Chapter 7 New Developments in Desertification (September 1993)
"The future of life on earth was once entirely beyond human control. We lived for most of our time on this planet as one species among many, depending on natural processes that functioned without our intervention. Today the future of life on earth depends on human action. At no time during the last hundred thousand years has the survival of the human species along with most other species been so imperiled. We have reached this state through an overwhelming increase in human numbers, made possible through our growing command of energy resources that we have used to modify the surface of the earth" Dasmann (1984).
1. Desertification, a Fluctuating Concept
The word desertification describes a fluctuating concept but may have a basic simple meaning: the degradation which introduces desert-like conditions or transforms an ecosystem into a desert-like landscape.
It acquired its patent of gentility when Aubreville (1949) used it - without defining it - for the first time (p. 6) and observed: "Ce sont de vrais deserts qui naissent aujourd'hui sous nos yeux dans des pays OU il tombe annuellement de 700 a plus de 1500 mm de pluies. "(Real deserts appear today under our eyes in areas where the annual rainfall is between 700 and 1500 mm.) This sentence of Aubreville is not premonitory or intuitive; it results directly from field observations. He, of course, thought of desertification as human-induced vegetation degradation and soil erosion following shifting cultivation in the humid tropics, and more precisely here the Sahelo-Sudanian ecosystem of the northern former Oubangui-Chari (at present Republic of Central Africa).
When at the end of the 1970s the ecological crisis reached south of the Sahara, in the Sahel, its first towering acme, UNCOD, proposed in 1977 a map of areas at risk of desertification from varying degrees and a comprehensive definition (p.7, resolution number 7), which was propagated by the mass m(Xlia: "Desertification is the diminution or destruction of the biological potential of the land, and can lead ultimately to desert-like conditions. It is an aspect of the widespread deterioration of ecosystems, and has diminished or destroyed the biological potential, i.e., plant and animal production, for multiple use purposes at a time when increased productivity is needed to support growing populations in quest of development."
In spite of this UN definition, the numerous observations made in different regions ended in the multiplication of the definitions which may all be classified in five categories, namely:
1. The spread of desert-like landscapes budding from the deserts with the wrong idea of encroaching desert.
2. The spread of exacerbated mechanisms of land degradation, characteristic of deserts (wind erosion, water erosion) in the semi-arid and dry subhumid ecosystems.
3. The decrease in the biological productivity of land. This is the sense given by Dregne (1983): "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 alteration in the biomass and the diversity of the micro and macro fauna and flora, accelerated soil deterioration, and increased hazards for human occupancy." Olsson (1985) adds a notion of time scale: "The long-term decrease of the lands biological productivity caused or accelerated by human activities in combination with the climate."
4. Degradation of the social and economic conditions. This was already introduced by Kates et al. (1977), who wrote: "It involves destructive processes in which the productive base oeteriorates and the social system is imperilled. Unlike drought, which is usually a short-term diminution of a available moisture, the physical processes involved in desertification are long-term, chronic, and pervasive."
Impoverishment of the social system has also been developed by Warren and Maizels (1977). They introduced in the definition the idea of a sustained economic impact, namely a decline in the yield: "A simple graphic meaning of the word desertification is the development of desert-like landscape in areas which were once green. Its practical meaning ... is a sustained decline in the yield of useful crops from a dry area accompanying certain kinds of environmental change, both natural and man induced."
5. The ultimate nonproductive desert-like and irreversible status of a deteriorated environment. "Desertification is the name given to the processes whereby such ecosystems lose this capacity to revive or to repair themselves" (Hare 1985). Hare introduces the idea of natural irreversible deterioration.
This dispersion is not satisfactory. In resolution 441172 of December 1989 the United Nations General Assembly asked UNEP to undertake a general reevaluation of desertification to be discussed at the United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992.
The Third Meeting of the Technical Advisory Group on Desertification Assessment and Mapping, covened by UNEP, 5-7 June 1991, proposed the following definition: "Desertification is land degradation in arid, semi-arid and dry subhumid areas resulting mainly &om adverse human impact."
It is assumed that within the context of the above definition, land implies a declining of the crop, deteriorating vegetative cover, exacerbation of external dynamics at the land surface, qualitative and quantitative retrogression of water resources, degrading soils and pollution of the air. Degradation is a point of evolution which leads to reduction of the resource potential.
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Taking into account this definition, the special session of the UNEP Governing Council, held in Nairobi (3-5 February 1992), summarized the impact of land degradation as follows: " ... about 73 per cent of the rangelands, 47 per cent of the rainfed croplands and 30 per cent of the irrigated lands in the drylands, thus affecting more than 3.6 billion hectares of the total world area of arid, semiarid and dry sub-humid lands, or about 25 per cent of the total world~and area and about 900 million people, or one sixth of the world population" and" ... the impact of desertification on Africa in particular where it is a serious contributory factor to famines, such as those which occurred in 1984 and 1985, affecting between thirty million and thirty-five million people, and in 1991, when some thirty million people were threatened by famine and needed urgent external food aid in order to survive." "Desertification is a global phenomenon directly affecting more than 60 per cent of the countries of the world."
The 1991 UNEP definition of desertification, which insists on man-induced causes of desertification, was discussed and amended by UNCED in Rio de Janeiro (Brazil) in June 1992. UNCED, after international negotiations, adopted the following definition: "Desertification is land degradation in arid, semi-arid and dry subhumid areas resulting from various factors including climatic variations and human activities." After Rio, the United Nations General Assembly resolution 47/188 decided to organize a followup and established an Intergovernmental Negotiating Committee to elaborate an International Convention to Combat Desertification (INeD) by June 1994. The first (of five) negotiating session of this Committee to combat desertification in those countries experiencing serious droughts and/or desertification, particularly in Africa, took place in NairobiinJune 1993.
The UNCED definition determined in Rio de Janeiro is justified. The meteorological data obtained at the beginning of the 1970s registered a climatic break with a decrease of rainfall in the southern latitudes, mainly in the tropical drylands but also in the monsoon and western winds ecosystems where rainfall became more irregular, and a noticeable warming in the higher latitudes. In Africa between 1951 and 1973 the 500 mm/year isohyet had shifted by 3° towards the south (CarbonneI1993, unpubl.; Fig. 85). This phenomenon is considered as independent of human-kind but its environmental effects are aggravated by the demographic increase.
After the publication of the first edition of this book (1991), the greatest reserve which appeared was at the level of the statement (p. 16) that desertification means "irreversibly sterile land". Unfortunately, the latest UNCED definition does not answer this question. Neither the notion of degrees of land degradation nor the ultimate degree when land degradation becomes irreversible, which should be the usual meaning of desertification, are mentioned. In practice, the degree of land degradation may be considered as irreversible when seeds have disappeared from the soil or when, according to Dregne (1983), the soil is degraded to such a point that the seeds in the soil cannot germinate because the soil has lost its ability to conserve humidity .
We wish to state again that, according to field observations, the notion of irreversibility has a double content, of time and of economy:
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Of time: when introducing the idea of irreversibility in desertification we introduce simultaneously the idea of a time scale; irreversibility could correspond to one human generation, 25 years. The generation which stands desertification is not able to repair it. Rehabilitation, if possible, is the task of several future generations. Of economy: in Texas and New Mexico, in Tunisia, and in the Chinese deserts the degradation by wind results in the same hummock blow-out conditions. The degradation can be called "economically irreversible" because it would take large and expensive machinery to level the hummocks and restore the land to its original smooth conditions. And we are not sure that this will lead to successful results because it would disturb the sand structure and cause it to become a friable material that is easily deflated.
The expression "green desertification" was proposed and means the substitution, during all the stages leading to desertification, of a nonpalatable vegetation that is economically not interesting for a very useful edible one.
If the concept of desertification is synonymous with land degradation, it must be considered as the most important environmental problem of the world today. If the concept contains the idea of irreversible land degradation, i.e., the end of a chain of transformations which lead an area to become a sterile desertlike area with desert-like conditions, this status is almost nonexistent. According to Dregne (1983), only tiny areas of the planet are affected; Dregne's assessment isO.2%.
In Africa, the semi-arid ecosystem of Khordofan was considered one of the most degraded areas. Olsson (1985) performed a satellite-based monitoring of the desertification in eastern Khordofan and observed that "signs of desertification can mainly be seen during extremely dry periods ... It has not been possible to"find a consistent trend of degrading landscape".
In her study of fuelwood resources and land degradation in the same area, Olsson (1985) confirms this absence of desertification "no woody species seemed to have been eradicated from the area, no ecological zones had shifted southwards and the boundaries between different vegetation associations appear to be same as they were 80 years ago" .
In China, drought and land degradation have been recognized by the Chinese as a problem for at least two millenia. The destructive process of environmental degradation is mainly contemporaneous with socio-economic disturbances and political upheavals aggravated by droughts (Zhu Zhenda and Liu Shu 1983).
Toulmin (1988), returning from the semi-arid regions of Mali, had the pleasure to describe recovering greening areas.
This shows the fundamental necessity of differentiating between land degradation, which can be solved, and desertification, which to be solved requires expansive or sophisticated techniques that are often economically too luxurious for the people inhabiting the area.
After obtaining a satisfactory definition, a second question arises:
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2. What is Really Going on?
Three levels should be considered: causes, mechanisms, and impact on the environment and on socio-economic structures. The main controversy, however, concerns the causes, which are numerous and intricate. They can be classified as follows:
7.1 Natural Causes: Droughts Since the Beginning of the Century
In the 20th century the Sahel has suffered four droughts in 1900-1903, 1911-1920, 1939-1944, and 1968-1985, with the maximum deficit in 1972-1973 and 1982-1984. In total there have been 47 deficit years between 1900 and 1990. The drylands in China had the same year-on-year variations and runs of dry years as did the Sahel from 1900 to 1909, 1913 to 1930 and 1965 to 1990.
Nevertheless, nobody has been able to demonstrate an upward or a downward trend for the number and severity of droughts in the drylands during contemporary times. But all the scientists in Africa have observed a slipping towards the south of the isohyets corresponding to the drylands (Fig. 85).
7.2 Human Causes
Stagnation and even declining economies, mainly in the African drylands: only four countries in the Sudano-Sahelian region achieved more than 3% economic growth between 1980 and 1985; most experienced a decline (Warren and Khogali 1992). Civil wars and the associated train of disturbances: the three worst examples in 1993 are Angola, Somalia and Sudan. Bad agricultural choices: in the Sahel where drought was very severe in 1983 and 1984; in 1984 in five countries, namely Burkina Faso, Mali, Niger, Senegal, and Chad, the cotton yield beat all the records with 154 million tons (22.7 million tons in 1961-1962). But cotton is mainly produced by modest farmers and replaces food crops. The Sahel in the same year imported 1.7 million tons of cereals (200000 t/year in the early 1960s), which is also a record (Timberlake 1985). Demographic explosion common to all dry ecosystems, mainly in Asia and Africa. In the last half century, many drylands have in fact seen a rapid increase in their population at a rate of 2.5 to 3%/year, i.e., doubled at each generation.· The World Map of Soil Degradation (Oldeman et al. 1990) highlights the correlation between soil degradation and demographic excesses, particularly in the drylands of western China, in the Sahel, in the Maghreb, in the Near and Middle East, and in eastern Africa, mainly Kenya where the population growth surpasses 4%/year.
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The demographic explosion is responsible for: (1) increasing pressure on the land; (2) vegetation changes; (3) shortening of the fallow cycles and all the consequences, such as poorer soils and greater necessity of human labor for poorer results; (4) cultivation of marginal land; (5) soil degradation. Zhu Zhenda and Liu, Shu (1983) have demonstrated in the sandy steppes of Inner Mongolia that wind erosion has truncated 6 to 20 mm/year in the previously fixed sands, i.e., 200 to 300 t/halyear.
Demography means also the animal demographic explosion, with overgrazing, particularly in the drylands of Central Asia (Kazakstan, Kirghistan, Uzbekistan, Tadjikistan and Turkmenistan), of China (mainly in Sinkiang), in Latin America, in North America and less in Australia.
Uncontrolled demography has triggered overcultivation, overgrazing, overexploitation of marginal lands and shortening of fallow. Accompanied by bad management, environmental changes have appeared due to exacerbated physical and chemical mechanisms of degradation.
In the middle of 1985 the famine spread out through Africa from the Atlantic coast to the Horn of Africa and toward the south into Mozambique and the Bantustan lands of South Africa (Timberlake 1985). This situation is a temporary end of a long chain of events. The first apparent event was the drought which began at the end of the 1960s from 1968 to 1973 in the Sahel. After an interruption of a couple of years, the drought began again and culminated in 1984. The Horn of Africa, less affected than the Sahel during the first period of drought (1968-1973), was more dramatically affected in the second period of drought, mainly in 1984. Thirty-five million people experienced famine and 10 million were ecological refugees in the whole drought-affected countries of Afri-ca.
Droughts are natural disasters, but famines are not caused simply by a deficit rainfall. Bad use of the land, mismanagement, and overexploitation, which became, because of demographic explosion, a necessity in the Third World, transformed drought into a major disaster which affected an increasing number of people. In the end of the 1960s drought affected 18.5 million people per years. The number increased to 24.4 million people per year in the years 1970s, and 30 million people in Africa alone for the year 1985 (Timberlake 1985).
The couple drought-famine exists only in a context of bad management, poverty, economic disorganization, underdevelopment, and, above all, illiteracy or lack of education. The drought of 1983 in the USA and in Australia did not end in death by famine; the victims were only economic victims and precisely those who before the drought were debt afflicted. Desertification is a variable phenomenon according to the degree of development. With financial resources, technical ability, skill, an analytical approach of the natural and human problems, political balance, and a balanced ratio between land surface and population, land degradation and even desertification are not problems.
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Some Conclusions
1. Desertification is the ultimate step of land degradation: irreversibly sterile land, meaning irreversible in human terms and within practical economic limitations.
2. Where does the responsibility for land degradation lie? With human and/or natural causes? The discussions are ongoing. Man is both the creator and the victim of land degradation but drought is the revealer and the accelerator. Both man-made and natural causes are catalysts to land degradation. The proportion of each is difficult to assess.
3. The existence of desertification itself is also a debate. This debate is clarified by the distinction between land degradation, which may be considered reversible, and desertification, which should be considered as the irreversible degree ofland degradation.
4. Another differentiation could help in the approach of the concept: (a) deterioration of the land quality; and (b) biological degradation of the productivity of land. The first may be seen as caused by man; the second has been caused by climatic factors.
5. The notions of carrying capacity and of the equilibrium of dry ecosystems are not quantitatively known. The level of rehabilitation of the equilibrium in dry ecosystems between two droughts is very difficult to assess.
6. The notion of sustainable development, which was launched by the Brundtland report, is still a theoretical notion and leads to the question: What is development, when development is in opposition with environmental conservation? The notion of limits of development should be taken into account in the framework of environmental preservation.
7. With the demographic growth, in advance of the growth of agricultural production, the bad use and overuse of land in the Third World has become an obligation and has transformed drought into an economic and social disaster.
8. We are able to distinguish three facets of desertification: causes, processes, and effects. Can we fight on a reasonable time scale against the causes? Certainly not, because we know nothing about the mechanisms of drought, and also because several generations will be necessary to transform the socioeconomic structures of the affected countries. But immediate should be the battle against the physical processes and their effects of deterioration, and support for the needs as defined by the farmers and pastoralists themselves, who are the actual participants of the fight: "The front line troops in this battle against desertification are generally impoverished and illiterate, overworked peasant farmers or pastoralists and most often women. Their priority is to feed their families, now. The challenge, and the opportunity, for the Convention, is to provide real support to them, of the kind they need, so that land use becomes sustainable, not destructive" (Elisabeth Dowdeswell, Executive Director, UNEP, first session at the INCD Nairobi, May-June 1993).
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9. At the level of strategies , the advantage of a global strategy is to bring about the possibility of thinking on a megascale, but land degradation cannot be combated globally because, even if it is a megascale phenomenon, it is in fact the juxtaposition of difficulties and problems at a local scale.
In this framework of global solutions are located the immense former USSR irrigation schemes and the greenbelts, among them the Algerian, Kazaks and Chinese ones: what are the objectives of such greenbelts? To contain the desert and mainly the aeolian material- essentially dust - which is exported out of the desert. But the desert is a continuum which has no fixed limits; its boundaries are fluctuating and so unstable that it is very difficult to fix a place for the greenbelts. On the other hand, a greenbelt requires large-scale collective work, most often achieved by a totalitarian political regime, in contradiction with the individualism of the rural people.
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Fig. 8S Shifting ofthe isohyets in western Africa from 1951 to 1983 (after Carbonnei, unpublished).
