The Economics of Desertification, Land Degradation, and Drought

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Figure 2.1—GLASOD (1991) global assessment of the status of human-induced soil degradation Source: Oldeman, Hakkeling, and Sombroek 1991a. Sonneveld and Dent (2009) assessed the accuracy of the GLASOD results, using some case studies in Africa. The study concluded that the GLASOD assessments were only moderately consistent with the actual data used to verify it. The analysis of the relationship between agricultural productivity and the severity of soil degradation also showed a positive relationship between maize yield and the degradation index drawn from GLASOD, which was due to the use of fertilizer, improved seeds, and other yield-enhancing practices, excluding prevention of soil erosion. This counterintuitive pattern shows the complex relationship between degradation and agricultural productivity. The GLASOD study also focused on soil degradation largely related to soil erosion; only little is said about other forms of land degradation—namely, loss of vegetation (for example, deforestation) and biodiversity. As the GLASOD study was based on expert opinion, it is prone to subjective judgment that is not easy to reproduce. GLASOD focused only on the extent and severity of soil degradation, with no assessment of efforts to prevent degradation or to rehabilitate the results of soil degradation. The study also did not identify the causes of soil degradation and its costs. Due to these and other weaknesses, most of which the authors of the study identified, follow-up studies have been commissioned and are reviewed below. In 1990, the first edition of the World Atlas of Desertification (WAD) by UNEP used the findings and products of the GLASOD approach for its atlas. The first edition was published in 1992, with the intention of depicting the status of desertification and land degradation. The second edition was published in 1997. In addition to the depiction of desertification, it contained methods to combat desertification, as well as responses to related issues, such as biodiversity, climate change, and the impact of socioeconomic determinants, such as population density (UNEP 1997b). Moreover, case studies in Africa and Asia were presented, which were based on the Assessment of Soil Degradation in Asia and Southeast Asia (ASSOD), the more regional approach of GLASOD. Though based on soil degradation data provided by GLASOD, WAD claims to depict desertification instead. This underlines the need for common definitions of the terminology used. World Overview of Conservation Approaches and Technologies The World Overview of Conservation Approaches and Technologies (WOCAT) was the first global assessment of the prevention of land degradation mitigation. The WOCAT approach shows the wealth of local knowledge regarding soil and water conservation practices used by land users in different countries around the world. WOCAT started in 1992, with the intention of pointing out achievements that had been made to combat soil degradation (Schwilch, Liniger, and Van Lynden 2004). WOCAT 14 .
was started in reaction to the GLASOD approach, in order to develop “a set tools to document, monitor, and evaluate” soil and water conservation (SWC) “know-how, to disseminate it around the globe, and to facilitate the exchange of experience” (Schwilch, Liniger, and Van Lynden 2004: 1). It was aimed at facilitating local and international exchange of knowledge by establishing the WOCAT network. A global map of SWC measures is still under construction. WOCAT also collected data on the costs of land management practices, which could allow a determination of the costs of taking action to prevent or mitigate land degradation. WOCAT conducted 42 case studies in 23 countries from six continents. However, the choice of the case study countries was not done in such a way that could allow extrapolation of the results to the rest of the world. Global Desertification Tension Zones The U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) developed global maps on global desertification tension zones, which depict areas vulnerable to desertification, wind and water erosion by natural preconditions, and human impact (Eswaran, Lal, and Reich 2001). Desertification tension zones were described with two systems: zones under low-input agricultural systems, where the “productive capacity of the land is stressed by mismanagement, generally by resource poor farmers,” and high-input agricultural systems, where tension zones “arise due to excessive use of agrochemicals, uncontrolled use of irrigation, and monoclonal plantations with minimal genetic diversity” (Eswaran, Reich, and Beinroth 1998: 1). Four degrees of severity (low, moderate, high, and very high), reminiscent to the GLASOD approach, show the degree of an area’s vulnerability to desertification or land degradation (Figure 2.2). According to the definition of desertification from UNEP, only arid, semiarid, and subhumid areas were integrated in this approach, excluding subhumid and humid, except for water erosion, which also affects humid areas. Figure 2.2—Desertification vulnerability Source: USDA-NRCS 1998. The purpose of the NRCS study was to identify and locate “desertification tension zones […] where the potential decline in land quality is so severe as to trigger a whole range of negative socioeconomic conditions that could threaten political stability, sustainability, and the general quality of life” (Eswaran, Reich, and Beinroth 1998: 1). The approach of NRCS used several data input, such as the FAO/UNESCO Soil Map of the World (1:5,000,000) and a pedoclimate map that was compiled by a climate database from records for about 25,000 stations globally, using soil moisture and temperature regimes that were superimposed on the soil map via GIS. The map of vulnerability to desertification was superimposed with an interpolated population density map from the Center for 15
Page 1 and 2: IFPRI Discussion Paper 01086 May 20
Page 3 and 4: Contents Abstract vii Acknowledgmen
Page 5 and 6: List of Figures 1.1—Conceptual fr
Page 7 and 8: ABSTRACT Attention to land degradat
Page 9 and 10: ABBREVIATIONS AND ACRONYMS ADB Asia
Page 11: SCAR Soil Conservation in Agricultu
Page 14 and 15: In the present report, the conceptu
Page 16 and 17: Framework: Confronting Action versu
Page 18 and 19: understand these arrangements in or
Page 20 and 21: Figure 1.3—Prevention, mitigation
Page 22 and 23: on assessments at the micro level (
Page 24 and 25: does not clearly distinguish betwee
Page 28 and 29: International Earth Science Informa
Page 30 and 31: Box 2.1—Continued Normalized Diff
Page 32 and 33: Figure 2.4—Loss of annual NPP, GL
Page 34 and 35: Figure 2.7—Annual loss of NPP in
Page 36 and 37: Table 2.2—Nitrogen application ra
Page 38 and 39: Figure 2.12—Areas affected by hum
Page 40 and 41: output—which is a selection of su
Page 42 and 43: GLADIS also underlines the linkage
Page 44 and 45: Box 2.2—Continued A map on global
Page 46 and 47: Table 2.3—Global land degradation
Page 48 and 49: Table 2.3—Continued Project and d
Page 50 and 51: Table 2.4—Continued Location 10 2
Page 52 and 53: Table 2.6—Extent and severity of
Page 54 and 55: National Level Policies As discusse
Page 56 and 57: Such support has also been directed
Page 58 and 59: Migration, either as outmigration o
Page 60 and 61: The preceding discussion shows the
Page 62 and 63: Results Correlation Analysis Consis
Page 64 and 65: Figure 2.23—Relationship between
Page 66 and 67: Effects of Land Degradation On-Site
Page 68 and 69: soils and higher land productivity.
Page 70 and 71: Acknowledging the work of GLADIS, a
Page 72 and 73: health, education, security, enviro
Page 74 and 75: Box 3.1—Recent major economic ass
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An appropriate economic tool for a
Page 78 and 79:
Figure 3.4—Cost of action and cos
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enefit—for example, income. This
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Figure 3.6—Ecosystem services fra
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Replacement Cost Approaches The rep
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Box 3.2—Measuring land degradatio
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land degradation and conservation m
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Flooding and Aquifer Recharge Richa
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year (Diao and Sarpong 2007). Sonne
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Bringing together the different cos
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This section discusses the most imp
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governing land use patterns (Leeman
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promotion of community forest manag
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Box 4.3—Reducing emissions from d
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Soil Nutrient Depletion Soil nutrie
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that the yields of salt-tolerant wh
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Figure 5.3—Forest area as a perce
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Figure 5.5—Per capita water stora
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Introduction 6. CASE STUDIES Five c
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Salinity The effects of salinity on
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Third, to correctly decide which ac
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Costs of Action and Inaction We eva
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The NGOs and religious organization
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have a strong influence on NRM (And
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We estimated the cost of action (de
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Figure 6.15—Costs of action and i
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Of interest to us is the strategy t
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7. PARTNERSHIP CONCEPT The review o
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degradation. All this should be don
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Finally, the global assessment of D
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the experience of and lessons learn
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Table 7.3—Example of E-DLDD resea
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8. CONCLUSIONS Since the publicatio
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lowest in the region. From a socioe
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Table A.1—Land degradation assess
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Table A.2—Continued Author Region
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Table A.3—Continued Author Countr
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Table A.5—Costs of land degradati
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Figure B.1—Land use systems of th
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REFERENCES Abelson, P. 1979. Cost B
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Benin S., E. Nkonya, G. Okecho, J.
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Clark, E. H. 1985. The Off-Site Cos
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De Jager a., D. Onduru and C. Walag
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Foster, V., and C. Briceño-Garmend
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Holden, S. and H. Lofgren. 2005. As
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Lapar, M. L., and S. Pandey. 1999.
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Nachtergaele, F., M. Petri, R. Bian
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Pender, J. L. 2009. “Food Crisis
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Sauer, J., and H. Tchale. 2006. Alt
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Tan, Z. X., R. Lal, and K. D. Wiebe
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———. 2010. “Assessment of L
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RECENT IFPRI DISCUSSION PAPERS For
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