Desertification

11 Key excerpts on "Desertification"

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  Deserts and Desert Environments

  • Julie J Laity(Author)
  • 2009(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  13 Desertification AND THE HUMAN DIMENSION 13.1 D ESERTIFICATION: INTRODUCTION AND TERMINOLOGY Desertification refers to changes in dryland produc-tivity, stability, and species composition. The term was first employed by Lavauden (1927) and Aubre-ville (1949), who used it to describe the transforma-tion of productive land into desert as a result of human activity in Africa (Le Houérou 2002). Renewed interest in the concept of Desertification resulted from a series of droughts and famines in the Sahelian region that began in the late 1960s (Herrmann & Hutchinson 2005). In its present usage, Desertification is a poorly defined term, with many shades of meaning (Thomas & Middleton 1994). Inconsistency in terminology reflects an incomplete understanding of the causes and nature of change, and a lack of agreement as to the permanence and endpoints of ecosystem disruption. Desertification is difficult to determine in part because there is an absence of measurable criteria. In general, the term Desertification has been used to describe conditions of decreasing productivity and long-lasting, possibly irreversible, desert-like condi-tions. The United Nations Environment Program (1992) defined Desertification as “land degradation in arid, semiarid and dry sub-humid areas resulting from various factors including climatic variations and human activities.” Mainguet (1991) concluded that Desertification “is the ultimate step of land degrada-tion: irreversibly sterile land, meaning irreversible in human terms and within practicable economic limitations.” A distinction is often made between desertifica-tion and degradation. The terms Desertification and desertization imply an expansion of desert-like con-ditions to regions that climatically would not be clas-sified as desert.

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  Biological and Environmental Hazards, Risks, and Disasters

  • Ramesh Sivanpillai, John F. Shroder(Authors)
  • 2015(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 11.1

  Desertification

  John Oswald,  and Sarah Harris     Department of Geography and Geology, Eastern Michigan University, MI, USA

  Abstract

  Desertification, an intentionally foreboding term, is at its core land degradation in dryland environments. After nearly 40  years of international attention, the analysis of the causes and consequences of land degradation in dryland systems remains shrouded in the nuanced complexities of multiple interwoven variables (biophysical, anthropogenic, and climatic) working simultaneously to bring about change in these ecologically and socially vulnerable areas. In order to fully grasp the complexities of Desertification, this chapter follows a fivefold approach. First, it provides a synthesis of the history and politicization of the term. Second, it establishes Desertification's geospatial context. Third, it identifies the interrelated drivers of land degradation and their impacts, with special focus placed on North Africa, the Middle East, and Central Asia. Fourth, it outlines the current approaches to studying land degradation and Desertification. Finally, it concludes by situating the Desertification dynamic in the context of sustainability and poverty eradication.

  Keywords

  Central Asia; Desertification; Drylands; Land degradation; Middle East; North Africa; Poverty eradication; Remote sensing; Sustainability

   

  Desertification, an intentionally ominous term, is a complex and multilayered phenomenon that simultaneously denotes both the process of landscape transformation, as well as the end state of degradation in dryland ecosystems (arid, semiarid, and dry-subhumid regions). As discussed in greater detail below, Desertification as a process includes the combination of anthropogenic, biophysical, and climatic inputs that negatively impact these highly adapted, yet vulnerable, ecosystems around the world. Within these increasingly hydrologically stressed dryland regions, traditionally marginalized populations (ecologically, economically, and politically, or what Reynolds et al. (2007) term the “dryland syndrome”) living in these areas face increasing challenges in their ability to produce food, generate income, and maintain their traditional lifestyles. As population numbers, currently at two billion people (MEA, 2005

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  The Threatening Desert

  Controlling desertification

  • Alan Grainger(Author)
  • 2013(Publication Date)
  • Routledge

    (Publisher)

  1 • What Is Desertification?

  Desertification is the degradation of lands in dry areas. This chapter opens with a review of some key definitions of Desertification, briefly describes the general distribution of drylands and the reasons for their occurrence, distinguishes between Desertification and natural desert, and then introduces the two main physical characteristics of Desertification - the degradation of soil and vegetation. Desertification is not the desert expansion of popular imagination. Instead it is essentially a subtle, dispersed and continuous process which mainly occurs far away from desert fringes, with the outright conversion of fertile land into desert only taking place in extreme cases.

  The direct cause of Desertification is poor land use. A long-term change in climate could make an area more desert-like without human intervention, but so far there is no firm evidence that this is taking place. Poor land use is not unique to dry areas, and consequently soil erosion and the removal of vegetative cover are major problems throughout the tropics. However, it is the severe environmental and human effects and the influence of low and erratic rainfall which make Desertification such a distinctive and worrying problem. There are four main types of poor land use in the drylands: overcultivation, overgrazing, mismanagement of irrigated cropland and deforestation. These are briefly reviewed here as a prelude to a more detailed discussion in Chapter 2, and some examples are also given of Desertification in the civilizations of the ancient world. The role of climate is then examined in detail. At UNCOD, with no evidence of long-lasting climatic change in the Sahel or other seriously affected areas, Desertification was viewed as a long-term process of degradation which merely accelerated during occasional periods of intense drought. Since then, however, the drought in the Sahel has continued, and there is a growing recognition that global climate could be changing or about to change. So it is time for a reappraisal of the role of climate in Desertification.

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  The Turning Points of Environmental History

  • Frank Uekötter, Frank Uekotter, Frank Uekötter(Authors)
  • 2010(Publication Date)
  • University of Pittsburgh Press

    (Publisher)

  10 10 Desertification A L O N TA L • Desertification is among the most misunderstood— and the most neglected—of the world’s global environmental challenges. Images of irrepressible waves of sands overwhelming civilization are not entirely ficti-tious. Indeed, the spectacle can be witnessed every day from the Sahara to China; frequently, natural phenomena can lead to Desertification. 1 For the most part, however, Desertification refers to the much less dramatic but far more pernicious steady decrease in land productivity that takes place in drylands. It is important to emphasize another misconception. Although they may contain productive oases or river valleys, true deserts (arid and hyperarid lands) are typically not the areas in which Desertification on a large scale takes place. Rather, it is in the semiarid and subhumid drylands that receive low, often seasonable rainfall and support soils with modest organic content, where the relatively low-land produc-tivity may decline even further. When the nations of the world finally negotiated a treaty to “combat” deserti-fication in 1994, they defined the phenomenon as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities.” 2 A higher resolution definition put forward by the United Nations Environmental Program (UNEP) characterizes desertifica-tion by five processes that damage land productivity: (1) vegetation degradation, (2) water erosion of soils, (3) wind erosion of soils, (4) soil salinization, and (5) soil compaction—in the drylands. Natural shifts in climate or meteorological j . r . m c n e i l l processes can surely contribute to these processes. For example, geologists be-lieve that the change in wind directions after the Holocene period replaced the plentiful deposition of Sahara loess in Israel’s Negev Desert, with smaller quanti-ties that arrived from Saudi Arabia.

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  Remote Sensing of Natural Hazards

  • Jay Gao(Author)
  • 2023(Publication Date)
  • CRC Press

    (Publisher)

  5 Land Desertification

  DOI: 10.1201/9781003354321-5

  5.1 INTRODUCTION

  Desertification, also known as desertization, is a natural process in which the original natural-looking, productive land is converted to desert-like dryland. This conversion is usually accompanied by an increase in mobile dunes, a decrease in surface vegetation, or complete elimination of vegetative cover in the worst scenario. As an extreme form of land degradation, Desertification signifies the complete loss of land capability for sustainable farming, grazing, or forestry. In most cases, this loss is irreversible or faces a grim prospect of reversibility. Desertification usually takes place in arid, semi-arid, and dry sub-humid regions of the world where the environment is fragile and vulnerable to external changes. Desertification is caused by natural processes (e.g., droughts and climate change) or inappropriate human activities, such as deforestation, exploitative tillage practice, land reclamation, and overgrazing in semi-arid grassland areas (Figure 5.1 ). The major driving forces, both natural and anthropogenic, of Desertification in the Arab region are outlined in Figure 5.2 , together with the manifestation of Desertification. Most of them are also applicable to other arid and semi-arid regions of the world.

  FIGURE 5.1

  Factors leading to Desertification and their interactions. (Source: Modified from Perez-Trejo, 1994 .)

  FIGURE 5.2

  Major driving forces of Desertification, their manifestations, and impacts in the Arab region. (Source: Abahussain et al., 2002 . Used with permission.)

  Desertification is considered a semi-natural hazard that threatens the livelihood of farmers and pastoralists, and the environment. This process of change exerts a profound impact not only on the local environment but also on the living conditions in distant areas. During Desertification, land fertility is reduced via the deposition of sand blown from elsewhere or the depletion of fine fertile soil particles by wind, leading to deteriorated land productivity. If exacerbated by drought, Desertification can result in crop failures. In the worst case, the encroachment of the advancing dunes shrinks arable land and reduces the fertility of the affected farmland to such a level that it is no longer profitable to farm, leading ultimately to farmland abandonment. Moreover, the newly desertified land serves as a sand source to fuel dust storms that degrade air quality and disrupt aviation. The Desertification of shrubland reduces biodiversity. Therefore, it is very important to study Desertification and monitor its temporal evolution. Accurate assessment of the status, changing trend and rate of Desertification is a prerequisite to enacting effective measures to combat the advance of dunes, reverse the degradation process, and rehabilitate the desertified land to productive uses. Since the United Nations Conference on Desertification in 1977, tremendous progress has been made in studying Desertification by means of remote sensing.

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  Management of Problem Soils in Arid Ecosystems

  • A. Monem Balba(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  3 ).

  Doubts that climatic changes are the sole reason of desert expansion had started. Another concept emerged since the 1960s to explain the expansion of desert. It implies that this phenomenon is a result of human activities as well as natural extreme events (Stump4 ). In this period the terms Desertification and desertization became common.

  The term Desertification was first used but not formally defined by Aubreville5 in 1949 as stated by Goudie.2 Kovda6 introduced the term “land aridization” to mean several processes and trends that reduce the effective moisture content over large areas and decrease the biological productivity of the soils and plants of the ecosystem.

  A definition of Desertification adopted by the Desertification Map of the World (UNEP/FAO/UNESCO/WMO7 ) is: “the intensification or extension of desert conditions. It is a process leading to reduced biological productivity with consequent reduction in plant biomass as in the lands carrying capacity for livestock, in crop yields and human well being.” Another definition adopted by the UN Desertification Conference,8 states that “Desertification is the diminution or destruction of the biological potential of the land which leads ultimately to desert-like conditions.”

  Dregne’s9 definition of Desertification emphasized the role of man’s activities as follows:

  “Desertification is the impoverishment of terrestrial ecosystems under the impact of man.” It is the process of deterioration in these ecosystems that can be measured by reduced productivity of desirable plants, undesirable alterations in the biomass and the diversity of the micro and macro-fauna and flora, accelerated soil deterioration and increased hazards for human occupancy. Sabadell et al.10

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  Human Impact on Environment and Sustainable Development in Africa

  • Michael B.K. Darkoh, Apollo Rwomire(Authors)
  • 2018(Publication Date)
  • Taylor & Francis

    (Publisher)

  et al., 1991).

  Most current definitions include some mention of land degradation, the loss of productivity, the combined roles of climate and human activity, and the fact that Desertification is restricted to drylands. But these definitions are too general for estimating the actual extent and degree of Desertification in a particular area. Most in common use are criticized for their vagueness on key issues (is it a process or a state?; are processes like deforestation and salinization causes or symptoms?; what exactly is the role of drought?).

  The latest and most widely accepted definition is the internationally negotiated one which defines Desertification as land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities (UNCED, 1992). In the context of this new definition, as in previous definitions proposed by UNEP and others (see Odingo, 1990), land is taken to mean the terrestrial bio-productive system that comprises soils, vegetation, other biota and the ecological and hydrological processes that operate within the system.

  Degradation implies diminution or destruction of the biological potential (resource potential) by one or a combination of processes acting on the land. The concept of land degradation is broader than soil degradation since it deals with the whole ecosystem in which soil is just one of the components. The processes of land degradation include water erosion, wind erosion and sedimentation by these agents, long-term destruction of vegetation and diminution of many plants and animal populations, or decreases of crop yields where relevant, and salinization or sodication of soils. The 1994 UN International Convention to Combat Desertification described land degradation as the reduction or loss of the biological or economic productivity and complexity of the land (INCD, 1994). Human activities include overcultivation, overgrazing, deforestation, poor irrigation practices and any other inappropriate land use practices.

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  Climate Change in Deserts

  Past, Present and Future

  • Martin Williams(Author)
  • 2014(Publication Date)
  • Cambridge University Press

    (Publisher)

  This is very clearly reflected in the thoughtful editorial discussion of climatic fluctuations by Middleton and Thomas in the second edition (UNEP, 1997). 476 Desertification: causes, consequences and solutions It is also worth noting that a number of workers reject the very notion of deser- tification as defined by international organisations such as UNEP, arguing that local farmers are far more in tune with environmental fluctuations than outside agencies are willing to acknowledge and that they show a high degree of resilience and a considerable capacity to adapt to change (Bassett and Crummey, 2003). In addition, there is good evidence in support of ‘natural Desertification’, that is, land degradation caused by a sequence of geomorphic processes initiated, directly and indirectly, by long-term changes in climate that have nothing to do with human activities (Avni, 2005; Avni et al., 2006; Avni et al., 2010). We will consider these studies first before evaluating the impact of human activities on the landscapes of deserts and their margins. The manifestations of dryland degradation or Desertification are as varied as the individual causes (Table 24.1), indicating that it would be naive to seek a single cause. A potentially useful approach would be to examine a number of examples drawn from different parts of the desert world in order to learn from history and see if we can identify any general prerequisites for achieving optimum land use in arid lands. This chapter seeks to do that. 24.2 Natural Desertification Gully erosion has been widely considered as one of the more obvious signs of accel- erated soil loss brought about by human mismanagement, and it is not hard to find apparently convincing evidence of such processes in many parts of the desert world. However, a degree of caution is advisable before attributing the cause of gully erosion to human actions.

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  Diversity of Ecosystems

  • Mahamane Ali(Author)
  • 2012(Publication Date)
  • IntechOpen

    (Publisher)

  While trying to escape from desert, the wilderness pursues them with their practices in land use (UNCCD, 2004; Henson, 2008, Barua et al., 2010). Thus, poor people become both the cause and the victims of land degradation (Günter et al., 2009). For Mexico, the regulation of the General Law for Sustainable Forest Development defines Desertification as the loss of productive capacity of land caused by nature or man in any ecosystem (DOF, 2005). Although this definition assumes the concept completely, it is worth contrasting it with the one used by the United Nations Convention to Combat Desertification (UNCCD) which reads: Land degradation in arid, semiarid and subhumid lands, is the loss of biological or economic productivity and complexity of agriculture (irrigation and temporal), pastures, woods and forests that results from a process or combination of processes including those promoted by the man such as: a) water or wind erosion, b) deterioration of physical, chemical and biological soil properties and) the permanent loss of vegetation. This definition is used worldwide to describe Desertification and its impacts (Grainger et al., 2000). Diversity of Ecosystems 168 Causes of Desertification vary worldwide. These can be divided into two groups (Geist & Lambin, 2004), 1) those that predispose Desertification called underlying causes and 2) those that physically start a Desertification process, called proximate causes. Among underlying causes are climate, economics, institutions, national policies and remote influences of population growth. While proximate causes include the expansion of agriculture, overgrazing and infrastructure development. Climate variability represented by meteorological phenomena acts concomitantly and synergistic with other drivers. magnitude of storms or duration of droughts can also be drivers to start Desertification process.

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  Exploring Natural Hazards

  A Case Study Approach

  • Darius Bartlett, Ramesh Singh(Authors)
  • 2018(Publication Date)
  • Chapman and Hall/CRC

    (Publisher)

  7 Desertification Causes and Effects Amal Kar

  7.1 Introduction

  7.2 Defining Desertification

  7.3 Recent Paradigms of Desertification

  7.4 Desertification Concept at the Un Convention to Combat Desertification (UNCCD)

  7.5 Desertification Processes

  7.5.1 Biophysical Processes

  7.5.2 Socioeconomic Processes

  7.6 Proximal Causes and Effects of Desertification in the Thar Desert

  7.6.1 Traditional Agriculture and Land Management Practices

  7.6.2 Effects of Population Pressure on Pasture Conditions

  7.6.3 Ushering in the Green Revolution through Groundwater Irrigation and Tractor Use

  7.6.4 Learning from Past Mistakes and Adoption of Management Practices

  7.6.5 Other Emerging Factors of Degradation

  7.6.6 Lessons Learnt and the Way Forward in View of Global Warming

  7.7 Linking the Biophysical and the Socioeconomic Processes

  7.7.1 The D-P-S-I-R Concept

  7.7.2 Modeling of D-P-S-I-R

  7.8 Towards a Common Monitoring and Assessment Method

  7.8.1 Global Estimates of Desertification

  7.8.2 Twenty-First Century Assessments

  7.8.3 Recent Desertification Mapping in India

  7.8.4 Recent Mapping in China

  7.9 From Desertification to Land Degradation Neutrality and Zero Net Land Degradation

  7.10 Conclusion and Perspective

  References

  7.1 Introduction

  The word ‘Desertification’ brings immediately to the mind the images of an expanding desert, advancing sand dunes and an overall barren landscape. Desertification is not, however, about expanding boundaries of an existing desert, but about land degradation in the arid, semi-arid and dry sub-humid regions, that results from various factors, including climatic variations and human activities (UN, 1992; UNCCD, 1995). It is a slow and less perceptible process that is expected to gradually lead to the loss of land’s biological and economic productivity and complexity (UNCCD, 1995), and thus affect the socioeconomic conditions of people whose livelihoods depend on that land. The three climatic regions mentioned above, together with the hyper-arid regions, form the drylands, which cover about 41% of Earth’s land surface and are inhabited by more than 2 billion people (Safriel and Adeel, 2005). Figure 7.1

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  Arid Lands

  Today And Tomorrow

  • Charles Hutchinson(Author)
  • 2019(Publication Date)
  • Routledge

    (Publisher)

  Since dryland vegetation is often ephemeral in time and space, the tendency is to focus on local scale changes rather than to view each land facet in a broader regional context. At the larger scale, the system may be more stable and/or more resilient if the time dimension is extended than the often spectacular local examples of degradation would suggest. With the emergence of large-area surveillance systems (7, 8, 9), the robust nature of arid ecosystems may receive more attention, but to date it is their inability to withstand concentrated human use in time and space that has attracted the greatest attention. Even where human actions are identified as constituting the primary source of degradation, a number of researchers argue that it is the inability of human systems to recognize and to adapt to the underlying morphodynamic processes characteristic of dryland ecosystems that promotes undesired change (1 0, 11). Moreover, it is relatively easy for the analysts of physical and biological systems to identify indicators of unwanted alterations (12). These indicators can be traced to definite causes, and precise prescriptions for remedial measures can usually be identified. such suggestions are often tied to carrying capacity limits that are based on cautious assessments of biological productivity and on a preference for maximizing standing biomass. Invariably the concern is with maintaining high quality resource potential for the longest possible time. Efforts to generate greater productivity are viewed as doomed to failure in the long run if these efforts exceed the inherent carrying capa-city for a substantial period of time. Humans feature in this perspective largely as misguided or perverse destroyers of a natural world that could sustain them if greed and shortsightedness did not all too frequently promote wasteful practices that mine and degrade dry land productivity.

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