Keywords Soil erosion, soil degradation, small-scale farming, poverty, soil ... example, by a factor of 2.75 between 1950 and 1985 for grain cereals. (FAOSTAT .... FAOSTAT(2005) reports a 2.75-fold,increase for cereals between 1961 and 2003. ..... ity declined by 33%, and maize and haricot bean yields by 20-30% in' about.
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Chapter 4
Soil Erosion and Conservation in Global Agriculture Hans Hurni, Karl Herweg, Brigitte Portner,. and Hanspeter Liniger
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Abstract About one-sixthof the world's land area, that is, about one-third of the land used for agriculture,has been affectedby soil degradationin the historic past While most of this damage was caused by water and wind erosion, other forms of soil degradation are induced by biological,chemical,and physical processes.Since the 1950s, pressure on agricultura1land has increased considerablyowing to population growth and agricultural modernization. Small-scalefarming is the largest occupation in the world, involving over 2.5 billion people, over 70% of whom live below the poverty line. Soil erosion, along with other environmentalthreats, particularly affects these . farmersby diminishingyields that are primarilyused for subsistence. Soil and water conservation measures have been developed and applied on many farms. Local and science-based innovations are available for most agroecological conditions and land management and farming types. Principles and measures developed for small-scale as well as modem agricultural systems have begun to show positive impacts in most regions of the world, particularly in wealthier states and modem systems. Much more emphasis still needs to be given to small-scale farming, which requires external support for investmentin sustainable land management technologies as an indispensable and integral component of farm activities. Keywords Soil erosion, soil degradation, small-scale farming, poverty, soil conservation, water conservation, sustainable land management
4.1 Introduction 4.1.1 Background and Research Questions Global agricultural production basically consists of food for people, feed for livestock, fiber for industry, and fuel for energy. In fact, 95% of the agricultural output is produced on cultivation and grazing lands (Humi et al., 1996), the rest being the products of marine ecosystems. About 11% of the surface of the world's terrestrial
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ecosystem is used for cultivation, another 25% is used for grazing or grass-cutting, a further 28% is covered by natural and planted forests of different qualities, and about 36% is desert land (FAOSTAT,2005). The world's human population has increased by a factor of 2.49 since 1950 (Worldwatch Institute, 2005), causing demand for the above-mentioned products to grow even faster due to increased dietary as well as other per capita demands. Agricultural production, on the positive side, increased even f~ster, for example, by a factor of 2.75 between 1950 and 1985 for grain cereals (FAOSTAT,2005), and has remained at about this level. This early increase was due to a number of factors, including advances in agricultural research and technology, plant breeding, increased inputs in minerals and fertilizer, a slight expansion of cultivated land by a factor of, 1.13 (FAOSTAT, 2005), and intensification on currently cultivated land. At present, it appears that both the area of agricultural land and the productivity potentials have reached their upper limits, with little scope to (a) further expand agricultural land sustainably and (b) develop plants that are capable of producing even more per hectare without negatively affecting people and ecology. This, however, is contested by some scientists who claim that there are still vast areas of underutilized arable land, and others who believe that biotechnology will find additional possibilities to enhance plant and animal productivity. In the last 50 years, pressure on soil and water resources has been considerably accelerated in many places, along with agricultural intensification and particularly expansion. In response, there have been efforts to conserve soil and water and to find means of agricultural production that minimize negative impacts. Much of this reproductive activity, however, is being challenged by persistent poverty, while current actions to reduce poverty in many countries often put even greater strain on agnculturalland resources. Based on these statements the following five research questions were developed as guidelines for the present chapter:
1. Howhas agriculturaldevelopmentsince 1950affectedlandresources?
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2. How do these changes and prospects relate to processes of soil erosion and land degradation? 3. What is the situation of agriculture today in terms of global poverty, production of food, feed, fiber and fuel, and natural resources? 4. What are the visions for global agriculturein 2050 vis-a.-vishuman and livestock demands? 5. What potential do soil and water conservationhave to achieve sustainable land management now and in future? It seems obvious that a chapter attempting to answer the above research questions will remain largely interpretative, as only scarce. scientific evidence has been produced at the global level that could conclusively anE;werthem. There is, nevertheless, a great need to address these questions, not only in this rather superficial global assessment, but to a much greater extent through intensified scientific research.
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4 Soil Erosion and Conservation in Global Agriculture
4.1.2
Main Hypothesis and Theoretical Concepts
The main hypothesis of this chapter is that global agriculture has the potential to further increase its overall output and feed a growing world population, basically by (a) sustainably enhancing the productivity of small-scale farms and investing in their resource-conserving agricultural technologies and (b) sustainably maintaining industrialized agriculture, which should be capable of feeding growing urban populations. Research questions 1, 2, 3, and 5 will basically be addressed by synoptically reviewing statistical data and literature, and by interpreting global overviews with maps and country-level indicators. Research question 4 will follow the conceptual framework developed by the International Assessment of Agricultural Science and Technology for Development (IAASTD) as presented
in Fig. 4.1.
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The implicit theoretical foundation underlying Fig. 4.1 combines a systemic view of agriculture with a normative view of sustainable development. The conceptual framework of IAASTD (2005) in Fig. 4.1 basically looks at agricultural outputs and services, which are determined or influenced by direct and indirect drivers. Indirect drivers are frame conditions such as policies, economic factors, or science and technology, which together influence the direct drivers. The latter act as factors "on the ground" in relation to the production of agricultural goods (i.e., outputs) and services, including forestry and fishery. Direct drivers are thus natural resources, agricultural technology, energy, and
Fig. 4.1 Conceptual framework of the IAASTD. (Modified by H. Hurni)
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farm labor. All together the drivers and agricultural outputs and services are oriented toward goals, and can be influenced by these, namely development goals as pursued by individuals, households, communities, and national or international bodies, or sustainability goals now being increasingly introduced at all levels, particularly in view of the overall goal of safeguarding future demands on agriculture without compromising present demands. Sustainable development is used as a theoretical concept according to the definition by the World Commission on Environment and Development, namely to "satisfy the needs of the present without compromising the needs of future generations" (WCED, 1987). There is thus a claim to assess the intra-generational dimension looking at social, ecological, and economic sustainability, as well as the intergenerational dimension in relation to, future generations in the same dimensions.
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It is, however, necessary to enhance the conceptual framework of Fig. 4.1. This is currently being discussed in the IAASTD process, with inputs by the main author, the results of which will be published in 2008. This relates to the introduction of a further analytical level, namely typology and analysis of ecological, agricultural, and production systems, which are the basis of agricultural outputs and services and within which drivers have an impact (see Fig. 4.1). This analytical level will allow assessment of changes in the main types of agricultural systems over time, particularly in terms of their resource base, farming systems, and farm household strategies.
4.1.3
Materials and Methods
The present chapter provides a meta-analysis of select information and knowledge generated by science and science-based assessments since 1950. The analysis is illustrated with empirical evidence produced by some of the authors .
over the last 20-30 years. It attempts to look into the future (2050) using a conceptqal framework. While the chapter does not produce new scientific knowledge in a disciplinary field, it is innovative in its integrative interpretation of available scientific information.
The chapter is based on a reviewof statisticaldata and literature on agriculture, natural resources, and related frame conditions for agricultural development, such as rural livelihoods, industrialization, urbanization, and the status of human development. Country-level indicators are used to develop a global overview of disparities in development in the agricultural and other sectors. Other global overviews relate to global assessments and related maps, including a critical analysis of their methodologies. The conceptual framework developed by IAASTD (2005) is used as a guideline and critically assessed. For local case studies reference is made to results published primarily by the authors and the programs in which they work.
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4 Soil Erosion and Conservation in Global Agriculture
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