through continuous cultivation that leads to soil nutrient depletion or through year-round grazing that diminishes forage productivity and triggers the exposure of bare, eroded ground cover. In the latter half of the 20th century, the area of undegraded vegetation cover at sites in northwestern China (e.g., Populus euphratica ) and northern Burkina Faso was reduced at maximum annual rates of 3%–4% and 5%–6%, respectively, while the area of degraded vegetation cover increased at average annual rates of more than 4%.

Although proximate causes are linked to local scales, cross-scalar interactions of underlying factors are more frequently found than causative factors operating at individual scales (table 5) . Driving forces originating from an individual scale reportedly matter in 10% to 35% of the case studies (with local factors at the farm, household, community, or small-ecosystem levels outweighing the importance of upper-level factors). Interactions among driving forces from multiple scales dominate, with 30% to 80% of the studies reporting such cross-scalar interactions; the interplay between causes at the local and national levels is the most important. Global driving forces were less frequently mentioned in the desertification case studies than they were in case studies of tropical deforestation ( Geist and Lambin 2002 , Lambin and Geist 2003 ).

The evidence of the case studies suggests that, among causative factors, more positive feedback loops are at work that amplify desertification than negative feedbacks that could attenuate the process. Desertification thus leads to a vicious circle of resource degradation and impoverishment. One robust mechanism is a self-perpetuating process that involves expansion of cropland and grazing land, leading to soil degradation and overstocking in dryland areas affected by erratic rainfall fluctuations. Given a sustained demand for more land to be put under production, land degradation leads to further expansion of cultivated land or to further overuse of the land already under cultivation. In many cases from Asia and Africa, the development of grazing land (e.g., through improved grass varieties and aerial seed) does not happen in isolation, but is nearly always accompanied by the encroachment of crops onto rangelands. Thus, most improvements to grazing land do not result in a development for the better, because overstocking occurs on the shrinking rangelands ( Mwalyosi 1992 , Manzano et al. 2000 ).

Another positive feedback loop, which is most common in Africa and Asia, links rainfall deficit and high rainfall variability with land-use changes (agriculture, wood extraction, water-use schemes), accelerating land degradation ( Dube and Pickup 2001 , Zhou et al. 2002 ). A local variant of this mechanism, found in Africa, is a biophysical feedback loop that links land degradation (triggered by land-use change), changes in albedo and evapotranspiration, and decreases in precipitation, amplifying the impact of human activities on land cover ( Zeng et al. 1999 , Taylor et al. 2002 ). Another variant relates to hydrological stress and the process of degradation itself, which lead to an increase in the spatial heterogeneity of vegetation cover ( Schlesinger et al. 1990 , Seixas 2000 ). Linked to this feedback mechanism are changes in floristic composition, mainly of shrubs, and a shift toward woody species that are less palatable for livestock, further increasing the need for land to be put under production ( Brown et al. 1997 , Keya 1998 ).

Regional pathways of desertification.

Dominant causative factors and feedbacks, combined with environmental and land-use histories, allow the identification of typical regional pathways of desertification. In Central Asia, notably northern China, the most spectacular outcome of desertification is a widespread increase in desertlike sand cover, which is linked to the exceptionally strong impact of socioeconomic driving forces such as centrally planned frontier colonization and (sometimes forced) population movements ( Jiang 2002 , Sneath 2002 ). But the spread of sand cover is also linked to the region's predominantly sandy soils and loess formations and to the geological and climatic predisposition for desert formation of vast basins and plateaus. In ancient times, under various dynasties, climatic variations and destructive land uses operated in causal synergy to expand the oscillating desert margins, resulting in a sandy, desiccated landscape with the highest rates of dryland degradation worldwide. Two central pathways of partly irreversible desertification in Central Asia are the invasion of grain farming into steppe grazing land, triggering soil degradation as well as overstocking, and of large-scale hydraulic cultures into desert ecosystems that historically supported only localized, traditional oasis farming ( Zhou et al. 2002 , Kharin 2003 ).

In contrast, a typically African pathway of desertification involves the spatial concentration of pastoralists (as a result of the shift from a nomadic to a sedentary way of life) and farmers around infrastructure nuclei. This local concentration of population results in overgrazing, extensive fuelwood collection, and high cropping intensities, ultimately leading to degraded vegetation and declining soil productivity during periods of drought ( Mwalyosi 1992 , Dube and Pickup 2001 ).

“Beefing up” of fragile dryland ecosystems, with little or no involvement of cropping, frequently characterizes the desertification pathways of Australia and of North and South America. Historically, these rangeland zones typically shared common patterns of land use, such as the rapid introduction by European settlers of exotic livestock species and commercial pastoralism into ecosystems that had not undergone these uses before. Since about the 1950s, however, the cost-price squeeze affecting agriculture in industrialized countries has led to different variants of this trajectory. In Australia, the livestock industry and its complex of related infrastructure developed sufficient flexibility to counterbalance droughts and avoid spectacular desertification ( Pickup 1998 ). In the US Southwest, principal land uses shifted away from cattle ranching to meet urban-driven aspirations ( Fredrickson et al. 1998 ). In both areas, dryland-cover change happened episodically and was linked to shifts in rainfall and land use. Rates of desertification reached historical peaks in the late 19th and early 20th centuries but have largely subsided since then. Patagonia and northern Mexico, by contrast, suffered from a lack of advanced technologies to deal with the vagaries of oscillating natural resource productivity and, in general, from a lack of alternative land uses or diversification options. Local farmers were forced to continue raising livestock, sometimes under conditions of impoverishment and deprivation. Consequently, dryland degradation in these areas is not just a historical phenomenon, but continues to advance ( del Valle et al. 1998 , Manzano et al. 2000 ).

Another common trajectory of dryland change is found in the Mediterranean basin of southern Europe. A millennia-old tradition of agropastoral land use has removed nearly all forest cover but has favored a highly resilient phrygana (shrub) vegetation, reflecting various stages of soil degradation. The still-valuable agricultural base is at risk only when the mechanization of farming on skeletal soils induces further soil erosion, or when grazing on remote mountain ranges is followed by devastating fires ( Margaris et al. 1996 , Kosmas et al. 2000 ).

Our meta-analysis does not provide support for either of the two large groups of explanations for dryland degradation ( Watts 1985 , Helldén 1991 , Thomas 1997 ). Our results do not reflect irreducible complexity ( Dregne 2002 , Warren 2002 ); on the contrary, they reveal distinct patterns. Nor do they identify a single cause responsible for an irreversible extension of desert landforms and landscapes ( Breckle et al. 2002 , Le Houérou 2002 ), be it irrational land management by nomadic pastoralists, growing population, macroeconomic forces, unjust class and power relations, or climatic factors. Rather, we identified multiplicity as the most common theme reported: multiple agents; multiple uses of land; multiple responses to social, climatic, and ecological changes; multiple spatial and temporal scales in the causes of and responses to desertification; multiple connections in social and geographical space; and multiple ties between people and land in dryland areas ( Rindfuss et al. 2003 ). The theoretical framework that best accounts for this complexity is system dynamics ( Lambin et al. 2003 ), with special emphasis on the history (initial conditions) and adaptation of the system, the heterogeneity of the actors, the hierarchical levels of organization, and the nonlinear dynamics caused by feedback mechanisms. It is important to note that this complexity is associated with a limited number of recurrent pathways of desertification, which makes the problem tractable ( Reynolds and Stafford Smith 2002 ).

Most of the case studies of desertification report variants of a general syndrome that derives from resource scarcity and leads to a gradual pressure of production on resources ( Mooney et al. 2003 , Geist 2004 ). These studies report an increased intensity (per unit area) of rural labor investment and other artificial investments, such as watering infrastructure, to increase the production of land. The proximate factors related to this syndrome include the addition of new and more livestock species ( Keya 1998 ), year-round grazing ( Aagesen 2000 ), increased soil preparation through ploughing and continuous cropping ( Mwalyosi 1992 , Kosmas et al. 2000 ), and increased diversion of artificially gained water onto marginal land ( Genxu and Guodong 1999 ). Most of these factors involve greater input commitments per unit land area compared with traditional dryland uses ( Margaris et al. 1996 , Niamir-Fuller 1999 ) such as nomadic pastoralism or shifting cultivation. Could it be that the final link in the causal chain tying social to environmental change is land-use intensification in dryland ecosystems that had been immune from such land uses before, thus increasing these ecosystems' vulnerability to dry episodes ( Pickup 1998 , Manzano et al. 2000 , Lin et al. 2001 , Kharin 2003 )? Some cases seem to show that intensive land use may follow from production pressure on a fluctuating resource base, but that such intensive land use does not necessarily lead to desertification ( Rasmussen et al. 2001 ). There are examples of integrated animal husbandry and cropping systems in West Africa ( Mortimore et al. 1999 ) but also of land abandonment and disinvestment in labor in southern Europe ( Kosmas et al. 2000 ). A critical point is that pressures derive not only from changes in the intensity and magnitude of resource extraction but also from the way that resources are extracted ( Watts 1985 , Turner 1999 ). This suggests that future case studies should strive for a better understanding of the material reality of land use, which is shaped not only by an oscillating resource base (rainfall, biomass) ( Zeng et al. 1999 , Seixas 2000 , Nicholson 2002 ) but also by labor processes ( Turner 1999 , Fernandez et al. 2002 ) and the social relations of livestock production and farming operations over time ( Rasmussen et al. 2001 , Zhou et al. 2002 ). In particular, a more nuanced population analysis is needed ( Lambin et al. 2003 ).

Another recurrent theme in desertification case studies is that sociocultural changes have modified the adaptive strategies of dryland societies in the face of natural variability (which is inherent to dryland ecosystems) and have therefore reduced the resilience of socioecological systems, creating instability. In traditional rural societies, land productivity has often been multiply constrained, and cultural organizations have been adapted to episodic but recurrent changes. In the West African Sudan-Sahel, for example, land productivity is linked to oscillating rainfall and constrained by a nested system of seasonally differentiated rights to use each piece of land, distributed among various sedentary farming and pastoral groups (households, lineages, villages, groups of settlements, pastoral clans) ( Turner 1999 ). During periods of drought, modifications of land management have been negotiated among all of these groups. Adaptation requires a high degree of flexibility and cooperation in the highly mobile grazing systems practiced by nomads ( Niamir-Fuller 1999 ). In modern societies, cultural change becomes directional rather than cyclical, because land users as well as investors and consumers of agricultural produce embrace the promise of progress, particularly in technology and material well-being ( Fernandez et al. 2002 , Jiang 2002 ). In many cases, we found strong directionality manifested in land-use intensification, which could be interpreted as an increasing tendency to view the environment as a medium for rapid material or economic gains. With the shift from traditional to modern rural societies, cultural change brings about a directional transformation of the environment as well. In a few cases from the Sudan-Sahel in which land productivity has continued to be multiply constrained, rates of dryland degradation are low to nil. In some instances, highly intensive agrosilvopastoral production systems, developed under semiarid conditions, have been able to mitigate the vagaries of natural climatic fluctuations, markets, and even population pressure. Data from some densely populated village areas in the Kano close-settled zone of northeastern Nigeria, for example, suggest that the transformation of woodland or shrubland into farmland not only added economic value to farming but also led to an increase of plant biomass on farmed parkland as well as high livestock densities on crop residues ( Mortimore et al. 1999 ).

Our meta-analysis of case studies found that the relative weight and particular sequence of causes of desertification vary from region to region. The results highlight the interplay of proximate causes and underlying driving forces, both socioeconomic and biophysical, in the processes of desertification. Our analysis also revealed more complex dynamic patterns of dryland degradation, given the importance of mediating factors, feedback loops, and initial conditions. These elements make it possible to identify regional pathways of dryland change. This illuminates the causative mechanisms of desertification far more than previous compilations of causes, which were often static, did not differentiate between proximate and fundamental causes, and failed to trace the pathways connecting various causes in a structured way. Our analysis suggests that claims that desertification is either a human-made or a purely natural (i.e., climate-driven) process should be more nuanced. Indeed, case studies indicate that desertification is a coupled biophysical and socioeconomic process ( Puigdefábregas 1998 , Reynolds and Stafford Smith 2002 ), the details of which need to be specified for the various regions affected by desertification.

Evidence from empirical case studies that identify both proximate causes and underlying forces of desertification shows that dryland degradation—with desertification as a potential but not necessary outcome—is determined by different combinations of proximate causes and underlying driving forces in varying geographical contexts. Nearly all of these combinations include coupled socioeconomic and biophysical factors. Some of the combinations are geographically robust (such as the spread of watering and related infrastructure driven by growth-oriented policies and economic demands, which in turn are stirred by demographic changes), but most of them are region and time specific.

The observed causal-factor synergies and pathways of dryland change challenge single-factor explanations that put most of the blame for desertification on the overworking of land by increasing numbers of rural poor and by nomadic populations. Rather, our analysis reveals that, at the underlying level, public and individual decisions largely respond to national-scale policies promoting advanced land-use technologies and creating new economic opportunities. These responses are mediated by land-tenure systems and other local-scale institutions. Our analysis further reveals that, at the proximate level, regionally distinct modes of increased aridity, expansion of cropping and grazing activities, infrastructure extension, and, to a lesser degree, wood extraction prevail in causing desertification. Two major implications of this evidence are, first, that no global set of indicators to assess desertification status could reveal the complexity of human-environment systems inherent to dryland change, and second, that no universal policy for mitigating desertification can be conceived for all the dryland areas of the globe. Rather, a detailed understanding of the complex set of proximate causes and underlying driving forces affecting dryland-cover change in a given location is required before any assessment and policy intervention.

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Frequency of broad clusters of proximate causes in desertification, by number and relative percentage.

Frequency of specific proximate causes in desertification, by number and relative percentage.

Frequency of broad underlying driving forces in desertification, by number and relative percentage.

Frequency of specific underlying driving forces in desertification, by number and relative percentage.

Driving forces of desertification, by scale of influence.

Causes of desertification. Six broad clusters of underlying driving forces (fundamental social or biophysical processes) underpin the proximate causes of desertification, which are immediate human or biophysical actions with a direct impact on dryland cover.

Author notes

Month:	Total Views:
November 2016	1
December 2016	1
January 2017	50
February 2017	68
March 2017	67
April 2017	62
May 2017	46
June 2017	36
July 2017	24
August 2017	25
September 2017	54
October 2017	30
November 2017	80
December 2017	157
January 2018	124
February 2018	186
March 2018	177
April 2018	212
May 2018	200
June 2018	94
July 2018	120
August 2018	183
September 2018	143
October 2018	205
November 2018	297
December 2018	221
January 2019	172
February 2019	176
March 2019	243
April 2019	317
May 2019	303
June 2019	143
July 2019	147
August 2019	172
September 2019	234
October 2019	286
November 2019	252
December 2019	144
January 2020	184
February 2020	211
March 2020	240
April 2020	257
May 2020	161
June 2020	167
July 2020	131
August 2020	119
September 2020	130
October 2020	212
November 2020	252
December 2020	137
January 2021	128
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July 2021	87
August 2021	109
September 2021	96
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January 2022	123
February 2022	111
March 2022	158
April 2022	193
May 2022	156
June 2022	74
July 2022	76
August 2022	109
September 2022	90
October 2022	156
November 2022	141
December 2022	73
January 2023	109
February 2023	103
March 2023	136
April 2023	139
May 2023	158
June 2023	121
July 2023	88
August 2023	111
September 2023	95
October 2023	126
November 2023	142
December 2023	87
January 2024	108
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Published: 03 November 2015

What Has Caused Desertification in China?

Qi Feng 1 ,
Xuemei Jiang 3 ,
Xin Wang 3 &
Shixiong Cao 3

Scientific Reports volume 5 , Article number: 15998 ( 2015 ) Cite this article

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Ecosystem ecology
Environmental economics

Desertification is the result of complex interactions among various factors, including climate change and human activities. However, previous research generally focused on either meteorological factors associated with climate change or human factors associated with human activities and lacked quantitative assessments of their interaction combined with long-term monitoring. Thus, the roles of climate change and human factors in desertification remain uncertain. To understand the factors that determine whether mitigation programs can contribute to desertification control and vegetation cover improvements in desertified areas of China and the complex interactions that affect their success, we used a pooled regression model based on panel data to calculate the relative roles of climate change and human activities on the desertified area and on vegetation cover (using the normalized-difference vegetation index, NDVI, which decreases with increasing desertification) from 1983 to 2012. We found similar effect magnitudes for socioeconomic and environmental factors for NDVI but different results for desertification: socioeconomic factors were the dominant factor that affected desertification, accounting for 79.3% of the effects. Climate change accounted for 46.6 and 20.6% of the effects on NDVI and desertification, respectively. Therefore, desertification control programs must account for the integrated effects of both socioeconomic and natural factors.

Desertification of Iran in the early twenty-first century: assessment using climate and vegetation indices

Unintended consequences of combating desertification in China

Drivers and impacts of changes in China’s drylands

Introduction.

Drylands cover about 54 million km 2 , which amounts to 40% of the global land area and are especially common in Asia and Africa, where they account for 58.5% of the world’s dryland area 1 . These regions have suffered from climate change, unfavorable hydrologic conditions, changes in vegetation composition, loss of soil services and desertification; the combination of these effects has generated many adverse consequences, including sandstorms that threaten ecosystem services and human life 2 . In recent years, more and more of the sandstorms that form in desert areas have swept into modern cities in areas such as northwestern China, Africa, the western United States and Australia 3 . In arid, semi-arid and dry sub-humid regions, land degradation that results in a loss of vegetation cover is caused by several factors, including climatic change and human activities and has been defined as desertification . As desertified areas expand, the area of livable habitat will decrease and poverty will be exacerbated 4 . Desertification has become a crucial environmental problem at a global scale and has begun to affect the survival and socioeconomic development of humankind.

Research has suggested that both climate and human activities play important roles in the process of desertification, which is complicated and includes complex interactions between human and natural factors (e.g., climate) 5 . Because of this complexity, past research has generally focused on either simple climate factors or on human activities rather than trying to account for both factors simultaneously. Some studies concluded that climate change affected the soil quality, vegetation cover, species composition and hydrologic cycles in drylands and has therefore led to expansion of the desertified area 6 , 7 , 8 . Others have argued that unsustainable traditional practices such as grazing, logging and exploitation of underground water have created enormous pressures on ecosystems, leading to desertification 9 , 10 . Such human activities can eliminate the vegetation cover that protects the soil against erosion by water and strong winds 9 . However, without an understanding of how the interactions among the abovementioned factors affect desertification, it is difficult to reconcile the different research results. This creates a high risk of misunderstanding the current situation and adopting ineffective policies and programs to combat desertification 11 , 12 .

In northwestern China, desertification is a major ecological problem that has increasingly limited development of the local economy 13 . To control desertification, the Chinese government implemented a series of large-scale mitigation programs, including the Three Norths Shelter Forest Program and the Combating of Desertification Program 14 , 15 . These projects focus on increasing the vegetation cover by prohibiting grazing, planting trees and grasses and constructing shelter forests to protect farmland against blowing sand. The total desertified area has decreased in many areas, but in others, desertification has continued to expand 16 . Several researchers have therefore questioned the effectiveness of solutions such as afforestation in drylands and especially the practice of planting trees in arid areas that lack sufficient precipitation to sustain the trees in the long term, thereby requiring irrigation to ensure tree survival 11 , 17 , 18 .

Because the relative contributions of natural and human factors are unclear, the driving forces for desertification remain unclear. It is therefore urgently necessary to comprehensively study their interacting effects. Determining the relative contributions of natural and human driving forces to desertification would provide insights into the key mechanisms responsible for desertification, thereby leading to more effective responses. This approach is crucial because of the severity of the desertification problems that China faces and the large sums of money being spent to solve these problems. In the present study, we used the normalized-difference vegetation index (NDVI), obtained by means of satellite remote sensing, to monitor the progress of desertification in four regions of northwestern China: the Xinjiang Uyghur Autonomous Region, the Ningxia Hui Autonomous Region, Gansu Province and the Inner Mongolia Autonomous Region. We then combined this data with climate and socioeconomic data to investigate the relative contributions of climate change and human activities to desertification and its reversal. Based on the results of this analysis, we discuss the key driving factors that are contributing to desertification and its reversal and the lessons for planners of China’s ecological restoration strategy. This will provide important information on how to integrate the effects of climate change and human activities to develop solutions capable of mitigating the problems and promoting sustainable development in the regions that are facing desertification.

To represent vegetation cover over large areas using the available long-term data, it is necessary to use satellite remote-sensing data. Of the available indicators, we chose NDVI because it has been used successfully for many years, by many researchers and because it is a good proxy for the actual vegetation cover, especially in arid and semi-arid regions. The NDVI dataset used in this paper came from the AVHRR GIMMS group 19 at a spatial resolution of 8 km. We used the 15-day maximum-value composites (MVCs) for the period from 1983 to 2006. We also obtained monthly NDVI MVC data from 2000 to 2010 from the Earth Observing System (EOS) satellites ( http://glcf.umd.edu/data/ndvi/ ), at a spatial resolution of 500 m. We then converted the 2000 to 2010 NDVI data to use the same temporal and spatial resolution as the 1983 to 2006 NDVI data. To do so, we combined a 16 × 16 grid of EOS pixels to create a single AVHRR pixel and calculated the weighted mean value of the 256 pixels in the grid to represent the overall value for both halves of the month (i.e., the two 15-day products). We used the mean of these two values to represent the monthly mean and then selected the maximum value from monthly data to represent the year. We then performed simple linear regression to determine the relationship between the NDVI values in the AVHRR pixels and in the composite EOS pixels using data for the period of overlap from 2000 to 2006. The result was a moderately strong and statistically significant regression ( R 2 = 0.527, p < 0.05). We then used that regression to convert the EOS data from 2000 to 2010 into the corresponding AVHRR values. The result was a unified NDVI time series from 1983 to 2010.

We obtained the areas of desertification from national monitoring data in 1990, 2000, 2005 and 2010. We also obtained data on nine factors that potentially affected desertification, which we grouped into two categories: socioeconomic factors (the rural population, rural net income, farmland area, number of livestock, area of forest in which agriculture and grazing were prohibited, afforestation area and the length of roads and railways) and climate factors (annual mean temperature and total annual precipitation). The socioeconomic data were obtained from the China Statistical Yearbook from 1983 to 2012 20 . The ecological restoration data were obtained from the China Forestry Yearbook from 1983 to 2012 21 . The meteorological data (annual mean temperature and total annual precipitation) were obtained from the China Climate Yearbook from 1983 to 2012 22 .

To understand how climate change and human activities have affected desertification, we established empirical models of the following form:

We analyzed panel data to identify the key factors and compared their contributions to the area of desertification and to the vegetation cover (as represented by NDVI) during the study period. To avoid the impact of overlapping factors on the results, we employed the regression analysis module of version 11 of the STATA software ( http://www.stata.com/ ) to calculate the regression coefficients for the relationships between all pairs of driving factors. The panel data model is:

where y it is the area of desertification or the vegetation cover for region i in year t , x it is the corresponding socioeconomic factor, u it is an error term and a and b are regression coefficients. To account for the possibility of autocorrelation among the factors analyzed in our regression, we performed the Breusch-Godfrey LM test and found no significant autocorrelation. Based on the results of an F -test, we selected a pooled regression model for calculating the effects of the abovementioned variables on the NDVI and area of desertification in four provinces (Xinjiang, Ningxia, Gansu and Inner Mongolia) located in arid and semi-arid areas of China.

In the pooled model:

We used the standardized regression coefficients to calculate the contribution of the different variables to the changes in NDVI or the area of desertification for the whole study region and for each province independently. The contribution is calculated as follows:

Table 1 summarizes the results of our analysis and the contributions of the driving factors to overall NDVI (for the four provinces combined) in arid and semi-arid regions of China. Based on the results for the pooled model, farmland area, forbidden area (the area in which grazing and agriculture were forbidden), cumulative afforestation area and total annual precipitation were significantly positively related to NDVI change. Their contributions to NDVI change were 16.9, 5.7, 2.9 and 30.0%, respectively, which suggested that precipitation had the strongest effect on vegetation cover change, followed by the area of farmland. Livestock number and the length of roads and railways were significantly negatively related to NDVI change, accounting for 15.9 and 5.8% of the total effect, respectively. Both factors had an effect similarly strong to that of farmland area, but grazing (which is proportional to the number of livestock) had the strongest negative effect on NDVI change. The rural population, rural income and mean annual temperature did not significantly affect NDVI change.

Table 2 summarizes the contribution of the driving factors to desertification change for the four regions. Livestock number, farmland area, road construction and mean annual temperature were significantly positively related to the change in the area of desertification, accounting for 30.8, 21.9, 4.1 and 14.6% of the total effect, respectively, though the contribution of temperature was only marginally significant. As in the analysis of NDVI, livestock increased desertification (probably through vegetation loss caused by grazing). The rural population (10.6%), rural net income (7.8%), area in which grazing and agriculture were forbidden (4.2%) and total annual precipitation (6.0%) were significantly negatively related to the change in the area of desertification, though the contribution of annual precipitation was only marginally significant. However, the afforestation area was not significantly correlated with desertification dynamics, which suggests that afforestation did not contribute to desertification control in the long term.

The contribution of each variable to the change in the area of desertification in the four provinces ( Fig. 1 ) differed among the provinces, suggesting that the drivers are specific to the context of each province. The rural population and livestock numbers in all four provinces were positively related to increases in the area of desertification, but the other variables showed different effects in different regions. In Inner Mongolia and Xinjiang, afforestation was the most important contributor to desertification, accounting for 41.2 and 24.2% of the total effect, respectively, whereas afforestation resulted in restoration in Gansu and Ningxia, accounting for 56.1 and 14.1% of the total effect, respectively. Remarkably, forbidding agriculture and grazing was associated with decreased or only slightly increased desertification in all four regions, which means that this approach is potentially effective for ecological restoration. The effects of road construction also differed among these provinces. For Inner Mongolia and Xinjiang, road construction decreased desertification, possibly because vegetation restoration and irrigation projects tend to be associated with additional road construction in arid regions such as Inner Mongolia and Xinjiang.

Our results demonstrate that the combination of significant rural socioeconomic factors and significant climatic factors had an important effect on vegetation cover (as measured by NDVI) and on the area of desertification in the four arid and semiarid areas of China that we studied. In these regions of China, the high level of human activities and the strength of the associated impacts result from cultivation, grazing, destruction or harvesting of herbaceous vegetation and logging forests to produce firewood and rural construction materials. The local crops are mainly wheat, potato and cotton and their areas can be detected using NDVI data during their growing seasons; this may partly explain why the area of farmland had a positive effect on NDVI ( Table 1 ). The expansion of crops can potentially increase the vegetation cover, but this increase is temporary; for most crops, the soil remains uncovered during the fallow season. If the farmland is abandoned without the implementation of effective protection of the soil, desertification will accelerate due to increased erosion by the wind 22 . As the rural population decreased during the study period 19 , the pressure from the demand for land should also have decreased. Although the rural population is often considered to be a major driving force for environmental damage, it is also an important force for managing farmland and grazing to avoid damage to vegetation.

Rural poverty alleviation is as important as desertification control and ecological restoration 23 , 24 . Even though the rural net income gradually increased every year during the study period 19 , it has been difficult to raise farmers and herders out of poverty. The first problem is that the harsh environment and the large population of impoverished rural residents make the income from traditional farming highly vulnerable to natural disasters such as drought and to fluctuations of market prices 25 , 26 . Second, the study region’s simple economic structure makes it difficult to provide alternative forms of employment that would improve rural incomes. Third, the burden on residents of national efforts to control desertification is too heavy. The subsidies provided by the government to compensate residents for grazing and farming prohibition are less than the increasing cost of production and household expenses that result from these government policies 22 , 27 .

For rural residents in the arid and semiarid areas of China, their income mainly comes from the land and the harshness of the environment (particularly the lack of water) means that earning this income jeopardizes the ecological environment; in particular, it can lead to soil erosion and an expansion of desertification. As our analysis revealed, the contribution of livestock is considerable. This is likely to be because poor communities must increase their livestock numbers to provide income or a food source; as this occurs at the expense of the environment, it exacerbates desertification. Our study confirmed that grazing and farmland expansion were important drivers of land degradation for all four provinces. Although the policy that restricts grazing has been implemented for almost a decade, livestock remain a significant cause of desertification. Analyses such as the present study reveal important impacts of such socioeconomic factors on desertification and government ecological restoration policy that is implemented to counteract desertification must account fully for the economic losses of local residents under new policies by providing adequate subsidies or alternative means of employment. Without such efforts to protect the livelihood of these people, they have no ability to protect their environment, even when they understand that their activities are causing significant damage to that environment 24 .

The arid and semiarid areas of China, which occupy half of China’s total land area, are likely to face increasing stress from climate change, which will exacerbate existing water shortages and place additional stress on vegetation communities that are already being stressed by regional warming 28 . In our study, rural socioeconomic factors had a slightly stronger effect than climate factors on NDVI, accounting for 53.4% of the total effect. However, the statistically significant climatic factor (total annual precipitation) had a cumulative effect (30%) similar to that of the statistically significant socioeconomic factors (27.2%) on vegetation restoration. The cumulative values for these two groups of factors were sufficiently close that climate change and human activities appear to have accounted for similar proportions of the overall changes in vegetation cover.

For the factors that controlled desertification, the contribution of socioeconomic factors was clearly dominant (79.4% of the total effect for all factors, versus 79.3% for only the significant factors; Table 2 ); natural factors (temperature and precipitation) accounted for a much smaller portion of the total effect. Thus, human activities have had the dominant effect on desertification, but climatic factors have been significant and their effect will become increasingly significant as a result of the warmer and drier climate produced by global warming. Based on the warming trend in northwestern China 28 , agriculture, grazing and afforestation, which are sensitive to climate, must be carefully assessed to predict the effects of changes in temperature and precipitation on their impacts.

Some researchers have questioned the effects of planting trees in restoration projects to control desertification because this approach has not performed as well as expected 11 , 27 . In the present study, our results show that the contribution of the area of forest in which agriculture and grazing were prohibited (the “forbidden” area) and of the afforestation area averaged only 4.3% of the total effect for NDVI and only 2.1% for the area of desertification. The complexity of ecosystems and the even more complex interactions between humans and nature 29 , 30 mean that the simplistic solution of planting trees in arid regions is unlikely to be a broadly applicable way to restore degraded dryland ecosystems. For example, planting trees (which often have low water-use efficiency) in arid regions often requires supplemental irrigation, which exacerbates the stress on an already limited water resource 12 , increases evapotranspiration and can even exacerbate soil erosion if the trees outcompete herbaceous vegetation for water, leading to decreased vegetation cover at the soil surface 5 , 18 . The lack of a significant impact of the cumulative afforestation area on desertification means that the positive effects of afforestation in the short term may be compromised by the negative effects of afforestation on water availability in the long term. The low survival rate of the trees 11 can also represent a large waste of labor and money. In many arid regions, restoration using herbaceous vegetation will produce better results than using trees or shrubs 31 . Although China’s huge national ecological restoration policies, such as the Three Norths Shelterbelt Project, have improved the vegetation cover in many areas, the potential risks should receive more attention from policy makers and restoration managers. The large variation among regions shown in Fig. 1 provides additional support for this recommendation, since these results demonstrate the strong effect of differences in local conditions.

The effects of ecological restoration in desertified areas result from the interactions among multiple factors. In the arid and semiarid areas of China, our results show roughly comparable impacts of socioeconomic factors and climate change for NDVI but stronger socioeconomic effects on the area of desertification. However, the strengths of the impacts varied widely among the four parts of our study area. This means that it will be difficult to fully understand the driving forces responsible for desertification in China without understanding the unique context of each region and that monolithic policies will work less well than adopting policies that address the most significant driving factors for each region. It is evident that the relationships between the driving factors and the changes in NDVI and the area of desertification are complicated. The most important driving factors varied among the regions ( Fig. 1 ). Thus, despite the significant impacts of several driving factors for the overall study area ( Tables 1 and 2 ), policy development must be based on a careful examination of each individual region using a method similar to the one developed in the present study to identify the most significant driving factors for that region. Only then will it become possible to develop solutions that attack the most relevant problems. This finding has significant implications for achieving ecologically sustainable development in the degraded lands of China.

One limitation of our study is that we did not account for the sociological factors that underlie the human factors that we included in our analysis. This suggests that interdisciplinary research will be required to fully understand the sociological factors and their interaction with natural factors so that appropriate policy measures can be developed to focus on those factors and interactions. Although we made an effort to control for the uncertainty in our analysis by including the error term u it in the regression analysis, an additional area for future research will be to more precisely determine the error and uncertainty that are associated with the socioeconomic factors. This will allow future researchers to better control this error term and more precisely estimate the impacts of individual factors. In addition, the regression relationship we developed will need to be validated by means of a pilot study that provides more detailed information. The results of our NDVI analyses are not surprising, since similar conclusions have been published by many researchers. For example, overgrazing and road construction are likely to result in decreased vegetation cover, as Li and Li 32 found in their study of a government policy to end the traditional nomadic culture; the resulting sedentarization contributed to overgrazing, which in turn led to grassland degradation. Deng et al. 33 found that road construction may lead to ecosystem degradation in high-quality grassland.

Although our method of identifying the contributions of each driving factor is defensible for providing a broad overview, it is likely that there is a better method for this kind of analysis that will support more precise analyses for individual regions. This method should be identified in future research to improve the ability of this research to support restoration planning.

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Acknowledgements

This work was supported by the Key Project of the Chinese Academy of Sciences (KZZD-EW-04-05). We thank Geoffrey Hart of Montréal, Canada, for his help in writing this paper. The opinions expressed here are those of the authors and do not necessarily reflect the position of the government of China or of any other organization.

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S.C. designed the research; H.M. and X.J. analyzed the data; Q.F., H.M., X.W. and S.C. wrote the main manuscript text; and X.J. prepared Figure 1 and Tables 1–2 . All authors reviewed the manuscript.

Contributions (%) of the driving factors to changes in the area of desertification based on the results of the regression analysis.

The data have been broken down for the four study areas and are based on the relationships among the values of the driving forces. “Forbidden” represents the area of forest in which agriculture and grazing were prohibited and “Road” represents the length of roads and railways. We created this figure in using ArcGIS 10.0 for maps.

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Causes and Impacts of Land Degradation and Desertification: Case Study of the Sudan

Faculty of Law
Department of Forest Sciences
Viikki Tropical Resources Institute (VITRI)
Forest Ecology and Management

Research output : Contribution to journal › Article › Scientific › peer-review

Original language	English
Journal
Volume	3
Issue number	2
Pages (from-to)	40-51
Number of pages	12
ISSN	2165-882X
DOIs
Publication status	Published - 2013
MoE publication type	A1 Journal article-refereed

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5203 Global Development Studies
4112 Forestry

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10.5923/j.ijaf.20130302.03
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T1 - Causes and Impacts of Land Degradation and Desertification

T2 - Case Study of the Sudan

AU - Abdi, Omar A.

AU - Glover, Edinam K.

AU - Luukkanen, Olavi

N2 - Desertification, a phenomenon referring to land degradation in arid, semi-arid and dry sub-humid regions as a result of climatic variations and human activities, is considered as one of the most severe environmental and socio-economic problems of recent times. The principal aim of this study was to explore the impacts of desertification, degradation and drought on both the natural resources and man's livelihood in the Sudan and to suggest appropriate forest resource management interventions. The study was based on a fact finding tour in the Sudan and data collection on drought trends as reflected in rainfall trends in the study area, and on trends concerning the productivity of natural resources. Information was also compiled from existing records on rainfall, forest land cover, forest stocking, rangelands and carrying capacity and on agricultural productivity and population trends. Results showed that in rain-fed agricultural zones in the Sudan, deep ploughing and leveling of the surface soil caused an increase in its susceptibility to wind erosion, which, in turn, has led to a severe decline in its fertility and, in some places, the formation of sand dunes. The implications of these trends on the natural resource base include environmental degradation, food insecurity and aggravation of income inequalities among the Sudanese producers. The study has suggested Agroforestry technology as a potential solution to this continued problem of declining rural agricultural production in the Sudan.

AB - Desertification, a phenomenon referring to land degradation in arid, semi-arid and dry sub-humid regions as a result of climatic variations and human activities, is considered as one of the most severe environmental and socio-economic problems of recent times. The principal aim of this study was to explore the impacts of desertification, degradation and drought on both the natural resources and man's livelihood in the Sudan and to suggest appropriate forest resource management interventions. The study was based on a fact finding tour in the Sudan and data collection on drought trends as reflected in rainfall trends in the study area, and on trends concerning the productivity of natural resources. Information was also compiled from existing records on rainfall, forest land cover, forest stocking, rangelands and carrying capacity and on agricultural productivity and population trends. Results showed that in rain-fed agricultural zones in the Sudan, deep ploughing and leveling of the surface soil caused an increase in its susceptibility to wind erosion, which, in turn, has led to a severe decline in its fertility and, in some places, the formation of sand dunes. The implications of these trends on the natural resource base include environmental degradation, food insecurity and aggravation of income inequalities among the Sudanese producers. The study has suggested Agroforestry technology as a potential solution to this continued problem of declining rural agricultural production in the Sudan.

KW - 5203 Global Development Studies

KW - 4112 Forestry

U2 - 10.5923/j.ijaf.20130302.03

DO - 10.5923/j.ijaf.20130302.03

M3 - Article

SN - 2165-882X

JO - International Journal of Agriculture and Forestry

JF - International Journal of Agriculture and Forestry

DOI: 10.5923/J.IJAF.20130302.03
Corpus ID: 13794490

Causes and Impacts of Land Degradation and Desertification: Case Study of the Sudan

O. A. Abdi , Edinam K. Glover , O. Luukkanen
Published 2013
Environmental Science, Geography
International Journal of Agriculture and Forestry

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Desertification in agricultural lands: approaches to mitigation, theoretical approaches and practical assessment of socio-economic effects of desertification in mongolia, natural and human-induced land degradation and its impact using geospatial approach in the kallar watershed of tamil nadu, india, the preliminary study of anthropogenic and natural drivers of desertification in drylands of south punjab, pakistan, land preservation uptakes in the escarpments of north-eastern ethiopia: drivers, sustainability, and constraints, the impact of land degradation on agricultural productivity in nyabihu district-rwanda, a case study of rugera sector, devastating effect of forest degradation in southern guinea savanna of nigeria, temporal analysis of drought characteristics in the tropical semi-arid zone of nigeria, impact of desertification on livelihoods in katsina state, nigeria, environmental responsiveness towards desertification and land degradation: a review of literature on restoration strategies in dryland communities in africa, 68 references, agroforestry and sustainable land-use in semi-arid africa, the causes and consequences of environmental changes in gedaref, sudan, approaches to halt and reverse land degradation in kenya: agroforestry development and environmental sustainability, wildlife water utilization and importance of artificial waterholes during dry season at ruaha national park, tanzania, on the question of the ''recovery'' of the rains in the west african sahel, impact of carbon storage through restoration of drylands on the global carbon cycle, rainfall variability in west africa during the years 1950-90, soil management for crop production in the west african sahel. ii. emergence, establishment, and yield of pearl millet, the sahelian drought may have ended during the 1990s, cultural barriers to climate change adaptation: a case study from northern burkina faso, related papers.

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Causes and Effects of Desertification on People and the Environment

The word ‘desertification’ may seem like a word depicting a very distant and abstract environmental problem that most of us do not consider being important in our daily lives. But we couldn’t be more mistaken, for desertification is slowly creeping up into our lives and has the power to change everything.

Higher food prices, water availability, violent conflicts for land, migration, increasing poverty, pollution from wind-blown dust particles coming from distant lands, could be the outcomes of desertification if we let it consume more of our planet.

The loss of fertile land to desertification has brought an end to many majestic civilizations throughout the human history. For example, the destruction of the native tropical forest in the Indus Valley opened up a pathway for the desert to claim more and more land, leading to the doom of the Harrapan Civilization. Sadly, the very same process continues to threaten the existence of at least 1.5 billion people (mainly from developing countries) until the present day [1] .

One third of the land surface on Earth has fallen victim to desertification and according to the estimates, another 12 million hectares (approx. 30 million acres) more turn into barren deserts every year [1,2] . For comparison, it is the same size like the area of New York State turning in desert just within a year [3] .

Do we have so much free land available that we do not need to be concerned about this?

Let’s have a look where it all started and what are the consequences.

What is the process of desertification?

Desertification is a process by which fertile land is transformed into desert as it becomes progressively drier and unable to support any plant growth for food production. Unlike the natural desert ecosystem with well-adapted species still inhabiting the area, desertified lands are often devoid of natural life without a healthy ecosystem in place that would perform life-supporting services, like new soil formation and nutrient cycling. This is what makes the reversal of the process extremely difficult.

The official definition by the United Nations Convention to Combat Desertification (UNCCD) that has been widely used since it’s formulation in 1994 is: “desertification is land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic fluctuations and human activities.” UNCCD also highlights that it is important to note that desertification is not a natural process of deserts expanding to new regions, it is a form of land degradation caused primarily by human activity in vulnerable areas.

The loss of land to desertification has major impact on many places on our planet today and is expected to affect humanity even more in the future as population numbers will grow bigger and the availability of natural resources will decline.

Where is desertification happening the most?

Pretty much every continent has some dryland area that is currently threatened by desertification if no immediate preventative measures will be taken. You may be even able to identify the most vulnerable areas yourself, as they include grasslands, steppes, prairies, savannahs, shrublands and woodlands.

Countries affected by desertification do not have to be located only in hot regions of the world because it is the local climate and land use that shape the health of the land. For example, up to 50 percent of the Canadian Prairies spreading over Alberta, Saskatchewan and Manitoba are likely to battle with some of the negative effects of desertification in the upcoming years.

And globally, the risk of losing more land is getting higher with increasing summer temperatures and less frequent and erratic rain patterns we are experiencing in the last years.

However, the main reason why desertification goes widely unnoticed is that 90 percent of people affected by this phenomenon currently live in developing countries, mainly in Africa and Asia, and belong to the world’s poorest [4] .

But how does such a serious form of land degradation happen and how come we let it advance so far?

What causes desertification?

Lands turn to desert due to a number of reasons, but much of the desertification that is occurring around the world today is caused by human activity on lands that are extremely vulnerable to overexploitation and improper agricultural methods.

The following are some of the primary causes of desertification in our world.

#1 Overgrazing

Overgrazing and desertification have been always closely linked together.

In dry regions, grass and other small vegetation is necessary to keep the soil in place to prevent erosion and further damage to the soil. However, it is the paradox of life that especially in these vulnerable regions, animal herding is often the only livelihood people can have and there are no restrictions in place that would regulate the maximum number of animals for a given space.

When people gather and keep too many animals in one area, grasses start dying because their roots are often weakened by animals constantly stepping on them and plucking out newly re-growing parts before plants have time to grow resistant enough and to multiply.

After some time, no vegetation remains to prevent soil from blowing or washing away. So, people move the livestock to another piece of land where the process repeats. If this occurs long enough, it leads to extensive desertification.

There have been numerous cases when overgrazed areas of land became severely damaged.

Scientists have, for example, confirmed that overgrazing is the primary reason why around 70 percent of the once pasture rich Mongolian steppe is slowly overtaken by the Gobi Desert now.

The situation in Mongolia is alarming, particularly because this land degradation has taken place just recently. Since 1990s, when the lack of jobs due to the breakup of the Soviet Union forced people to rear livestock as their only possibility to earn money [6] .

Similar scenario has happened even with the Bedouins grazing their herds freely over the fragile steppe in Syria. For 50 years, large herds of livestock grazed over the Syrian steppe until the effects couldn’t be overlooked anymore. Overgrazing has become a problem that has escalated into an ecological and agricultural collapse in the country.

#2 Unsustainable agriculture techniques

The world’s drylands cover approximately 40 percent of the total land mass. They are home to more than 2 billion people, so it is clear that many of these areas are farmed, even though they are very fragile and can easily turn barren.

Through inconsiderate farming methods like heavy tilling, planting of unsuitable crops and leaving soils exposed to wind and rain erosion, farmers only speed up the process of desertification in exchange for poor quality crops with low economic value. Besides, while preparing the soil for sowing, natural vegetation that holds the brittle soil in place is removed, letting the last bits of the productive soil layer fully wear away in just a few short seasons.

Another common problem of the crop cultivation in vulnerable areas is the employment of improper irrigation methods, such as canal irrigation. These irrigation methods often lead to a buildup of salt in soils. Increased salinity happens because irrigation water mobilizes naturally occurring salt in these soils. Additionally, artificially added water also rises otherwise low groundwater level which in turn dissolves even more salts [7] .

Salt buildup on cultivated lands, then, makes it difficult for crops and other plants to grow, further exacerbating degradation of these lands.

A sad example of the destructive power of such a mismanagement is the drying out of the Aral Sea. The Aral Sea used to be the world’s fourth largest saline lake until 1960s, when the Soviet government diverted the Amu Darya and Syr Darya rivers, which have been feeding the lake with fresh water.

Why would they do that?

Because of ambitious cotton farming projects in the dry Aral Sea basin that needed irrigation.

Cotton farming in the desert combined with poorly build irrigation channels, from where lot of water simply evaporated, decreased the size of the Aral Sea by 90 (!) percent [8] . And the land of the dry lake basin became a saline desert where nothing grows on its own.

Local communities that used to live by the lake rich with fish and biodiversity, live now only amidst dust, pesticide pollution and scorching heat. They are the ones who have seen the ugly face of desertification slowly reaching their doorstep, and they are the ones who are also witnessing how fast sand and dust consume even more land every year.

#3 Deforestation

In November 2016, Guardian published an article with the title “We have been almost buried: the Sudanese villages being swallowed by sand.” The article goes on describing the struggles of villages in Sudan’s River Nile State that have succumbed to desertification after years of extensive deforestation and worsening droughts. Villages that were once surrounded by forests so dense that you could get lost in them, are now disappearing under the sand.

Deforestation is one of the leading human causes of desertification. Forests are being cut down at much larger scale than ever before, to be used as fuel, to provide products we use in our daily life, or to simply create more space for agriculture to sustain growing human population.

When the trees and other vegetation in an area are gone, there are no roots that would hold soils in place, there is no canopy that would shield the ground from the direct rainfall or from the sun’s heat. The bare soil then easier dries out and turns to dust, which can be blown and washed away in a single storm.

Once the soil is degraded and the precious nutrients are lost, only infertile and lifeless swaths of land are left behind. And what’s more, without trees, even the local climate becomes drier due to the lack of water evapotranspiration from tree canopy, which reduces cloud formation in the region and results in less rain.

After all, history tends to repeat itself, so perhaps the story of the Maya could serve as a warning sign for us. According to model simulations ran by the NASA Goddard Institute for Space Studies , the end of the Mayan empire probably happened due to prolonged droughts caused by cutting down the rainforest to expand their cities and plant crops to feed their growing population [9] .

#4 Unsustainable water management

Drylands, the most susceptible areas to desertification, are characterized by a scarcity of water during certain periods of the year. This means that the original ecosystem of these lands is well-adapted to withstand dry seasons during which plants enter so called summer dormancy, a temporary cessation of growth, in order to preserve themselves, only to turn green and strong as soon as rains come again.

You can see this wonderful resilience of the plants in Serengeti. During the rainy season, the vast grass plains turn lush green, providing a rich grazing opportunity to hundreds of thousands of the Africa’s most iconic herbivores, only to fade when the dry season comes.

But the problem appears when we try to change these natural cycles and expect a steady crop production or sufficient pasture for livestock from these lands all year long. Under circumstances like these, people often overextract water from available resources like creeks, rivers or even groundwater to irrigate the crops.

Lack of water to support farming and desert sands encroaching villages are already causing trouble to rice farmers throughout the regions of northern China. While farmers despair about their inability to cultivate rice fields, local agronomists confirm that it was the water overextraction to create rice paddies that has significantly contributed to the current desert expansion [10] .

The problem of worsening desertification doesn’t have to be linked only to agricultural lands, unsustainable water management happens even in cities and tourist destinations that are build in arid or semi-arid areas. These places often draw high amounts of groundwater from natural aquifers, not letting them naturally replenish and eventually facing water scarcity just like Cape Town in South Africa.

All problems related to desertification can eventually be traced back to water related problems. — DESIRE Scientific Report no. 4

#5 Overpopulation and overexploitation of natural resources

Our planet’s ecosystems sustain life only when balanced. They can cope with incremental challenges and adapt, but beyond a certain tipping point they collapse. Unfortunately, desertification is a proof that in some places, we have reached this tipping point.

A rapid increase in human population, especially in vulnerable areas of Africa and Asia, has exceeded the recovery capacity of dryland ecosystems. As “harsh” as this may sound, the reason is very simple.

More people means higher demand for natural resources (including water(!) and space to grow food and build settlements. But trying to provide for more people easily results in overexploitation of available resources, even if unwillingly. Just look at previously mentioned examples, they all point to this conclusion.

Once the overexploitation takes place, desertification often follows, leaving behind only barren land and misery for those who haven’t left.

One region of the world that has seen many of these negative effects combined is Sub-Saharan Africa. The region currently faces extensive desertification caused by numerous factors. These factors include very high birth rates and thus expansion of agriculture into unsuitable areas, uncontrolled tree cutting for a fuel, all connected with effects of climate change and bad government policies.

#6 Urbanization and development of tourism

Not many people realize this when walking on the streets of their city or some magnificent tourist resort, but in order to build these structures, original ecosystems had to be irreversibly wiped out. And together with ecosystems disappear even natural resources that were once present.

This means that natural resources, which are continuously needed for the proper functioning of any densely inhabited area, have to be taken from the surrounding environment. However, as the trend of urbanization increases, the demand for resources only grows bigger, drawing more and more resources and leaving behind degraded lands that easily succumb to desertification.

Furthermore, additional problem arises from the space problems. As cities expand, more land in the vicinity is used for the development projects. Even though this often represents fertile land that would have been suitable for agriculture more. We should not forget that most of the human settlements were built along fertile soils, rivers, or other resourceful places that offered some great advantage to their inhabitants. Their loss to buildings and other infrastructure is, therefore, rather wasteful.

Land degradation due to urbanization has affected strongly many countries such as Egypt, Iraq, Turkey, Spain and other places with hot climate, where urban and tourist areas spread along the rivers or coastlines, sealing these lands and pushing farming away onto marginal lands, which will only accelerate their desertification over the time [11] .

#7 Famine, poverty and political instability

While desertification certainly leads to these problems, they can also be its cause . This is because people on the brink of famine, extreme poverty or political instability in their country need to solve the crisis at the moment and do not think about sustainable cultivation strategies.

Unfortunately, outcomes of their compromised livelihoods are often poor land use practices, such as grazing animals on eroding lands, illegal cutting of forests and unsustainable crop cultivation, which only contribute to the soil destruction beyond repair and put lives of people even more in danger.

Greentumble’s writer Deogracias has described how is the problem of deforestation linked to the livelihood of some people in his country, Malawi. You can read the whole story here to get a better understanding about the situation in this developing country and reasons why preventing desertification gets difficult in some areas.

#8 Climate change

So much could be written about the effects of climate change on the health of our lands, as climate change can lead to land degradation for many reasons, and it is very often climate change that exacerbates the progress of desertification in increasingly many places.

But it is important to realize one thing if we want to know how does climate change cause desertification. As we continue to remove natural vegetation from landscapes, we change radically the water absorption capacity of soils. With less permanent vegetation that would help retain moisture in soils and with less moisture evaporating into the air from plants, less clouds form in that particular area. That means also less rain throughout the year.

With significantly reduced rainfall, drought occurs and triggers problems such as failing harvests, drying creeks and boreholes, poor pasture that weakens livestock, and more frequent outbreaks of wildfires that destroy remaining vegetation.

It is these problems that pressure people to slip into the vicious cycle of repeating all the previously listed causes of desertification–actions which naturally open up the door to the ecological catastrophe of irreversible land degradation.

One of the very recent examples of climate-induced desertification is the disappearance of the lake Poopó, lying in a high altitude of semi-arid plains in Bolivian Andes. Formerly, the second largest lake in Bolivia filled with diversity of fish and birds had completely dried up just in the span of three years, 2014 to 2017. All that is left of the lake is just a large salt desert. The reasons why this has happened are longer periods of droughts and the overextraction of water for irrigation and mining projects [12] .

What are the effects of desertification?

In the introduction of a document called ‘Desertification: The invisible frontline’ from UNCCD is stated: “Desertification is a silent, invisible crisis that is destabilizing communities on a global scale.”

The document further goes on examining the serious and complex web of problems that have arisen from worsening land degradation of the earth’s drylands, which are home to 2,000 million people, comprise of 44 percent of all the world’s cultivated land and should sustain 50 percent of the world’s livestock [13] .

These are huge numbers and huge level of dependency upon these lands that should not fail us. Do you know what that means? It means that the effects of desertification can be extremely serious and not only for us, but for the balance of the whole planet.

Here is what we can expect…

#1 Vegetation is damaged or destroyed

Desertification reduces the ability of land to support plant life. Loose soil buries plants or exposes their roots to the sun, so they cannot fulfill their function. With plants dying, already scarce rainwater gets washed away instead of being drawn into the soil, which only scales up the problem as remaining plants do not have enough moisture to survive dry spells as they used to.

Additionally, if the land is used for grazing at this stage, it only results in a quicker loss of plant species and total degradation.

#2 Soil becomes infertile

Topsoil is crucial for plant growth because it contains most of the organic matter and 50 percent of important nutrients such as phosphorus and potassium. It is in topsoil where large pores and soil aggregates form, allowing for proper water infiltration and aeration.

As desertification occurs, this most productive layer of the soil gets blown or washed away from the surface rather quickly because there is no vegetation that would protect it, and nutrients with organic material are lost for good. As the soil dries out, it hardens, and it becomes difficult for any rainfall that does occur to penetrate below the soil’s surface.

Due to unfavorable conditions, plants grown on these damaged soils strive and often do not produce sufficient yields. What remains left is only a lifeless pile of dust instead of a life-giving medium.

Furthermore, through the use of unsustainable irrigation techniques, salt concentration can also rise in many cultivated soils, rendering the soil useless for growing crops or other plants.

Iran is a country that has been suffering of this problem. Most of the agricultural land in the country has increased salinity due to large-scale irrigation plans and progressively drier climate.

Faulty irrigation projects have resulted not only in the soil infertility, they have also decreased water table of the country’s largest lakes by 80 percent and more, exposing shores to the effects of rapid drying out and land degradation [14] .

#3 Soil erosion gets worse

As you may have noticed, desertification problems are often related and lead to one another. The link between soil erosion and other consequences of desertification only confirms this, as erosion is another negative outcome but also a catalyst of previously mentioned problems.

In many cases, increased water runoff from desertified areas wreaks havoc on neighboring lands, eroding soils, damaging vegetation and making soils extremely vulnerable to encroaching desert.

When this happens, weakening soils get also directly exposed to wind, which often picks up last pieces of drying topsoil and mixes them with dust from already degraded parts, exacerbating the problem and creating far-reaching dust storms.

This is exactly what has been happening in the Sahel.

According to the newest data, the Sahara Desert has been gradually spreading over the grasslands in the neighboring Sahel area. Compared with the data from 1920s, Sahara has already expanded by 10 percent.

In recent years, the desert has advanced southward to lake Chad, which used to be an important source of water and livelihood for 30 million people from eight African countries, but dramatic declines in water level due to droughts and loss of land to desertification have brought only insecurity and suffering upon these communities [16] .

Besides other contributing factors, Sahel farmers are partially to blame because they have removed trees to cultivate crops in this semi-arid area, and thus speeding up Sahel desertification by exposing soils to erosion [15] .

Soil erosion is often one of the final steps that closes the loop of continual soil deterioration that is difficult to revert.

#4 Increased vulnerability to natural disasters

Desertification makes natural disasters worse because it reduces natural resilience of ecosystems. This means that affected areas and even adjacent areas have compromised capacity of withstanding extreme weather events. Desertification also increases vulnerability of whole regions to the unpredictable effects of climate change .

Events such as flash floods, landslides and dust storms, become stronger in areas with heavily degraded soils. Without plants stabilizing the soil and slowing down the runoff, rainwater flows faster and floods human settlements in the blink of an eye.

Except causing damage, flood water also picks up many unwanted pollutants while making its progress through urban areas, landfills, wastelands, or agricultural lands where fertilizers and pesticides were used. These pollutants then remain deposited in the soil or wash off into rivers, creeks or lakes.

Flooding is not the only problem, sand storms are another big issue, mainly because wind-blown particles (including those that are polluted) can travel long distances and cause health problems to people even in distant urban areas.

Inhabitants of the Aral Sea region are well-familiar with this problem. Watch the video to learn more about destructive sandstorms and advancing desertification they have to face more frequently.

#5 Polluted sources of drinking water

Vegetation plays an important role in cleaning our water. Plants and trees function like natural water filters, storing pollutants, such as heavy metals, pesticide residues, fertilizers and other, in their own bodies. As mentioned previously, grasses and other perennial plants also prevent water runoff by slowing it down and promoting rainwater infiltration into soils.

Barren soils lack this green filter, and therefore, many harmful substances enter groundwater reservoirs or easily wash off into lakes and rivers.

Besides constantly eroding soils by creating gullies and channels each time it rains, water also picks up loosen soil particles and transports them into water bodies. This leads to increased sedimentation and eutrophication –both processes disturb aquatic ecosystems and deteriorate water quality.

What’s worse is that these effects can be felt even thousands of miles away from where the problem originated. There have been many records of water scarcity and pollution problems that are linked to desertification or other forms of land degradation across dry African and Asian countries.

For example, China’s autonomous region of Ningxia owes its existence to the Yellow River, which has been the only life giver to communities of rice farmers in this arid land that is encircled by sand dunes. Unfortunately, due to the unsustainable water management of diverting water to rice paddies, soil salinity has increased, forcing farmers to use high amounts of fertilizer to save their harvest. And it is these fertilizers that are poisoning scarce sources of potable water, as they are flushed with every rain into the river and drinking wells of people [10] .

#6 Rise of famine, poverty and social conflicts

Desertification is a serious form of land degradation that results in the destruction of natural ecosystems and the end of services they provide for us . This includes natural filtration of water for drinking, climate regulation, recycling of nutrients, carbon sequestration, soil regeneration. There is probably no need to explain how crucial these services are for our wellbeing.

When ecosystems cease to support us and our livestock, only bad things happen. Bad things like prolonged episodes of famine, diseases from water scarcity, fights for thinning resources and death of people, children, animals.

Many African countries, especially in the Sahel area, are experiencing insecurity that only gets worse and worse every year. Climate change, bad management of scarce resources, weak political structure only lead to hunger, which in turn gives rise to conflicts.

One of the latest humanitarian crises has been declared in countries that have been dependent upon resources provided by lake Chad, where lake water gets quickly replaced by inhospitable sand dunes, destroying fishing and farming communities.

Not only that up to 6 million people suffer of hunger in the Chad Basin recently, they are also terrorized by Boko Haram, one of the most dangerous terrorist groups in the world. Boko Haram is believed to constitute of young people deprived of livelihood possibilities due to constant disputes over disappearing water among diverse ethnic groups, inhabiting the area [17] .

Desertification has destroyed even lives of nomadic Bedouins and farmers in Syria. Due to unrestricted grazing of the steppe by livestock combined with the influence of climate change, Syrian land has become so damaged that it has turn into lifeless dust. According to expert opinions from FAO and UN, this high level of land loss to desertification is what has triggered a civil war in the country. The war that has been going for nearly a decade now [18,19,20]

#7 Forcing mass migrations

People have been always on the lookout for fertile lands where they can build their settlements and prosper over long time periods. It is no wonder, that throughout history, desertification events have been a major driver behind migrations of large human populations.

One of the biggest transitions that has forced first farmers in the early Holocene to abandon their lands happened when their previously fertile lands started to turn drier and drier. Unable to grow crops, farmers had to leave their villages in search of better lands. And it was good they did, because since then, the area they have been cultivating became one of the biggest deserts on Earth – the Sahara Desert.

While the main reason for desertification of the Sahara lies in slight changes of the Earth’s orbit, which affected the intensity of the monsoonal rains in the area, early farmers might have been to blame as well.

According to a new hypothesis, scientists believe that herds of domestic goats and vegetation burning to cultivate grasslands of the previously green Sahara could have sped up the process of drying up . Be it true or not, unfavorable conditions still forced early people to leave their homes and everything they were familiar with.

The same happens even at this very moment and will be happening in the future. UNCCD estimates that advancing desertification could displace globally 50 million people in the next 10 years [21] . And when you think about it, it’s just a natural reaction of any living organism to survive – “fight or flight.”

Since small subsistence farmers do not have the means to ward off sand dunes crashing their houses and burying their crops, all they have left is to gather their possessions and leave.

In many instances, these people go to larger cities, hoping for better life by finding a new livelihood. Unfortunately, that’s not always the case, as they often lack the skills that are needed for urban jobs. Some of these families then end up living in poverty in slums.

#8 Caused historical collapses of civilizations

There are many historical accounts of how various people groups throughout human history experienced collapse of their civilization as drought and desertification occurred to their lands. The reason is simple, people lost their ability to grow food, water resources became scarce and their animals got weak from not having enough to eat.

These negative events are directly linked to the wellbeing of people. As soon as livelihoods are endangered, people turn against each other, which sets in motion series of events that lead to the collapse.

Examples of civilizations that met their doom due to droughts include the Carthage Civilization, the Harappan Civilization, people groups in Ancient Greece, the Roman Empire, and people groups in Ancient China [22] .

#9 Extinction of species

Extended droughts, prolonged flooding or sudden extreme changes in temperature can deplete food sources of species causing starvation. Species that once lived in a fertile and productive climate may not survive in a newly desertified region.

With a changing ecosystem, species must adapt to their new climate or migrate to a more favorable climate. If they fail to do so, they will become extinct for their inability to cope with a sudden change of their environment.

This is another very alarming aspect of the desertification problem, because we need biodiverse ecosystems to survive. We need abundance of plants and animal species richness to have oxygen to breathe, clean water to drink and nutritious food to eat. If biodiverse ecosystems disappear, we will be left with pollution, drought, hunger and lack of resources.

That doesn’t sounds like such a bright future, does it?

This list of causes and impacts of desertification is just a brief fraction of the whole scope of such an extensive problem taking place on our lands every day.

Majority of those who are affected the most by this problem are as usual the world’s poorest nations where people struggle daily with the direct impacts of climate turning against them, and deserts claiming more of their already scarce soils.

Therefore, it is important to realize after reading this article how valuable soil conservation is . And try to do everything in our power to help protect natural resources we have.

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Hot deserts - AQA Desertification - causes and prevention strategies

Hot deserts are an important ecosystem with distinct characteristics and adaptations. They provide opportunities for development but also cause challenges such as desertification.

Part of Geography The living world

Desertification - causes and prevention strategies

Desertification close desertification The spread of desert conditions in arid regions due to human activities, drought or climate change. is the process of land turning into desert as the quality of the soil declines over time. The main causes of desertification include:

Population growth - the population in some desert areas is increasing. In places where there are developments in mining and tourism, people are attracted by jobs. An increased population is putting greater pressure on the environment for resources such as wood and water.
Removal of wood - in developing countries, people use wood for cooking. As the population in desert areas increases, there is a greater need for fuel wood. When the land is cleared of trees, the roots of the trees no longer hold the soil together so it is more vulnerable to soil erosion close soil erosion When earth is washed or blown away. .
Overgrazing close overgrazing When land cannot sustain the number of animals that are feeding from it. - an increasing population results in larger desert areas being farmed. Sheep, cattle and goats are overgrazing the vegetation. This leaves the soil exposed to erosion.
Soil erosion - this is made worse by overgrazing and the removal of wood. Population growth is the primary cause of soil erosion.
Climate change close climate change The long-term alteration of weather patterns. - the global climate is getting warmer. In desert regions conditions are not only getting warmer but drier too. On average there is less rain now in desert regions than there was 50 years ago.

Strategies to reduce desertification

Desertification can be reduced by adopting the following strategies:

Planting more trees - the roots of trees hold the soil together and help to reduce soil erosion from wind and rain.
Improving the quality of the soil - this can be managed by encouraging people to reduce the number of grazing animals they have and grow crops instead. The animal manure can be used to fertilise the crops grown. Growing crops in this way can improve the quality of the soil as it is held together by the roots of plants and protected from erosion. This type of farming is more sustainable close sustainable An activity which does not consume or destroy resources or the environment. .
Water management - water can be stored in earth dams close earth dam A dam made of earth. Earth is used to create a circular hollow to store rain water. in the wet season and used to irrigate crops during the dry season. This is an example of using appropriate technology close appropriate technology Simple equipment and technology that the local people are able to use easily and without much cost. to manage water supplies in the desert environment.

Desertification, explained

Humans are driving the transformation of drylands into desert on an unprecedented scale around the world, with serious consequences. But there are solutions.

As global temperatures rise and the human population expands, more of the planet is vulnerable to desertification, the permanent degradation of land that was once arable.

While interpretations of the term desertification vary, the concern centers on human-caused land degradation in areas with low or variable rainfall known as drylands: arid, semi-arid, and sub-humid lands . These drylands account for more than 40 percent of the world's terrestrial surface area.

While land degradation has occurred throughout history, the pace has accelerated, reaching 30 to 35 times the historical rate, according to the United Nations . This degradation tends to be driven by a number of factors, including urbanization , mining, farming, and ranching. In the course of these activities, trees and other vegetation are cleared away , animal hooves pound the dirt, and crops deplete nutrients in the soil. Climate change also plays a significant role, increasing the risk of drought .

All of this contributes to soil erosion and an inability for the land to retain water or regrow plants. About 2 billion people live on the drylands that are vulnerable to desertification, which could displace an estimated 50 million people by 2030.

Where is desertification happening, and why?

The risk of desertification is widespread and spans more than 100 countries , hitting some of the poorest and most vulnerable populations the hardest, since subsistence farming is common across many of the affected regions.

More than 75 percent of Earth's land area is already degraded, according to the European Commission's World Atlas of Desertification , and more than 90 percent could become degraded by 2050. The commission's Joint Research Centre found that a total area half of the size of the European Union (1.61 million square miles, or 4.18 million square kilometers) is degraded annually, with Africa and Asia being the most affected.

The drivers of land degradation vary with different locations, and causes often overlap with each other. In the regions of Uzbekistan and Kazakhstan surrounding the Aral Sea , excessive use of water for agricultural irrigation has been a primary culprit in causing the sea to shrink , leaving behind a saline desert. And in Africa's Sahel region , bordered by the Sahara Desert to the north and savannas to the south, population growth has caused an increase in wood harvesting, illegal farming, and land-clearing for housing, among other changes.

The prospect of climate change and warmer average temperatures could amplify these effects. The Mediterranean region would experience a drastic transformation with warming of 2 degrees Celsius, according to one study , with all of southern Spain becoming desert. Another recent study found that the same level of warming would result in "aridification," or drying out, of up to 30 percent of Earth's land surface.

a herding family in a desertified pasture

A herder family tends pastures beside a growing desert.

When land becomes desert, its ability to support surrounding populations of people and animals declines sharply. Food often doesn't grow, water can't be collected, and habitats shift. This often produces several human health problems that range from malnutrition, respiratory disease caused by dusty air, and other diseases stemming from a lack of clean water.

Desertification solutions

In 1994, the United Nations established the Convention to Combat Desertification (UNCCD), through which 122 countries have committed to Land Degradation Neutrality targets, similar to the way countries in the climate Paris Agreement have agreed to targets for reducing carbon pollution. These efforts involve working with farmers to safeguard arable land, repairing degraded land, and managing water supplies more effectively.

The UNCCD has also promoted the Great Green Wall Initiative , an effort to restore 386,000 square miles (100 million hectares) across 20 countries in Africa by 2030. A similar effort is underway in northern China , with the government planting trees along the border of the Gobi desert to prevent it from expanding as farming, livestock grazing , and urbanization , along with climate change, removed buffering vegetation.

However, the results for these types of restoration efforts so far have been mixed. One type of mesquite tree planted in East Africa to buffer against desertification has proved to be invasive and problematic . The Great Green Wall initiative in Africa has evolved away from the idea of simply planting trees and toward the idea of " re-greening ," or supporting small farmers in managing land to maximize water harvesting (via stone barriers that decrease water runoff, for example) and nurture natural regrowth of trees and vegetation.

"The absolute number of farmers in these [at-risk rural] regions is so large that even simple and inexpensive interventions can have regional impacts," write the authors of the World Atlas of Desertification, noting that more than 80 percent of the world's farms are managed by individual households, primarily in Africa and Asia. "Smallholders are now seen as part of the solution of land degradation rather than a main problem, which was a prevailing view of the past."

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Causes and consequences of desertification in Kuwait: a case study of land degradation

Published: May 2003
Volume 62 , pages 107–115, ( 2003 )

Cite this article

Jasem M. Al-Awadhi 1 ,
Raafat F. Misak 2 &
Samira S. Omar 3

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Desertification in Kuwait is a process of environmental degradation under fragile ecological conditions and intensive human activities and the consequences of Gulf War. In Kuwait, very severe desertification prevails, due to increasing formation of new active sandy bodies, deterioration of many areas of natural vegetation cover to less than 10%, and limited water resources for large-scale forage production. Average annual desertified land in Kuwait is estimated to be 285 km 2 . In Kuwait, three indicators of land degradation are encountered. These are vegetation, soil, and surface hydrological changes. Based on field measurements of soil compaction and vegetation changes, in the west Jahra area in the northern part of the country, degradation levels were assessed. Results of these measurements show that the average infiltration rate in compacted soil decreased by 53.8% in comparison with non-compacted soil, while the average soil penetration resistance in compacted soil increased by 154.1% in comparison with non-compacted soil. The bulk density in open sites was 23.4% higher than that in protected sites. The percentage of litter in open sites decreased by 77.3% in comparison with protected sites, while the percentage of total vegetation in open sites decreased by 6.1% in comparison with protected sites.

La désertification au Koweït est un processus de dégradation de l'environnement dans un contexte de fragile équilibre écologique, d'intenses activités anthropiques et de situation d'après Guerre du Golfe. Au Koweït, une très sévère désertification progresse, due au développement de nouvelles dunes vives, à la disparition de formations végétales jusqu'à 10% de leur étendue initiale et à la limitation de la ressource en eau résultant de la réalisation de forages à grande échelle. Chaque année la désertification augmente en moyenne d'une superficie de 285 km 2 . Trois indicateurs de dégradation des terres sont identifiables. Ils sont relatifs à la végétation, aux sols et aux échanges hydrologiques superficiels. Basés sur des mesures de terrain de la compaction des sols et des changements de végétation, des niveaux de dégradation ont été évalués dans la région de Jahra au nord du pays. Les résultats de ces mesures montrent que le taux d'infiltration moyen dans les sols compactés décroît de 54%, tandis que la résistance moyenne à la pénétration augmente de 154% par comparaison avec ces mêmes sols non compactés. La masse volumique dans les sites ouverts est de 23% plus forte que dans les sites protégés. Le pourcentage de litière dans les sites ouverts diminue de 77% et le pourcentage de végétation totale de 6% par comparaison avec les sites protégés.

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Causes and Impacts of Land Degradation and Desertification: Case Study from Kazakhstan

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Department of Earth and Environmental Sciences, Faculty of Science, Kuwait University, P.O. Box 5969, 13060 Safat, Kuwait, , , , ,

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Al-Awadhi, J.M., Misak, R.F. & Omar, S.S. Causes and consequences of desertification in Kuwait: a case study of land degradation. Bull Eng Geol Environ 62 , 107–115 (2003). https://doi.org/10.1007/s10064-002-0175-0

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DOI : https://doi.org/10.1007/s10064-002-0175-0

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Desertification
Desertification in the Sahel region is a pressing environmental issue with far-reaching consequences. In this article, we will explore the causes, effects, and potential solutions to combat desertification, using a case study from the Sahel region.
Causes and Impacts of Land Degradation and Desertification: Case Study
Desertification, a phenomenon referring to land degradation in arid, semi-arid and dry sub-humid regions as a result of climatic variations and human activities, is considered as one of the most severe environmental and socio-economic problems of recent times. The principal aim of this study was to explore the impacts of desertification, degradation and drought on both the natural resources ...
Desertification
Another case study in central Senegal found degradation manifested through a reduction in species richness despite ... Accounting for this climatic variability is required before attributions to other causes of desertification can be made. For attributing vegetation changes to climate versus other causes, rain use efficiency (RUE - the ...
Causes and Impacts of Desertification in the World
Although many effects of desertification are systemically correlated with global, regional, and local climate factors, Drew lists some of these effects in the following Box.One of the great difficulties in desertification studies is that this phenomenon results from the simultaneous action of several causes in a determined area on different space-temporal scales.
Case Study: Sahel Desertification
Case Study: Sahel Desertification. What is desertification: It is the term used to describe the changing of semi arid (dry) areas into desert. It is severe in Sudan, Chad, Senegal and Burkina Faso. What are the causes: Overcultivation: the land is continually used for crops and does not have time to recover eventually al the nutrients are ...
Causes and Impacts of Land Degradation and Desertification: Case Study
The Convention to Combat Desertification in Kazakhstan was signed in 1994 and ratified in 1997. It included a number of commitments; application of integrated approach to the planning and the implementation of activities to combat desertification and its relationship with the fight against poverty; promotion of awareness and participation of the local population; encouraging the exchange of ...
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Finally, the causes of desertification are diverse but, in the majority of cases, are due to the inadequate use of land and natural resources (e.g., inappropriate management of grazing areas, land use systems, irrigation practices, deforestation, urbanization, etc.). Various efforts have been aimed toward combating desertification.
Case Studies on Desertification: Natural Resources Research XVIII
Description. The present volume reproduces edited versions of the six case studies commissioned by UNESCO and supported by UNDP, summarizes the associated case studies in a chapter, and then presents some general conclusions arising from the experience of desertification and measures to combat it.
Causes and Impacts of Land Degradation and Desertification: Case Study
"An integrated study of desertification: applications of remote sensing, GIS and spatial models in [67] Wessel, M., Agroforestry Ecosystems. Course Reader, Department of Forestry, Wageningen University. The Netherlands. 1996. [68] Glover, E. K., Tropical Dryland Rehabilitation: Case Study on Participatory Forest M anagement in Gedaref, Sudan.
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Desertification - Causes and Effects. Chapter in Book: Exploring Natural Hazards - A Case Study Approach (Eds., D. Bartlett & R.P. Singh), CRC Press, Taylor & Francis ...
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environmental change. desertification, the process by which natural or human causes reduce the biological productivity of drylands (arid and semiarid lands). Declines in productivity may be the result of climate change, deforestation, overgrazing, poverty, political instability, unsustainable irrigation practices, or combinations of these factors.
PDF Desertification Challenge : case study of Burkina Faso
Desertification Challenge : case study of Burkina Faso Presented by M. J. Tankoano PLAN OF PRESENTATION • SITUATION OF THE DESERTIFICATION OR LAND DEGRADATION • CAUSES OF DESERTIFICATION OR LAND
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Abstract. Using a meta-analytical research design, we analyzed subnational case studies (n = 132) on the causes of dryland degradation, also referred to as desertification, to determine whether the proximate causes and underlying driving forces fall into any pattern and to identify mediating factors, feedback mechanisms, cross-scalar dynamics, and typical pathways of dryland ecosystem change.
PDF Causes and Impacts of Land Degradation and Desertification: Case Study
The principal aim of this study was to explore the impacts of desertification, degradation and drought on both the natural resources and man's livelihood in the Sudan and to suggest appropriate forest resource management interventions. The study was based on a fact finding tour in the Sudan and data collection on drought trends as reflected in ...
What Has Caused Desertification in China?
Desertification is the result of complex interactions among various factors, including climate change and human activities. However, previous research generally focused on either meteorological ...
PDF Desertification
Desertification and climate change, both individually and in combination, will reduce the provision of dryland ecosystem services and lower ecosystem health, including losses in biodiversity (high confidence). Desertification and changing climate are projected to cause reductions in crop and livestock
Causes and Impacts of Land Degradation and Desertification: Case Study
abstract = "Desertification, a phenomenon referring to land degradation in arid, semi-arid and dry sub-humid regions as a result of climatic variations and human activities, is considered as one of the most severe environmental and socio-economic problems of recent times.
Causes and Impacts of Land Degradation and Desertification: Case Study
The problem of desertification is a serious threat that is causing a variety of negative social and economic effects. It is always accompanied by soil degradation as the result of human overuse of the land. During the past few decades this process has accelerated because of population growth, and the forecast is that this growth will continue to increase, which necessitates increased food ...
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Rocky desertification, a process of land degradation characterized by soil erosion and bedrock exposure, is one of the most serious land degradation problems in karst areas, and is regarded as an obstacle to local sustainable development. It is well known that human activities can accelerate rocky desertification; however, the effects of climate change on rocky desertification in karst areas ...
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Desertification, a phenomenon referring to land degradation in arid, semi-arid and dry sub-humid regions as a result of climatic variations and human activities, is considered as one of the most severe environmental and socio-economic problems o f recent times. The p rincipal aim o f th is study was to exp lore the impacts of desertification, degradation and drought on both the natural ...
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The region currently faces extensive desertification caused by numerous factors. These factors include very high birth rates and thus expansion of agriculture into unsuitable areas, uncontrolled tree cutting for a fuel, all connected with effects of climate change and bad government policies.
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Case study - the Thar Desert, Rajasthan, India; Desertification - causes and prevention strategies ... The main causes of desertification include: Population growth - the population in some desert ...
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When land becomes desert, its ability to support surrounding populations of people and animals declines sharply. Food often doesn't grow, water can't be collected, and habitats shift. This often ...
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Desertification in Kuwait is a process of environmental degradation under fragile ecological conditions and intensive human activities and the consequences of Gulf War. In Kuwait, very severe desertification prevails, due to increasing formation of new active sandy bodies, deterioration of many areas of natural vegetation cover to less than 10%, and limited water resources for large-scale ...

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Causes and Impacts of Land Degradation and Desertification: Case Study of the Sudan

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Causes and Effects of Desertification on People and the Environment

What is the process of desertification?

Where is desertification happening the most?

What causes desertification?

#1 Overgrazing

#2 Unsustainable agriculture techniques

#3 Deforestation

#4 Unsustainable water management

#5 Overpopulation and overexploitation of natural resources

#6 Urbanization and development of tourism

#7 Famine, poverty and political instability

#8 Climate change

What are the effects of desertification?

#1 Vegetation is damaged or destroyed

#2 Soil becomes infertile

#3 Soil erosion gets worse

#4 Increased vulnerability to natural disasters