Drought famine and desertification

In recent years, the world's attention has been drawn time and again to the Third World nations of Africa, by the plight of millions of people who are unable to provide themselves with food, water and the other necessities of life. The immediacy of television, with its disturbing images of dull-eyed, pot-bellied, malnourished children, skeletons of cattle in dried-up water courses, and desert sands relentlessly encroaching upon once productive land, raised public awareness to unexpected heights, culminating in the magnanimous response to the Live Aid concerts of 1985. Not unexpectedly, given the requirements of modern popular journalism and broadcasting, coverage of the situation has often

Table 3.1 Wet and dry spells in Africa south of the Sahara

Dry Wet

1680s 10th-13th centuries

1740s 1870s-m id-1890s

1750s 1920s-59 (mixed but mainly wetter)

Late-1790s-1800 1988-89



1895-1910s 1968-73 1980s 1990

Source: After Nicholson (1989)

been narrow, highly focused and shallow, lacking the broader, deeper investigation necessary to place the events in a geographical or environmental framework. For example, the present problems are often treated as a modern phenomenon, when, in fact, they are in many ways indigenous to the areas involved. The inhabitants of sub-Saharan Africa have suffered the effects of drought and famine for hundreds of years (see Table 3.1). It is part of the price that has to be paid for living in a potentially unstable environment.

Current episodes seem particularly catastrophic, but they are only the most recent in a continuing series. In dealing with the situation, the media have tended to concentrate on the problems of famine and its consequences, while most of the aid being supplied has, of necessity, been aimed at alleviating hunger. However, while famine may be the direct cause of the present suffering and hardship, it is, in reality, a symptom of more fundamental problems. Elements of a cultural, socio-economic and political nature may contribute to the intensity and duration of the famine, but, in areas such as the Sahel, the ultimate causes are to be found in the environmental problems associated with drought and desertification. The former, through its impact on plants and animals, destroys the food supply, and initiates the famine; the latter, with its associated environmental changes, causes the productive land to become barren, and ensures that the famine will persist, or at least recur with some frequency. Together, drought, famine and desertification have been implicated in some of the major human catastrophes of the past and present, and will undoubtedly contribute to future suffering and despair.


The problem of definition

Drought is a rather imprecise term with both popular and technical usage. To some, it indicates a long, dry spell, usually associated with lack of precipitation, when crops shrivel and reservoirs shrink. To others, it is a complex combination of meteorological elements, expressed in some form of moisture index (see Table 3.2). There is no widely accepted definition of drought. It is, however, very much a human concept, and many current approaches to the study of drought deal with moisture deficiency in terms of its impact on human activities, particularly those involving agriculture. Agricultural drought is defined in terms of the retardation of crop growth or development by reduced soil moisture levels. This in turn may lead to economic definitions of drought when, for example, dry conditions reduce yield or cause crop failure, leading to a reduction in income. It is also possible to define drought in purely meteorological terms, where moisture deficiency is measured against normal or average conditions, which have been established through long-term observations, such as those illustrated in Figure 3.1 (Katz and Glantz 1977).

Aridity and drought

The establishment of normal moisture levels also allows a distinction to be made between aridity and drought. Aridity is usually considered to be

Table 3.2 Examples of drought and aridity indices

Table 3.2 Examples of drought and aridity indices

Examples Famine

Source: After Landsberg (1986) Symbols P mean annual precipitation (mm) T mean annual temperature (°C) Pi individual monthly precipitation (mm) ti individual monthly temperature (°C)

P climatically appropriate water balance for existing conditions PE annual potential evapotranspiration L loss (mm)

R mean monthly recharge r number of months

Source: After Landsberg (1986) Symbols P mean annual precipitation (mm) T mean annual temperature (°C) Pi individual monthly precipitation (mm) ti individual monthly temperature (°C)

P climatically appropriate water balance for existing conditions PE annual potential evapotranspiration L loss (mm)

R mean monthly recharge r number of months

Figure 3.1 Rainfall fluctuations in five regions of Africa, 1901-87: expressed as a per cent departure from the long-term mean

Figure 3.1 Rainfall fluctuations in five regions of Africa, 1901-87: expressed as a per cent departure from the long-term mean

Reasons For Environmental Problems
Source: After Nicholson (1989)

the result of low average rainfall, and is a permanent feature of the climatology of a region (see Figure 3.2a). The deserts of the world, for example, are permanently arid, with rainfall amounts of less than 100 mm per year. In contrast, drought is a temporary feature, occurring when precipitation falls below normal or when near normal rainfall is made less effective by other weather conditions such as high temperature, low humidity and strong winds (Felch 1978).

Aridity is not a prerequisite for drought. Even areas normally considered humid may suffer from time to time, but some of the worst droughts ever experienced have occurred in areas which include some degree of aridity in their climatological makeup. Along the desert margins in Africa, for example, annual precipitation is low, ranging between 100 and 400 mm, but, under normal conditions, this would allow sufficient vegetation growth to support pastoral agriculture. Some arable activity might also be possible, if dry-farming techniques were employed. Drought occurs with considerable regularity in these areas (Le Houerou 1977). The problem lies not in the small amount of precipitation, but rather in its variability. Mean values of 100 to 400 mm are based on long-term observations, and effectively mask totals in individual years, which may range well above or below the values quoted (see Figure 3.3). Weather records at Beijing, in drought-prone northern China, show that the city receives close to 600 mm of precipitation in an average year. However, the amount falling in the wetter years can be 6-9 times that of the drier years. Only 148 mm were recorded in 1891, for example, and 256 mm in 1921, compared to a maximum of 1,405 mm in 1956 (NCGCC 1990). Rainfall variability is now recognized as a major factor in the occurrence of drought (Oguntoyinbo 1986), and a number of writers have questioned the use of 'normal' values in such circumstances. In areas of major rainfall variability the nature of the environment reflects that variability rather than the so-called normal conditions, and any response to the problems which arise from drought conditions must take that into account (Katz and Glantz 1977).

Some researchers claim that the drought in sub-Saharan Africa has been intensifying as a result of climatic change. Bryson (1973), for example, has identified changes in atmospheric circulation patterns which could intensify and prolong drought in the Sahel. There is, however, no conclusive evidence that the current drought is anything other than a further indication of the inherent unreliability of precipitation in the area (Nicholson 1989).

The human response to drought

Each generation has its images of drought. In

Figure 3.2a The deserts and arid lands of the world

What Causes Drought The Sahel
Source: Compiled from various sources

Figure 3.2b Areas at risk from desertification

Figure 3.2b Areas at risk from desertification

Desertification 1980
Source: Compiled from various sources

the 1990s it is East Africa; in the 1980s it was Ethiopia; in the 1960s it was the Sahel; in the 1930s it was the Dustbowl, described with such feeling by John Steinbeck in The Grapes of Wrath. Although these have gripped the popular imagination, they are only the more serious examples of perhaps the most ubiquitous climatological problem that society has to face, Drought strikes areas as far apart as Australia and the Canadian Prairies, or southern Africa and the China, with some regularity, often with considerable severity, and with an impact that is

Figure 3.3 Variability of precipitation at selected stations in Africa

Figure 3.3 Variability of precipitation at selected stations in Africa

Source: Compiled from data in Landsberg (1986)

felt beyond the areas directly affected. Drought is expected in such areas, but elsewhere it is highly irregular and, as a result, all the more serious. Such was the case in 1976 when the normally humid UK was sufficiently dry that the government felt it necessary to appoint a Minister of Drought.

Drought may also have played a significant role in the historical development of society through its impact on past civilizations. For example, changes in wind circulation and increased aridity in what is now northern Syria from about 2200 BC are thought to have destroyed the agricultural base of the Mesopotamian Subir civilization (Weiss et al. 1993), and the decay of the Harrapan civilization in the Indus valley has been linked to the desiccation of that region after 1800 BC (Calder 1974). In Europe, some 3000 years ago, the flourishing Mycenaean civilization of southern Greece went into irreversible decline. The rapidity and extent of the decline was such that it was commonly attributed to the invasion of Mycenae by Greeks from the regions to the north. In 1968, however, Rhys Carpenter reassessed the available evidence, and suggested that no invasion had taken place. Instead, he postulated that drought followed by starvation, social unrest and migration led to the downfall of the Mycenaeans. Climatologists at the University of Wisconsin-Madison developed Carpenter's theory further, and concluded that drought was a major contributory factor in the decay of the civilization (Bryson et al. 1974; Bryson and Murray 1977). As in many cases where a climatic explanation is invoked to account for major societal changes in the distant past, the link between the decline of the Mycenaean civilization and drought is not considered convincing by some researchers (see e.g. Parry 1978). The absence of adequate and appropriate data prevents such hypotheses from being developed much beyond the speculative stage.

Modern views of drought vary with time and place and with the nature of the event itself. It may be seen as a technological problem, an economic problem, a political problem, a cultural problem or sometimes a multi-faceted problem involving all of these. Whatever else it may be, however, it is always an environmental problem, and basic to any understanding of the situation is the relationship between society and environment in drought-prone areas.

Over thousands of years, certain plants and animals have adapted to life with limited moisture. Their needs are met, therefore no drought exists. This is the theoretical situation in most arid areas. In reality, it is much more complex, for although the flora and fauna may exist in a state of equilibrium with other elements in the environment, it is a dynamic equilibrium, and the balance can be disturbed. Changes in weather patterns, for example, might further reduce the already limited amount of precipitation available, changing the whole relationship. If the plants and animals can no longer cope with the reduced water supply, they will suffer the effects of drought. Depending upon the extent of the change, plants may die from lack of moisture, they may be forced out of the area as a result of competition with species more suited to the new conditions or they may survive, but at a reduced level of productivity. The situation is more complex for animals, but the response is often easier. In addition to requiring water, they also depend upon the plants for food, and their fate, therefore, will be influenced by that of the plants. They have one major advantage over plants, however. Being capable of movement, they can respond to changing conditions by migrating to areas where their needs can be met. Eventually some degree of balance will again be attained, although certain areas—such as the world's desert margins—can be in a continual state of flux for long periods of time.

The human animal, like other species, is also forced to respond to such changing environmental conditions. In earlier times this often involved migration, which was relatively easy for small primitive communities, living by hunting and gathering, in areas where the overall population was small. As societies changed, however, this response was often no longer possible. In areas of permanent, or even semipermanent agricultural settlement, with their associated physical and socio-economic structures, migration was certainly not an option—indeed, it was almost a last resort. The establishment of political boundaries, which took no account of environmental patterns, also restricted migration in certain areas. As a result, in those regions susceptible to drought, the tendency, perhaps even the necessity, to challenge the environment grew. If sufficient water was not available from precipitation either it had to be supplied in other ways—by well and aqueduct, for example—or different farming techniques had to be adopted to reduce the moisture need in the first place. The success of these approaches depended very much on such elements as the nature, intensity and duration of the drought, plus a variety of human factors, which included the numbers, stage of cultural development and technological level of the peoples involved.

Types of drought

C.W.Thornthwaite, the eminent applied climatologist, whose pioneering water balance studies made a major contribution to the understanding of aridity, recognized four types of drought, defined in terms of agricultural requirements (Thornthwaite 1947). These were permanent, seasonal, contingent and invisible drought. Agriculture is not normally possible in areas of permanent drought, since there is insufficient moisture for anything but the xerophytic plants which have adapted to the arid environment. Crops can be produced in such areas, but only at great expense or under exceptional circumstances such as those which apply to the Israeli activities in the Negev Desert, for example (Berkofsky 1986). On the margins of the world's great deserts, there are regions of seasonal drought, where arid conditions prevail for part of the year, but which are balanced by a distinct wet season. Much of India, the Sahel and the southern parts of Africa experience such seasonal drought. Agriculture is carried out, often very successfully, during the wet season, and even during the dry season, if the moisture from the preceding rainy season can be retained. If for some reason the rainy season is curtailed, however, the potential for drought is great, and it is not surprising that areas such as the Sahel and the Indian sub-continent have experienced some of the world's most spectacular and catastrophic droughts. The problem is intensified in drier years by the irregularity with which the rains fall, making planning difficult, if not impossible.

Irregular and variable precipitation is also characteristic of contingent drought. In Thornthwaite's definition, this is experienced in areas which normally have an adequate supply of moisture to meet crop needs. Serious problems arise because the agricultural system is not set up to cope with unpredictable and lengthy periods of inadequate precipitation. The interior plains of North America have suffered from contingent drought for hundreds of years, and the droughts of 1975-76 and 1988-92 in Britain would fit this category also.

The presence of these three types of drought is indicated by physical changes in the soil and vegetation in the areas affected, but there is also a fourth type which is less obvious. This is the so-called invisible drought, which often can be identified only by sophisticated instrumentation and statistical techniques. The crops appear to be growing well, even to the experienced observer, and there is no obvious lack of precipitation. However, moisture requirements are not being met, the crop is not growing at its optimum rate, and the potential yield from the land is reduced.

America Future Desertification

Figure 3.4 Sample climatic water budget for a mid-latitude station in North-America or Europe, based on the Thornthwaite model

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  • chanelle
    What is famine and desertization?
    5 years ago
  • azelio
    Which did not contribute to the famine in the african sahel in 1974?
    8 years ago
  • jens
    What is relationship between famine and desertification?
    8 years ago