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Dryland forestry for sustainable development
Journal of Arid Environments (1995) 30:143--152
Review
Dryland forestry for sustainable development Peter F. Ffolliott*, Gerald J. Gottfriedt & W. J. Rietveld$ *School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721, U.S.A. tRocky Mountain Forest and Range Experiment Station, USDA Forest Service, Flagstaff, Arizona 86001, U.S.A. ~Rocky Mountain Forest and Range Experiment Station, USDA Forest Service, Lincoln, Nebraska 68583-0822, U.S.A. (Received 29 December 1993, accepted 19 February 1994) Dryland forestry is concerned with the management of trees and shrubs for sustainable development of dryland regions of the world. Applications of dryland forestry include the production of wood for fuel, poles and posts, and building materials; fi'uit and nut production; fodder, browse, and forage production; modification of local microclimates for improved agricultural crop production; and protection of lands susceptible to water or wind erosion, etc. These applications are combined into land-use practices linked to people's needs and social values. Dryland forestry, therefore, can be defined more broadly as the management and often establishment of trees and shrubs to improve the livelihood and quality of life for people in dryland regions.
Keywords:
aridity; forestry; forest products; sustainable development
forest implementation;
Introduction Forestry has not b e e n practised on a sustainable basis in m a n y dryland regions of the world. Exceptions can be f o u n d on some drylands of developed countries, where capital investments have b e e n sufficient to m a k e forestry economically justifiable. Even in these cases, however, applications of forestry often are 'extrapolations' f r o m forestry practices in the moist tropical and other t e m p e r a t e regions, which has led to ineffective and inefficient land m a n a g e m e n t in m a n y instances. Drylands are diverse in terms of climate, soils, vegetation and animals, and people's activities (Armitage, 1987; Child et al., 1987; F A O , 1989a). Because of this diversity, no practical characterization or definition of 'drylands' can be made. One binding feature of all drylands in the world, however, is the aridity. Aridity can be expressed in a n u m b e r of ways as a function of rainfall and temperature. One representation of 0140-1963/95/020143 + 10 $08.00/0
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aridity is the index used by the United National Educational, Scientific and Cultural Organization (UNESCO, 1977), expressed as the ratio of average annual precipitation to average potential evapotranspir'ation, the latter calculated b y Penman's method, taking into account atmospheric humidity, solar radiation, and wind (UNESCO, 1977; Baumer & Ben Salem, 1985). Three bioclimatical zones with varying degrees of aridity have been delineated by this index: hyper-arid (<0.03), arid (0.03-<0.20), and semi-arid (0.20-<0.50). Hyper-arid zones cover 4.2%, arid zones 14.6%, and semi-arid zones 12.2% of the land area of the world. Almost one-third of the total land area of the world, therefore, is considered to be characterized by aridity. These lands, together with their subhumid margins (0.50-<0.75), comprise the 'drylands' of the world, areas where deserfification is occurring at alarming rates and threatening the livelihoods of 850 million inhabitants. A distinction between the meaning of desertification and drought should be made. Desertification is a man-made disaster that is attributed to over-grazing of livestock, over-cultivation of agricultural crops, deforestation, or combinations thereof (Wickens, 1989). While desertification is due to people's abuse of the environment, drought is a natural disaster or misfortune. Drought is part of the global climatical patterns, although it is suspected that the increased albedo brought about by desertification can also adversely influence rainfall. The United Nations Environment Program (UN'EP) has estimated that 35 million km 2 of the world, an area approximately the size of both North and South America, are potentially threatened by desertification processes (FAO, 1989b). Nearly 20 million km 2 of this area have been classified as being subjected to 'high' and 'very high' desertification risks. Equally important is the fact that 30,000 km 2 are reduced to a state of 'uselessness' every year, a loss that is expected to continue unless affected countries increase their commitments to remedial actions (FAO, 1989b). Proper applications of forestry practices often can halt, and eventually reverse, the processes of desertification and other forms of land degradation on drylands. Dryland forestry, simply stated, is concerned with the management of trees and shrubs for sustainable development of dryland regions of the world. Applications of dryland forestry are broad in scope, including the production of wood for fuel, poles and posts, and building materials; fruit and nut production; fodder, browse, and forage production; modification of local microclimates for improved agricultural crop production; and protection of lands susceptible to water or wind erosion. These interventions must be based on sound technical knowledge and appreciation of human, ecological, and socio-economic factors to be effective (Falloux & Mukendi, 1987). Successful interventions also require that responsible personnel be kept abreast of technological progress in forestry-related fields. One problem, however, is a lack of appreciation of the roles of trees and shrubs in the sustainable development of drylands.
Roles of trees and shrubs
Trees and shrubs, both indigenous and introduced, play vital roles in maintaining ecological balances on drylands, improving livelihoods of local people in dryland regions (Gregersen et al., 1989), and helping to combat the devastating effects of desertification (Ben Salem, 1988; FAO, 1989b). The arrangements and functions of trees and shrubs in dry landscapes must be analysed and understood, if these roles are to be developed and expanded further.
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Arrangements of trees and shrubs in rural landscapes Pressures on drylands for agricultural crop production and animal husbandry are high, so high that lands unsuitable for agriculture frequently are used in a desperate effort to grow crops or raise livestock. As a consequence, forestry often is relegated to lands which are too poor for crop growth or livestock production. This frequent misconception that forestry is best suited for poor sites is incorrect. It must be realized that forestry, like agriculture, places demands on land to reach sustainable production levels. Two basic requirements are needed to achieve sustainable levels in forestry interventions--trees and shrubs should not be confined to areas designated as 'marginal', and forestry practices must be integrated into overall land-use strategies (FAO, 1989a). Trees and shrubs can be located in dry landscapes in numerous ways and for a variety of purposes, including: Windbreak plantings to protect agricultural crops and pastures against wind desiccation, and minimize soil erosion by wind. Interplantings with agricultural crops to protect the crops, enrich the soil, and provide wood and speciality (non-woody) products. Scattered plantings to enrich soils, provide wood, fodder and browse, and speciality products, and afford thermal protection for livestock. Linear plantations as protective buffers along roads and waterways to protect infrastructures and adjacent fields, provide shade, and contribute to the production of wood, fodder and browse, and speciality products. Greenbelt plantings around villages and urban centers for physical and psychological benefits to local inhabitants. Plantations and woodlots established under rain-fed or irrigated conditions to make the best use of often unused lands, and contribute to needed wood supplies. Managed natural forests and woodlands to maintain a stable environment and sustainable yields of essential products traditionally used by local populations. Plantings to stabilize sand dunes to protect adjacent areas from encroachment. Functions of trees and shrubs Trees and shrubs perform a number of functions on drylands. For example, they are: A source of wood products, including fuelwood, poles and posts, and timbers for building purposes. Fuelwood is almost the sole fuel for many local people, not only in rural areas but also in urbanized areas. An important source of fodder for livestock and browse for wildlife. A variety of multi-pui-pose trees and shrubs are ideal for providing high fodder yields in dry months without impairing agricultural crop production in the rainy season, while protecting and, at times, improving soil resources. A soil stabilizer and help to prevent erosion. Windbreak plantings minimize soil erosion by wind on a downwind zone that is 20 times the barrier height, and greatly reduce soil erosion by water. Trees and shrubs protect soils better and longer than annual plants. The roots of trees and shrubs deepen and improve structures of soils. Protection by trees and shrubs facilitates enrichment, such as the activities of soil organisms, decomposition, and mineralization. These functions are essential for ensuring soil stability and continuity of agricultural production. Buffer systems to protect waterways, roads, and communities. These systems intercept pollutants in runoff water, stabilize channels, provide wildlife habitats, and shelter roads and human habitats. Buffer systems, therefore, provide numerous useful functions simultaneously.
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A source of food for people. Many fruits, leaves, young shoots, and roots are valuable foods in the dry season, and comprise an important reserve for long-term subsistence and emergencies. A form of protection to enable the growing of sensitive crops like vegetables, fruits, and herbs. Windbreak plantings in irrigated systems increase agricultural crop production and the efficiency of water use, and provide habitats for beneficial organisms. A source of speciality products for local people and export. Fibers, dyes, tannins and gum, essential oils, and pharmaceuticals are only a few of the numerous non-woody products obtained. Although often referred to as 'minor forest products', these nonwoody products are vitally important to people and often constitute an important part of the total land revenue. Due to unrestricted cutting of wood, over-grazing by livestock, and agricultural cultivation on unsuitable lands, many drylands have inadequate forest and woodland cover and, as a consequence, inadequate wood, fodder, and browse resources, and protection from erosion. Attempts to develop or restore drylands for sustainable use, therefore, should include a forestry component, which can benefit local people and contribute considerably to a more balanced environment. Importantly, the forestry component should not be seen separately but must be integrated with agricultural crop production and animal husbandry to optimize land use. Within the above options, the most appropriate combinations of arrangements and functions of trees and shrubs should be selected to meet needs for wood and speciality products, agricultural crop and livestock production, and ecological stability and environmental enrichment (Child et al., 1987; Ben Salem, 1988; FAO, 1989a). A proper introduction of trees and shrubs frequently improves living conditions for people and the strength of rural economies and, in doing so, contributes to sustainable development.
Dryland forestry A consultation to review and analyse this unique and expanding role of forestry was organized by the FAO in 1985 to formulate strategies for forestry in the sustainable development of drylands. One outcome of this consultation (held in Saltillo, Cohahuila, Mexico, in 1985, as a satellite meeting to the Ninth World Forestry Congress) was a further recognition of the importance of forestry as an emerging strategy for sustainable development of dryland regions (Ben Salem, 1988; FAO, 1989b). More specifically, it was determined that enhancement of tree and shrub management in these regions, within a framework of environmentally-sound land stewardship, can help to ensure that whole ecosystems contribute effectively to the production of goods and services, and to the wider aim of food security. Dryland forestry is concerned with management of trees and shrubs for conservation and sustainable development. Applications of dryland forestry differ from applications of commercial forestry in other temperate and moist tropical ecosystems (Table 1) and, in many instances, are more broad in scope, as suggested above. Dryland forestry, therefore, can be defined more broadly as management of trees and shrubs to improve the livelihood and quality of life for people on a local scale. Dryland forestry includes many traditional forestry practices, as well as forestry practices unique to dryland environments, horticulture, livestock and wildlife management, and social science applications for analysing cultural, institutional, and economic constraints and opportunities. Special problems frequently confront people attempting to implement dryland forestry practices. Included among these problems, identified originally by the
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Table 1. Differences between dryland forestry and commercial forestry in other temperate and moist tropical ecosystems
Dryland forestry Purpose of management Management responsibility Land ownership Areas of production Mode of production Destination of products Products
Commercial forestry in other temperate and moist tropical ecosystems
Short-term, medium-term, and long-term sustained yield Mostly local people, with technical assistance Often privately owned, sometimes communal or state lands Mostly relatively small land holdings Subsistence, commercial, or mixed Often needs of local people
Medium-term and long-term sustained yield
Large variety, not only wood products hut also agricultural crops and fodder
Limited number, mostly timber and other commercial wood products
Centralized (state) organization Mostly state lands, also plantations in private sector Large tracts of land Largely commercial, occasionally subsistence Country or region
Source: adapted from Wiersum (1988)
International Union of Forestry Research Organizations (IUFRO) for consideration in Africa (IUFRO, 1987), but more generally applicable in all dryland ecosystems throughout the world, is low rainfall and its concentration in short periods during the year. Poor soils often are quite sandy and low in cation exchange and water retention capacity, or characterized by imbalances in chemical properties. High temperatures and low relative humidities generally occur. There is a lack of fast-growing indigenous tree and shrub species and, as a consequence, a dependence on exotics is common. Making a choice of tree or shrub species or proper genotype of a species for afforestation can be difficult. Plantation establishment techniques are frequently poorly developed. Little is known about improvement techniques for the few species currently used in plantations. Information on the biology and growth of plantation species is sparse. Ignorance of the silvics of important indigenous species which are adapted to local environmental conditions must be overcome. There often is inadequate knowledge of how alternative tree and shrub species would perform under these conditions. Solutions to these and other related problems are what largely separate applications of dryland forestry from forestry practices in other temperate and moist tropical regions. People also lack information on the design of forestry practices and the integration of these practices into larger-scale systems that provide multiple benefits and services. Therefore, information is needed on species combinations and compatibilities, and how to establish, manage, and protect trees and shrubs planted in the various practices. Landscape-level modeling of drylands is necessary to predict and optimize the benefits of dryland forestry to ecosystem stability and sustainability.
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Agroforestry It is important to consider agroforestry in any discussion of dryland forestry for sustainable development. Agroforestry is a collective term for land-use practices that involve the deliberate growing of woody perennials on the same piece of land as used for the production of agricultural crops and/or animals, in some form of spatial mixture or temporal in sequence, to benefit from the resultant ecological and economic interactions (MacDicken & Vergara, 1990). Agroforestry, therefore, represents varying combinations of woody, agricultural, and animal production systems. Three major types of agroforestry practices are found in the dryland regions of the world (Child et aL, 1987; Nair, 1989; MacDicken & Vergara, 1990). Agrisilvicultural practices include agricultural crop production and forestry, silvopastoral practices consist of forestry and livestock production, and agrosilvopastoral practices are combinations of agricultural crop production, forestry, and livestock production. Examples of these three and other types of agroforestry practices are shown in Table 2. There are also other agroforestry practices of importance, for example, growing of multi-purpose trees for wood, fodder and browse, and fruits. Regardless of how it is practiced, the basic aim of agroforestry is to attain ecological stability and, at the same time, provide sustainable benefits to users of the land. Agricultural crop production, livestock production, forestry, and combinations thereof are practised on the same piece of land, either simultaneously, rotationally, or spatially in agroforestry. When combinations of these land uses are implemented at the same time on the same land, agroforestry is practised simultaneously. Agroforestry practised rotationally involves alternating agricultural production, livestock production, or forestry through time on the same piece of land. Where land use practices are placed side-by-side, agroforestry is practised spatially. All three approaches are legitimate agroforestry strategies and, therefore, each should be practised where most appropriate. In many respect, agroforestry is the very essence of dryland forestry and vice versa. Both are basically small in their scale of implementation, oriented to improve the livelihood of people on a local scale, and include, in general, people-oriented forms of land use. Dryland forestry is intended to be more encompassing, however, including both the combined productions of agroforestry practices and the management of communities of woody perennials (that is, the natural forests and woodlands, and forest plantations) that occur in many dryland regions to specifically furnish fuel and other wood products, provide protection from erosion, and/or enhance amenity values.
Achieving sustainable development through dryland forestry Sustainable development is a term that is difficult to define. Furthermore, it is difficult to determine when sustainable development has been attained. There are some characteristics of the results obtained from a developmental project that generally point toward sustainability from the perspective of forestry interventions (Gregersen & Lundgren, I990). Once an intervention has met its immediate objectives and, as a consequence, is 'successful' by definition, the question of sustainability requires that characteristics of continuity, diffusion, and externalities be considered. Continuity refers to continuation of project activities and effects after the formal end of the intervention. When the activities and effects of a project stop after the intervention ends, it cannot be considered sustainable. Diffusion refers to the spread of good ideas, practices, and technologies developed by the intervention to areas outside of the project's boundaries. Most forestry interventions address only a small part of a much larger problem area, so diffusion of project concepts and practices to a
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much wider area is essential for sustainable development. Externalities refer to impacts and effects that occur outside of the project area as a result of intervention activities. For example, downstream benefits and costs that result l~om forestry practices on upstream watershed lands are externalities that must be considered in planning, implementing, and evaluating these upstream projects, because they do affect sustainability. To practise proper forestry on drylands is a challenge because a number of constraints to sustainable development of drylands must be overcome. Solutions to many of these constraints are either unknown at the present time or, if solutions are available, cannot be implemented in the absence of increased social, economic, and political commitments to their undertaking. Three commonly faced constraints affecting sustainable development are the bio-physical, the human-institutional barriers, and the low levels of investment made for implementation. Bio-physical limitations
Planning and implementation of forestry-related development projects and the achievement of sustainability normally requires that bio-physical limitations be overcome. These limitations include climate, soils, topography, and water--conditions that impose restrictions on implementation of forestry and natural resource projects. Each tree or shrub species and forest, woodland, or plantation has specific requirements for establishment, growth, and reproduction. Dryland regions impose rather harsh physical and environmental barriers to sustainable forestry. Variabilities of dryland environments require special attention when planning forestry-related interventions. Planning for forestry, livestock, or agroforestry practices must recognize and account for the uncertainties that are associated with low and erratic amounts of rainfall. Many drylands have sufficient annual precipitation to develop productive forestry systems, but the rains often fall all at once with considerable runoff, resulting in little replenishment of soil moisture. In addition, dryland regions often experience annual periods of several months with little or no rainfall. Tree and shrub species must be able to become established, grow, and, in natural systems, reproduce under conditions of limited soil moisture. The species also must be able to survive droughts that, although certain to occur, are none-the-less unpredictable. Tree and shrub species should be selected that are adapted to conditions of dryland environments and, at the same time, produce goods, services, and amenities needed by people. Human-institutional limitations
Human-institutional limitations include all of the social, economic, technological, cultural, legal, and political factors that might affect sustainability of a forestry intervention. The particular characteristics of a particular social-economic-cultural system in one part of the world can provide barriers and opportunities that are not found elsewhere. Land tenure institutions, and problems of the homeless, landless, or refugees can all affect sustainability of forest-related development. Other limitations include institutional deficiencies such as a lack of adequate knowledge or technology; human and capital resources; institutions and institutional support, including infxastructures and organizations; and incentives among different groups of people involved with or affected by forestry-related developmental projects. People cor~ont serious technical problems in attempting to introduce forestry practices onto drylands, because of an inadequate knowledge of proper forestry practices. Inadequate knowledge of forestry practices generally can be related to inadequate and incomplete technical references and extension services. In turn, it becomes difficult to educate professional foresters and local people on applications of
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forestry on drylands. This problem is being eliminated, to some extent, by educational and training problems for foresters, but it frequently remains a problem for local people. Many rural people, whose willing co-operation is imperative to sustainable development, have a tradition of agriculture which is not necessarily matched by a similar attitude towards forestry. This lack of appreciation of forestry can be a barrier to initiation of sustainable forestry practices, especially on marginal agricultural lands. This barrier can be alleviated by providing guidance through the education and training of people, extension services, and, most of all, by demonstrating the beneficial effects of trees and shrubs in demonstration plots established on a farmer's land. Methods of overcoming the human-institutional and bio-physical limitations to all forms of sustainable development of drylands include changing and improving institutions, developing and disseminating appropriate technologies, and providing education, training, and extension. However, investment, employment, and income generation also are required for these barriers to be overcome.
Low levels of investment Dryland regions of the world, in general, suffer from a vicious cycle of low productivity, low levels of investment, and, as a result, poverty. Investments, apart from those made for irrigated agricultural production, are relatively low. To illustrate this point, in The World Bank assistance-projects in eastern and southern Africa in the middle 1980s, interventions in areas that received less than 900 mm of annual rainfall were only 15% of a total of $374 million in loans (Marples, 1986, p.87). Private investments by farmers in rain-fed agriculture also is minimal in dryland regions, largely because of the higher uncertainties of receiving sufficient rainfall. This lack of investment has exacerbated the gap in agricultural-related productivity (of which forestry is often an integral component) between rain-fed drylands and irrigated or wetter rain-fed areas. Low productivity, low levels of investment, and land degradation in rain-fed areas are responsible for regional poverty and income disparities. Poverty and hunger that is prevalent in sub-Saharan Africa is, perhaps, the most poignant example. However, critical conditions also are found elsewhere. Improving this situation requires that a variety of technical and institutional problems be solved, chief among them being the need to increase levels of investment in appropriate agricultural, forestry, and agroforestry interventions. Others are to design strategies for risk management and implement programs for equitable land distribution and income.
Summary Hyper-arid, arid, and semi-arrd zones, and their sub-humid margins, cover approximately 30% of the earth's land surface and are inhabited by about 850 million people. Desertification is accelerating and becoming critical in these regions. Interventions through proper use of forestry practices can halt or reverse this trend in many instances. Trees and shrubs can provide a variety of wood products, and, at the same time, protection of agricultural crops, livestock, and people from an often harsh environment. For forestry interventions to be successful, however, people must begin to appreciate the important roles that trees and shrubs can play for their economic welfare and the rehabilitation of degraded lands. Foresters, extension workers, political leaders, and the general population must realize that dryland forestry practices are different from those found in more temperate and moist tropical regions. The ecology of the indigenous or introduced species of trees and shrubs may not be adapted to traditional
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methods. T h e dry climate confronted also presents unique challenges. T h e management of wooded drylands is constrained, in many situations, by different ownership patterns, production goals, and managerial strategies. Bio-physical limitations, human-institutional limitations, and low levels of investment constrain successful forestry interventions. One important goal of dryland forestry interventions is to achieve sustainability. A developmental project, regardless of its purposes, should have continuity after the formal end of the intervention and, ideally, an impact outside of the immediate project area. External forces such as climate and human-institutional barriers also affect the success of a project. These barriers can be overcome by changing institutions, improving economic opportunities, developing and disseminating appropriate technologies, and providing education, training, and extension services.
References Anonymous. (1983). A global inventory of agroforestry systems. Biomass, 3: 241-245. Armitage, F.B. (1987). Irrigated Forestry in Arid and Semi-arid Lands: A synthesis. International Development Research Centre, Ottawa, Canada. 160 pp. Baumer, M.N. & Ben Salem, B. (1985). The arid zone, In: FAO. Sand dune stabilization, shelterbelts and afforestation. Conservation Guide 10, Food and Agriculture Organization of the United Nations, Rome, pp. 1-8. Ben Salem, B. (1988). A strategy on the role of forestry in combating desertification. In: Whitehead, E.E., Hutchinson, C.F., Timmermann, B.N., & Varady, R.G. (Eds), Arid lands: Today and tomorrozo, pp. 841-869. Boulder, Colorado: West,dew Press. 1435 pp. Child, R.D., Heady, H.F., Petersen, R.A., Pieper, R.D. & Poulton, C.E. (1987). Arid and Semiarid Rangelands: Guidelines for development. Winrock International, Morrilton, Arkansas. 291 pp. Falloux, F. & Mukendi, A. (1987). Desertification control and renewable resource management in the Sahelian and Sudanian zones of West Africa. Technical Paper 70. The World Bank, Washington, DC. 119 pp. FAO. (1989a). Arid zone forestry: a guide for field technicians. Conservation Guide 20, Food and Agriculture Organization of the United Nations, Rome. 143 pp. FAO. (1989a). The role of forestry in combating desertification. Conservation Guide 21, Food and Agriculture Organization of the United Nations, Rome. 333 pp. Gregersen, H.M. & Lundgren, A.L. (1990). Forestry for sustainable developments: concepts and a framework for action. Working Paper 1, Forestry for Sustainable Development (FFSD) Program, University of Minnesota, St. Paul, Minnesota. 19 pp. C_vregersen,H., Draper, S. & Elz, D. (Eds). (1989). People and Trees: The role ofsocialforestry in sustainable development. The World Bank, Washington, DC. 273 pp. International Union of Forestry Research Organizations. (1987). Africa--problems and opportunities. IUFRO Newsletter 57, Nairobi, Kenya. 20 pp. MacDicken, K.G. & Vergara, N.T. (Eds). (1990). Agroforesrry: Classification and management. New York: John Wiley & Sons, Inc. 382 pp. Marples, S. (1986). Production and investment in marginal areas. In: Davis, T.J. (Ed), Development of Rainfed Agriculture under Arid and Semiarid Conditions, p.87. Washington, DC: The World Bank. Nair, P.K.R. (Ed.) (1989). Agroforestr2 Systems in the Tropics. Boston: Kluwer Publishers. 664 PP. UNESCO (1977). Map of the world distribution of arid regions. M A B Technical Notes 7. United Nations Educational, Scientific and Cultural Organization, Paris. 54 pp. Wickens, G.E. (1989). The Sahel--a double disaster. Disaster Management, 2: 100-101. Wiersum, K.F. (1988). Outline of the agroforestry concept. In: Wiersum, K. F. (Ed.), Viewpoints on Agroforestry. Agricultural University of Wageningen, The Netherlands, pp. 1-26.
Review
Dryland forestry for sustainable development Peter F. Ffolliott*, Gerald J. Gottfriedt & W. J. Rietveld$ *School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721, U.S.A. tRocky Mountain Forest and Range Experiment Station, USDA Forest Service, Flagstaff, Arizona 86001, U.S.A. ~Rocky Mountain Forest and Range Experiment Station, USDA Forest Service, Lincoln, Nebraska 68583-0822, U.S.A. (Received 29 December 1993, accepted 19 February 1994) Dryland forestry is concerned with the management of trees and shrubs for sustainable development of dryland regions of the world. Applications of dryland forestry include the production of wood for fuel, poles and posts, and building materials; fi'uit and nut production; fodder, browse, and forage production; modification of local microclimates for improved agricultural crop production; and protection of lands susceptible to water or wind erosion, etc. These applications are combined into land-use practices linked to people's needs and social values. Dryland forestry, therefore, can be defined more broadly as the management and often establishment of trees and shrubs to improve the livelihood and quality of life for people in dryland regions.
Keywords:
aridity; forestry; forest products; sustainable development
forest implementation;
Introduction Forestry has not b e e n practised on a sustainable basis in m a n y dryland regions of the world. Exceptions can be f o u n d on some drylands of developed countries, where capital investments have b e e n sufficient to m a k e forestry economically justifiable. Even in these cases, however, applications of forestry often are 'extrapolations' f r o m forestry practices in the moist tropical and other t e m p e r a t e regions, which has led to ineffective and inefficient land m a n a g e m e n t in m a n y instances. Drylands are diverse in terms of climate, soils, vegetation and animals, and people's activities (Armitage, 1987; Child et al., 1987; F A O , 1989a). Because of this diversity, no practical characterization or definition of 'drylands' can be made. One binding feature of all drylands in the world, however, is the aridity. Aridity can be expressed in a n u m b e r of ways as a function of rainfall and temperature. One representation of 0140-1963/95/020143 + 10 $08.00/0
© 1995 Academic Press Limited
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aridity is the index used by the United National Educational, Scientific and Cultural Organization (UNESCO, 1977), expressed as the ratio of average annual precipitation to average potential evapotranspir'ation, the latter calculated b y Penman's method, taking into account atmospheric humidity, solar radiation, and wind (UNESCO, 1977; Baumer & Ben Salem, 1985). Three bioclimatical zones with varying degrees of aridity have been delineated by this index: hyper-arid (<0.03), arid (0.03-<0.20), and semi-arid (0.20-<0.50). Hyper-arid zones cover 4.2%, arid zones 14.6%, and semi-arid zones 12.2% of the land area of the world. Almost one-third of the total land area of the world, therefore, is considered to be characterized by aridity. These lands, together with their subhumid margins (0.50-<0.75), comprise the 'drylands' of the world, areas where deserfification is occurring at alarming rates and threatening the livelihoods of 850 million inhabitants. A distinction between the meaning of desertification and drought should be made. Desertification is a man-made disaster that is attributed to over-grazing of livestock, over-cultivation of agricultural crops, deforestation, or combinations thereof (Wickens, 1989). While desertification is due to people's abuse of the environment, drought is a natural disaster or misfortune. Drought is part of the global climatical patterns, although it is suspected that the increased albedo brought about by desertification can also adversely influence rainfall. The United Nations Environment Program (UN'EP) has estimated that 35 million km 2 of the world, an area approximately the size of both North and South America, are potentially threatened by desertification processes (FAO, 1989b). Nearly 20 million km 2 of this area have been classified as being subjected to 'high' and 'very high' desertification risks. Equally important is the fact that 30,000 km 2 are reduced to a state of 'uselessness' every year, a loss that is expected to continue unless affected countries increase their commitments to remedial actions (FAO, 1989b). Proper applications of forestry practices often can halt, and eventually reverse, the processes of desertification and other forms of land degradation on drylands. Dryland forestry, simply stated, is concerned with the management of trees and shrubs for sustainable development of dryland regions of the world. Applications of dryland forestry are broad in scope, including the production of wood for fuel, poles and posts, and building materials; fruit and nut production; fodder, browse, and forage production; modification of local microclimates for improved agricultural crop production; and protection of lands susceptible to water or wind erosion. These interventions must be based on sound technical knowledge and appreciation of human, ecological, and socio-economic factors to be effective (Falloux & Mukendi, 1987). Successful interventions also require that responsible personnel be kept abreast of technological progress in forestry-related fields. One problem, however, is a lack of appreciation of the roles of trees and shrubs in the sustainable development of drylands.
Roles of trees and shrubs
Trees and shrubs, both indigenous and introduced, play vital roles in maintaining ecological balances on drylands, improving livelihoods of local people in dryland regions (Gregersen et al., 1989), and helping to combat the devastating effects of desertification (Ben Salem, 1988; FAO, 1989b). The arrangements and functions of trees and shrubs in dry landscapes must be analysed and understood, if these roles are to be developed and expanded further.
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Arrangements of trees and shrubs in rural landscapes Pressures on drylands for agricultural crop production and animal husbandry are high, so high that lands unsuitable for agriculture frequently are used in a desperate effort to grow crops or raise livestock. As a consequence, forestry often is relegated to lands which are too poor for crop growth or livestock production. This frequent misconception that forestry is best suited for poor sites is incorrect. It must be realized that forestry, like agriculture, places demands on land to reach sustainable production levels. Two basic requirements are needed to achieve sustainable levels in forestry interventions--trees and shrubs should not be confined to areas designated as 'marginal', and forestry practices must be integrated into overall land-use strategies (FAO, 1989a). Trees and shrubs can be located in dry landscapes in numerous ways and for a variety of purposes, including: Windbreak plantings to protect agricultural crops and pastures against wind desiccation, and minimize soil erosion by wind. Interplantings with agricultural crops to protect the crops, enrich the soil, and provide wood and speciality (non-woody) products. Scattered plantings to enrich soils, provide wood, fodder and browse, and speciality products, and afford thermal protection for livestock. Linear plantations as protective buffers along roads and waterways to protect infrastructures and adjacent fields, provide shade, and contribute to the production of wood, fodder and browse, and speciality products. Greenbelt plantings around villages and urban centers for physical and psychological benefits to local inhabitants. Plantations and woodlots established under rain-fed or irrigated conditions to make the best use of often unused lands, and contribute to needed wood supplies. Managed natural forests and woodlands to maintain a stable environment and sustainable yields of essential products traditionally used by local populations. Plantings to stabilize sand dunes to protect adjacent areas from encroachment. Functions of trees and shrubs Trees and shrubs perform a number of functions on drylands. For example, they are: A source of wood products, including fuelwood, poles and posts, and timbers for building purposes. Fuelwood is almost the sole fuel for many local people, not only in rural areas but also in urbanized areas. An important source of fodder for livestock and browse for wildlife. A variety of multi-pui-pose trees and shrubs are ideal for providing high fodder yields in dry months without impairing agricultural crop production in the rainy season, while protecting and, at times, improving soil resources. A soil stabilizer and help to prevent erosion. Windbreak plantings minimize soil erosion by wind on a downwind zone that is 20 times the barrier height, and greatly reduce soil erosion by water. Trees and shrubs protect soils better and longer than annual plants. The roots of trees and shrubs deepen and improve structures of soils. Protection by trees and shrubs facilitates enrichment, such as the activities of soil organisms, decomposition, and mineralization. These functions are essential for ensuring soil stability and continuity of agricultural production. Buffer systems to protect waterways, roads, and communities. These systems intercept pollutants in runoff water, stabilize channels, provide wildlife habitats, and shelter roads and human habitats. Buffer systems, therefore, provide numerous useful functions simultaneously.
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A source of food for people. Many fruits, leaves, young shoots, and roots are valuable foods in the dry season, and comprise an important reserve for long-term subsistence and emergencies. A form of protection to enable the growing of sensitive crops like vegetables, fruits, and herbs. Windbreak plantings in irrigated systems increase agricultural crop production and the efficiency of water use, and provide habitats for beneficial organisms. A source of speciality products for local people and export. Fibers, dyes, tannins and gum, essential oils, and pharmaceuticals are only a few of the numerous non-woody products obtained. Although often referred to as 'minor forest products', these nonwoody products are vitally important to people and often constitute an important part of the total land revenue. Due to unrestricted cutting of wood, over-grazing by livestock, and agricultural cultivation on unsuitable lands, many drylands have inadequate forest and woodland cover and, as a consequence, inadequate wood, fodder, and browse resources, and protection from erosion. Attempts to develop or restore drylands for sustainable use, therefore, should include a forestry component, which can benefit local people and contribute considerably to a more balanced environment. Importantly, the forestry component should not be seen separately but must be integrated with agricultural crop production and animal husbandry to optimize land use. Within the above options, the most appropriate combinations of arrangements and functions of trees and shrubs should be selected to meet needs for wood and speciality products, agricultural crop and livestock production, and ecological stability and environmental enrichment (Child et al., 1987; Ben Salem, 1988; FAO, 1989a). A proper introduction of trees and shrubs frequently improves living conditions for people and the strength of rural economies and, in doing so, contributes to sustainable development.
Dryland forestry A consultation to review and analyse this unique and expanding role of forestry was organized by the FAO in 1985 to formulate strategies for forestry in the sustainable development of drylands. One outcome of this consultation (held in Saltillo, Cohahuila, Mexico, in 1985, as a satellite meeting to the Ninth World Forestry Congress) was a further recognition of the importance of forestry as an emerging strategy for sustainable development of dryland regions (Ben Salem, 1988; FAO, 1989b). More specifically, it was determined that enhancement of tree and shrub management in these regions, within a framework of environmentally-sound land stewardship, can help to ensure that whole ecosystems contribute effectively to the production of goods and services, and to the wider aim of food security. Dryland forestry is concerned with management of trees and shrubs for conservation and sustainable development. Applications of dryland forestry differ from applications of commercial forestry in other temperate and moist tropical ecosystems (Table 1) and, in many instances, are more broad in scope, as suggested above. Dryland forestry, therefore, can be defined more broadly as management of trees and shrubs to improve the livelihood and quality of life for people on a local scale. Dryland forestry includes many traditional forestry practices, as well as forestry practices unique to dryland environments, horticulture, livestock and wildlife management, and social science applications for analysing cultural, institutional, and economic constraints and opportunities. Special problems frequently confront people attempting to implement dryland forestry practices. Included among these problems, identified originally by the
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Table 1. Differences between dryland forestry and commercial forestry in other temperate and moist tropical ecosystems
Dryland forestry Purpose of management Management responsibility Land ownership Areas of production Mode of production Destination of products Products
Commercial forestry in other temperate and moist tropical ecosystems
Short-term, medium-term, and long-term sustained yield Mostly local people, with technical assistance Often privately owned, sometimes communal or state lands Mostly relatively small land holdings Subsistence, commercial, or mixed Often needs of local people
Medium-term and long-term sustained yield
Large variety, not only wood products hut also agricultural crops and fodder
Limited number, mostly timber and other commercial wood products
Centralized (state) organization Mostly state lands, also plantations in private sector Large tracts of land Largely commercial, occasionally subsistence Country or region
Source: adapted from Wiersum (1988)
International Union of Forestry Research Organizations (IUFRO) for consideration in Africa (IUFRO, 1987), but more generally applicable in all dryland ecosystems throughout the world, is low rainfall and its concentration in short periods during the year. Poor soils often are quite sandy and low in cation exchange and water retention capacity, or characterized by imbalances in chemical properties. High temperatures and low relative humidities generally occur. There is a lack of fast-growing indigenous tree and shrub species and, as a consequence, a dependence on exotics is common. Making a choice of tree or shrub species or proper genotype of a species for afforestation can be difficult. Plantation establishment techniques are frequently poorly developed. Little is known about improvement techniques for the few species currently used in plantations. Information on the biology and growth of plantation species is sparse. Ignorance of the silvics of important indigenous species which are adapted to local environmental conditions must be overcome. There often is inadequate knowledge of how alternative tree and shrub species would perform under these conditions. Solutions to these and other related problems are what largely separate applications of dryland forestry from forestry practices in other temperate and moist tropical regions. People also lack information on the design of forestry practices and the integration of these practices into larger-scale systems that provide multiple benefits and services. Therefore, information is needed on species combinations and compatibilities, and how to establish, manage, and protect trees and shrubs planted in the various practices. Landscape-level modeling of drylands is necessary to predict and optimize the benefits of dryland forestry to ecosystem stability and sustainability.
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Agroforestry It is important to consider agroforestry in any discussion of dryland forestry for sustainable development. Agroforestry is a collective term for land-use practices that involve the deliberate growing of woody perennials on the same piece of land as used for the production of agricultural crops and/or animals, in some form of spatial mixture or temporal in sequence, to benefit from the resultant ecological and economic interactions (MacDicken & Vergara, 1990). Agroforestry, therefore, represents varying combinations of woody, agricultural, and animal production systems. Three major types of agroforestry practices are found in the dryland regions of the world (Child et aL, 1987; Nair, 1989; MacDicken & Vergara, 1990). Agrisilvicultural practices include agricultural crop production and forestry, silvopastoral practices consist of forestry and livestock production, and agrosilvopastoral practices are combinations of agricultural crop production, forestry, and livestock production. Examples of these three and other types of agroforestry practices are shown in Table 2. There are also other agroforestry practices of importance, for example, growing of multi-purpose trees for wood, fodder and browse, and fruits. Regardless of how it is practiced, the basic aim of agroforestry is to attain ecological stability and, at the same time, provide sustainable benefits to users of the land. Agricultural crop production, livestock production, forestry, and combinations thereof are practised on the same piece of land, either simultaneously, rotationally, or spatially in agroforestry. When combinations of these land uses are implemented at the same time on the same land, agroforestry is practised simultaneously. Agroforestry practised rotationally involves alternating agricultural production, livestock production, or forestry through time on the same piece of land. Where land use practices are placed side-by-side, agroforestry is practised spatially. All three approaches are legitimate agroforestry strategies and, therefore, each should be practised where most appropriate. In many respect, agroforestry is the very essence of dryland forestry and vice versa. Both are basically small in their scale of implementation, oriented to improve the livelihood of people on a local scale, and include, in general, people-oriented forms of land use. Dryland forestry is intended to be more encompassing, however, including both the combined productions of agroforestry practices and the management of communities of woody perennials (that is, the natural forests and woodlands, and forest plantations) that occur in many dryland regions to specifically furnish fuel and other wood products, provide protection from erosion, and/or enhance amenity values.
Achieving sustainable development through dryland forestry Sustainable development is a term that is difficult to define. Furthermore, it is difficult to determine when sustainable development has been attained. There are some characteristics of the results obtained from a developmental project that generally point toward sustainability from the perspective of forestry interventions (Gregersen & Lundgren, I990). Once an intervention has met its immediate objectives and, as a consequence, is 'successful' by definition, the question of sustainability requires that characteristics of continuity, diffusion, and externalities be considered. Continuity refers to continuation of project activities and effects after the formal end of the intervention. When the activities and effects of a project stop after the intervention ends, it cannot be considered sustainable. Diffusion refers to the spread of good ideas, practices, and technologies developed by the intervention to areas outside of the project's boundaries. Most forestry interventions address only a small part of a much larger problem area, so diffusion of project concepts and practices to a
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much wider area is essential for sustainable development. Externalities refer to impacts and effects that occur outside of the project area as a result of intervention activities. For example, downstream benefits and costs that result l~om forestry practices on upstream watershed lands are externalities that must be considered in planning, implementing, and evaluating these upstream projects, because they do affect sustainability. To practise proper forestry on drylands is a challenge because a number of constraints to sustainable development of drylands must be overcome. Solutions to many of these constraints are either unknown at the present time or, if solutions are available, cannot be implemented in the absence of increased social, economic, and political commitments to their undertaking. Three commonly faced constraints affecting sustainable development are the bio-physical, the human-institutional barriers, and the low levels of investment made for implementation. Bio-physical limitations
Planning and implementation of forestry-related development projects and the achievement of sustainability normally requires that bio-physical limitations be overcome. These limitations include climate, soils, topography, and water--conditions that impose restrictions on implementation of forestry and natural resource projects. Each tree or shrub species and forest, woodland, or plantation has specific requirements for establishment, growth, and reproduction. Dryland regions impose rather harsh physical and environmental barriers to sustainable forestry. Variabilities of dryland environments require special attention when planning forestry-related interventions. Planning for forestry, livestock, or agroforestry practices must recognize and account for the uncertainties that are associated with low and erratic amounts of rainfall. Many drylands have sufficient annual precipitation to develop productive forestry systems, but the rains often fall all at once with considerable runoff, resulting in little replenishment of soil moisture. In addition, dryland regions often experience annual periods of several months with little or no rainfall. Tree and shrub species must be able to become established, grow, and, in natural systems, reproduce under conditions of limited soil moisture. The species also must be able to survive droughts that, although certain to occur, are none-the-less unpredictable. Tree and shrub species should be selected that are adapted to conditions of dryland environments and, at the same time, produce goods, services, and amenities needed by people. Human-institutional limitations
Human-institutional limitations include all of the social, economic, technological, cultural, legal, and political factors that might affect sustainability of a forestry intervention. The particular characteristics of a particular social-economic-cultural system in one part of the world can provide barriers and opportunities that are not found elsewhere. Land tenure institutions, and problems of the homeless, landless, or refugees can all affect sustainability of forest-related development. Other limitations include institutional deficiencies such as a lack of adequate knowledge or technology; human and capital resources; institutions and institutional support, including infxastructures and organizations; and incentives among different groups of people involved with or affected by forestry-related developmental projects. People cor~ont serious technical problems in attempting to introduce forestry practices onto drylands, because of an inadequate knowledge of proper forestry practices. Inadequate knowledge of forestry practices generally can be related to inadequate and incomplete technical references and extension services. In turn, it becomes difficult to educate professional foresters and local people on applications of
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forestry on drylands. This problem is being eliminated, to some extent, by educational and training problems for foresters, but it frequently remains a problem for local people. Many rural people, whose willing co-operation is imperative to sustainable development, have a tradition of agriculture which is not necessarily matched by a similar attitude towards forestry. This lack of appreciation of forestry can be a barrier to initiation of sustainable forestry practices, especially on marginal agricultural lands. This barrier can be alleviated by providing guidance through the education and training of people, extension services, and, most of all, by demonstrating the beneficial effects of trees and shrubs in demonstration plots established on a farmer's land. Methods of overcoming the human-institutional and bio-physical limitations to all forms of sustainable development of drylands include changing and improving institutions, developing and disseminating appropriate technologies, and providing education, training, and extension. However, investment, employment, and income generation also are required for these barriers to be overcome.
Low levels of investment Dryland regions of the world, in general, suffer from a vicious cycle of low productivity, low levels of investment, and, as a result, poverty. Investments, apart from those made for irrigated agricultural production, are relatively low. To illustrate this point, in The World Bank assistance-projects in eastern and southern Africa in the middle 1980s, interventions in areas that received less than 900 mm of annual rainfall were only 15% of a total of $374 million in loans (Marples, 1986, p.87). Private investments by farmers in rain-fed agriculture also is minimal in dryland regions, largely because of the higher uncertainties of receiving sufficient rainfall. This lack of investment has exacerbated the gap in agricultural-related productivity (of which forestry is often an integral component) between rain-fed drylands and irrigated or wetter rain-fed areas. Low productivity, low levels of investment, and land degradation in rain-fed areas are responsible for regional poverty and income disparities. Poverty and hunger that is prevalent in sub-Saharan Africa is, perhaps, the most poignant example. However, critical conditions also are found elsewhere. Improving this situation requires that a variety of technical and institutional problems be solved, chief among them being the need to increase levels of investment in appropriate agricultural, forestry, and agroforestry interventions. Others are to design strategies for risk management and implement programs for equitable land distribution and income.
Summary Hyper-arid, arid, and semi-arrd zones, and their sub-humid margins, cover approximately 30% of the earth's land surface and are inhabited by about 850 million people. Desertification is accelerating and becoming critical in these regions. Interventions through proper use of forestry practices can halt or reverse this trend in many instances. Trees and shrubs can provide a variety of wood products, and, at the same time, protection of agricultural crops, livestock, and people from an often harsh environment. For forestry interventions to be successful, however, people must begin to appreciate the important roles that trees and shrubs can play for their economic welfare and the rehabilitation of degraded lands. Foresters, extension workers, political leaders, and the general population must realize that dryland forestry practices are different from those found in more temperate and moist tropical regions. The ecology of the indigenous or introduced species of trees and shrubs may not be adapted to traditional
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methods. T h e dry climate confronted also presents unique challenges. T h e management of wooded drylands is constrained, in many situations, by different ownership patterns, production goals, and managerial strategies. Bio-physical limitations, human-institutional limitations, and low levels of investment constrain successful forestry interventions. One important goal of dryland forestry interventions is to achieve sustainability. A developmental project, regardless of its purposes, should have continuity after the formal end of the intervention and, ideally, an impact outside of the immediate project area. External forces such as climate and human-institutional barriers also affect the success of a project. These barriers can be overcome by changing institutions, improving economic opportunities, developing and disseminating appropriate technologies, and providing education, training, and extension services.
References Anonymous. (1983). A global inventory of agroforestry systems. Biomass, 3: 241-245. Armitage, F.B. (1987). Irrigated Forestry in Arid and Semi-arid Lands: A synthesis. International Development Research Centre, Ottawa, Canada. 160 pp. Baumer, M.N. & Ben Salem, B. (1985). The arid zone, In: FAO. Sand dune stabilization, shelterbelts and afforestation. Conservation Guide 10, Food and Agriculture Organization of the United Nations, Rome, pp. 1-8. Ben Salem, B. (1988). A strategy on the role of forestry in combating desertification. In: Whitehead, E.E., Hutchinson, C.F., Timmermann, B.N., & Varady, R.G. (Eds), Arid lands: Today and tomorrozo, pp. 841-869. Boulder, Colorado: West,dew Press. 1435 pp. Child, R.D., Heady, H.F., Petersen, R.A., Pieper, R.D. & Poulton, C.E. (1987). Arid and Semiarid Rangelands: Guidelines for development. Winrock International, Morrilton, Arkansas. 291 pp. Falloux, F. & Mukendi, A. (1987). Desertification control and renewable resource management in the Sahelian and Sudanian zones of West Africa. Technical Paper 70. The World Bank, Washington, DC. 119 pp. FAO. (1989a). Arid zone forestry: a guide for field technicians. Conservation Guide 20, Food and Agriculture Organization of the United Nations, Rome. 143 pp. FAO. (1989a). The role of forestry in combating desertification. Conservation Guide 21, Food and Agriculture Organization of the United Nations, Rome. 333 pp. Gregersen, H.M. & Lundgren, A.L. (1990). Forestry for sustainable developments: concepts and a framework for action. Working Paper 1, Forestry for Sustainable Development (FFSD) Program, University of Minnesota, St. Paul, Minnesota. 19 pp. C_vregersen,H., Draper, S. & Elz, D. (Eds). (1989). People and Trees: The role ofsocialforestry in sustainable development. The World Bank, Washington, DC. 273 pp. International Union of Forestry Research Organizations. (1987). Africa--problems and opportunities. IUFRO Newsletter 57, Nairobi, Kenya. 20 pp. MacDicken, K.G. & Vergara, N.T. (Eds). (1990). Agroforesrry: Classification and management. New York: John Wiley & Sons, Inc. 382 pp. Marples, S. (1986). Production and investment in marginal areas. In: Davis, T.J. (Ed), Development of Rainfed Agriculture under Arid and Semiarid Conditions, p.87. Washington, DC: The World Bank. Nair, P.K.R. (Ed.) (1989). Agroforestr2 Systems in the Tropics. Boston: Kluwer Publishers. 664 PP. UNESCO (1977). Map of the world distribution of arid regions. M A B Technical Notes 7. United Nations Educational, Scientific and Cultural Organization, Paris. 54 pp. Wickens, G.E. (1989). The Sahel--a double disaster. Disaster Management, 2: 100-101. Wiersum, K.F. (1988). Outline of the agroforestry concept. In: Wiersum, K. F. (Ed.), Viewpoints on Agroforestry. Agricultural University of Wageningen, The Netherlands, pp. 1-26.