The Economics of Desertification, Land Degradation, and Drought

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Table 2.6—Extent and severity of global soil nutrient depletion, 1990–1999 (in million hectares) Location Light Moderate Strong Total % of total Africa 20.4 18.8 6.2 45.4 34 Asia 4.6 9.0 1.0 14.6 11 South America 24.6 34.1 12.7 71.4 53 Other regions 2.8 1.2 0 3.9 3 Globe 52.4 63.1 19.9 135.3 Source: Tan, Lal, and Wiebe 2005. Biological processes include rangeland degradation, deforestation, and loss in biodiversity, including loss of soil organic matter (which also affects the physical and chemical properties of the soil) or of flora and fauna populations or species in the soil (such as earthworms, termites, and microorganisms) (Scherr 1999). Vegetation degradation is a long-term loss of natural vegetation, with a decrease in biomass and ground cover of perennial native vegetation (Coxhead and Oygard 2007; Katyal and Vlek 2000). Hence, changes in the structure and botanical composition of plants constitute vegetation degradation, which can also occur naturally due to sparse native vegetation. However, in contrast to induced vegetation degradation, natural degradation is typically gradual and often reversible (Katyal and Vlek 2000). Major causes of the destruction of natural vegetation are fires, the use of heavy machines, fuelwood extraction, and overgrazing by livestock stands (Katyal and Vlek 2000). The destruction of natural vegetation directly leads to reduced residues from plants, leading to organic matter loss (FAO 1994; Stocking and Murnaghan 2005). Vegetation degradation is studied using the NDVI. As reported earlier, Africa south of the equator accounted for the largest loss of vegetation between 1981 and 2003 (Bai et al. 2008b). Causes of Land Degradation Proximate Causes As discussed in the conceptual framework of action and inaction, proximate causes of land degradation are those that directly cause land degradation. These are further divided into biophysical factors and unsustainable land management practices. The biophysical proximate causes of land degradation include topography, land cover, climate, soil erodibility, pests, and diseases. Soil erosion is a function of slope length, land cover, and steepness (Wischemeier 1976; Voortman, Sonneveld and Keyzer 2000). Steep, long slopes are vulnerable to severe water-induced soil erosion if they have poor land cover with no physical barriers to prevent erosion. The severity of water- and wind-induced soil erosion is higher if land clearing is done on mountain slopes. Pests and diseases, such as invasive species, lead to loss of biodiversity, loss of crop and livestock productivity, and other forms of land degradation. Climatic Conditions Climate directly affects terrestrial ecosystems. For example, dry, hot areas are prone to naturally occurring wildfires, which, in turn, lead to soil erosion, loss of biodiversity, carbon emission, and other forms of land degradation. Strong rainstorms lead to flooding and erosion, especially if such rainstorms occur during the dry season in areas with poor land cover. Rainfall patterns such as low and infrequent rainfall and erratic and erosive rainfall (monsoon areas) lead to a low soil-moisture content, which then leads to reduced plant productivity and high runoffs, resulting in erosion and salinization because salts in the soil surface are not leached into deeper soil layers (Safriel and Zafar 2005). Furthermore, droughtprone areas are more likely to be naturally degraded (Barrow 1991). A consequence of elevated levels of carbon dioxide, caused by global warming, is increased drought and desertification events (Ma and Ju 2007). Other consequences of climate change include reduced rainfalls, which lead to changes in land use or to a reduction in land cover due to prolonged droughts (see Box 2.3 for more details). 40
Box 2.3—The relationship between climate change and land degradation Climate change and land degradation are related through the interactions of land surface and the atmosphere. These interactions involve multiple processes, with impact flows running in both directions—from the land surface to the atmosphere and vice versa. These complex processes take place and vary simultaneously (WMO 2005). The feedback effects between climate change and land degradation are not yet fully understood. Climate change affects land degradation because of its longer-term trends and because of its impacts on the occurrence of extreme events and increased climate variability. Climate change trends include the increase in temperature and a change in rainfall patterns, which are two determinants in the creation and evolution of soils, most notably through their impact on vegetation distribution. Climate variability holds the potential for the most severe human impacts. For instance, the occurrence and severity of droughts has been related to actual declines in economic activity, whereas gradual increases in mean temperature have not. In Sub-Saharan Africa, in particular, climate variability will affect growing periods and yields and is expected to intensify land degradation and affect the ability of land management practices to maintain land and water resources (Pender et al. 2009) in the future. However, it must also be noted that climate change is not solely a negative influence on land degradation—for instance, agroclimatic conditions are expected to improve in some areas. Simultaneously, land degradation affects climate change through (1) the direct effects of degradation processes on land surface, which then affects atmospheric circulation patterns, and (2) the effects of land degradation on land use, with land use changes then affecting the climate. In these complex interrelationships between climate change and land degradation, sustainable land and water management (SLWM) can play a crucial mitigating role. Notably, research has already shown the links between soil carbon sequestration and its impacts on climate change and food security (Lal 2004). Soil carbon sequestration transfers atmospheric carbon dioxide in the soils, hence mitigating its climate change impacts. Increasing soil carbon stocks, in turn, has a positive impact on crop productivity, at least past a certain minimum threshold (World Bank 2010, 77). Thus, SLWM practices that sequester large amounts of soil carbon can provide a win–win–win solution in the issues of climate change, land degradation, and some of their human dimensions, such as food security. Examples of such practices include no-till farming, cover crops, manuring, and agroforestry (Lal 2004). The extent of these win–win–win situations and the conditions under which they can be realized are areas that require more systematic research. Just as climate change and variability will affect different regions in different ways, so too will their consequences relating to DLDD vary in general and to specific types of land degradation in particular. Further, the linkages between land and climate systems hold important keys to the valuation of the costs of DLDD and of land conservation or restoration. In some cases, climatic impacts are of sufficient intensity to induce ecological land degradation, or degradation that naturally occurs without human interference. However, anthropogenic activities often trigger or exacerbate such ecological land degradation (Barrow 1991). Topography Steep slopes lead to land degradation. Fragile, easily damaged soils located along steep slopes are often associated with soil erosion if vegetation cover is poor. Lands located in drylands—as well as lowlands close to the sea, exposed coastal zones, or areas prone to extreme weather and geological events (such as volcanic activity, hurricanes, storms, and so on)—show low resilience and are thus vulnerable to erosion, salinization, and other degradation processes (Safriel and Zafar 2005). Unsustainable Land Management Land clearing, overgrazing, cultivation on steep slopes, bush burning, pollution of land and water sources, and soil nutrient mining are among the major forms of unsustainable land management practices. Underlying Causes Policies, institutions, and other socioeconomic factors affect the proximate causes of land degradation. We discuss key underlying causes of land degradation, some of which were discussed earlier. A brief discussion will be given for such factors that have already been discussed. 41
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 26 and 27: Figure 2.1—GLASOD (1991) global a
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 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
Page 76 and 77: An appropriate economic tool for a
Page 78 and 79: Figure 3.4—Cost of action and cos
Page 80 and 81: enefit—for example, income. This
Page 82 and 83: Figure 3.6—Ecosystem services fra
Page 84 and 85: Replacement Cost Approaches The rep
Page 86 and 87: Box 3.2—Measuring land degradatio
Page 88 and 89: land degradation and conservation m
Page 90 and 91: Flooding and Aquifer Recharge Richa
Page 92 and 93: year (Diao and Sarpong 2007). Sonne
Page 94 and 95: Bringing together the different cos
Page 96 and 97: This section discusses the most imp
Page 98 and 99: governing land use patterns (Leeman
Page 100 and 101: promotion of community forest manag
Page 102 and 103:
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
Page 108 and 109:
Figure 5.3—Forest area as a perce
Page 110 and 111:
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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Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
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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