World agriculture towards 2030/2050: the 2012 revision - Fao

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PROOF COPY cropping calendars (see Hoogeveen, 2012 for an explanation of the methodology applied, a summary of which is also given in Bruinsma, 2011). However, it is water withdrawal for irrigation, i.e. the volume of water extracted from rivers, lakes and aquifers for irrigation purposes, which is generally used to measure the impact of irrigation on water resources. Irrigation water withdrawal normally far exceeds the consumptive water use in irrigation because of water lost during transport and distribution from its source to the crops. In addition, in the case of rice irrigation, additional water is used for paddy field flooding to facilitate land preparation and for plant protection and weed control. Irrigation efficiency (here below termed water use efficiency) can be defined as the ratio between the crop water requirements, estimated as consumptive water use in irrigation plus water needed for land preparation and weed control in the case of paddy rice, and irrigation water withdrawal. Data on country water withdrawal for irrigation has been collected in the framework of the AQUASTAT programme. Comparison of these data with the consumptive use of irrigation was used to estimate water use efficiency 76 at the country level. For the world, it is estimated that the average water use efficiency was around 50 percent in 2005/07, varying from 25 percent in areas of abundant water resources such as sub-Saharan Africa to 58 percent in South Asia where water scarcity calls for higher efficiencies (Table 4.11). To estimate the irrigation water withdrawal in 2050, an assumption had to be made about possible developments in the water use efficiency (WUE) in each country. Unfortunately, there is little empirical evidence on which to base such an assumption. Two factors, however, will have an impact on the development of the water use efficiency: the estimated levels of water use efficiency in the base year and water scarcity 77 . A function was designed to capture the influence of these two parameters, bearing in mind that improving water use efficiency is a very slow and difficult process 78 . The overall result is that efficiency could increase marginally at the global level and in water rich regions, but more so in water scarce regions and countries (e.g. a 9 percentage point increase in the Near East/North Africa region; Table 4.11). Indeed, it is expected that, under pressure from limited water resources and competition from other uses, demand management will play an important role in improving water use efficiency in water scarce regions. In contrast, in humid areas the issue of water use efficiency is much less relevant and is likely to receive little attention. At the global level irrigation water withdrawal is expected to grow by about 6 percent, from the current 2760 79 km3/yr to 2926 km3/yr in 2050 80 (Table 4.11). The 6 percent increase in irrigation water withdrawal should be seen against the projected 12 percent increase in the 76 It should be noted that although the term ‘water use efficiency’ implies losses of water between source and destination, not all of this water is actually lost as much flows back into the river basin and aquifers and can be re-used for irrigation. 77 Water scarcity or ‘stress’ measured as consumptive water use in irrigation as a percentage of renewable water resources. 78 WUE was estimated across countries as: WUE = (country-specific intercept) – (1 / (1 + 1.85 * Stress )) 79 The estimated 2760 km3/yr is based on an estimated 1380 km3/yr consumptive water use and an average water use efficiency of 50 percent. The 1380 km3 consists of an 1190 km3 water consumption in irrigation (which is very close to the 1180 km3 estimated by Siebert and Döll (2009) for 1998-2002), and of an 190 km3 needed to flood rice paddy fields (94.3 million irrigated rice area in 2005/07 flooded with on average 20 cm of water). 80 A recent report from the OECD (OECD, 2012) estimates fresh water use in irrigation in 2000 at 2384 km3/yr (accounting for 67 percent of total fresh water use) and expects irrigation water use to fall by 2050 to 2049 km3/yr (37 percent of total fresh water use) mainly on account of fierce competition for fresh water from the industrial and domestic sectors. 123
PROOF COPY harvested irrigated area (from 326 million ha in 2005/07 to 365 million ha in 2050; Table 4.9). This difference is in part explained by the expected improvement in water use efficiency, leading to a reduction in irrigation water withdrawal per irrigated hectare, and in part due to changes in cropping patterns for some countries such as China, where a substantial shift in the irrigated area from rice to maize production is expected. Due to its high water needs for flooding, the expected decline in the irrigated area allocated to rice, in particular in South and East Asia, is an important factor in limiting water demand. Globally it could fall from 94.3 million ha in 2005/07 to 89.5 million ha in 2050, which alone would account for over 10 km3/yr decline in water withdrawals. Irrigated rice area declines are estimated as from 30.6 to 24.0 million ha in South Asia and from 53.5 to 52.7 million ha in East Asia (after peaking at 57.5 million ha in 2030). Table 4.11 Annual renewable water resources and irrigation water withdrawal Renewable water resources* Water use efficiency ratio 2005/ 2007 2050 2005/ 2007 Irrigation water withdrawal 2050 2005/ 2007 Pressure on water resources due to irrigation cubic km percent cubic km percent World 42 000 50 51 2 761 2 926 6.6 7.0 Developed countries 14 000 41 42 550 560 3.9 4.0 Developing countries 28 000 52 53 2 211 2 366 7.9 8.5 Sub-Saharan Africa 3 500 25 30 96 133 2.7 3.8 Latin America 13 500 42 42 183 214 1.4 1.6 Near East/North Africa 600 56 65 311 325 51.8 54.1 South Asia 2 300 58 58 913 896 39.7 38.9 East Asia 8 600 49 50 708 799 8.2 9.3 * includes at the regional level ‘incoming flows’. Irrigation water withdrawal in 2005/07 was estimated to account for only 6.6 percent of total renewable water resources in the world (Table 4.11). However, there are wide variations between countries and regions, with the Near East/North Africa region using 52 percent of its renewable water resources in irrigation while Latin America barely uses 1.4 percent of its resources. At the country level, variations are even more pronounced. In the base year (2005/07), 13 countries used already more than 40 percent of their water resources for irrigation, a situation which can be considered critical. An additional 9 countries consumed more than 20 percent of their renewable water resources, a threshold sometimes used to indicate impending water scarcity. The situation would worsen over the period to 2050, with two more countries crossing the 40 percent and another country the 20 percent threshold. If one would add the expected additional water withdrawals needed for non-agricultural use, the picture would not change much since agriculture represents the bulk of water withdrawal. Nevertheless, for several countries, relatively low national figures may give an overly optimistic impression of the level of water stress: China, for instance, is facing severe water shortage in the north while the south still has abundant water resources. Already in 2005/07, four countries (Libya, Saudi Arabia, Yemen and Egypt) used volumes of water for irrigation 2050 124
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WORLD AGRICULTURE TOWARDS 2030/2050
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Acknowledgements PROOF COPY This pa
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Boxes PROOF COPY Box 1.1 Measuring
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PROOF COPY Figure A.2.1.6 India: fo
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PROOF COPY producing countries rema
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PROOF COPY may fall from 2.3 billio
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PROOF COPY Minimum Dietary Energy R
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PROOF COPY Concerning the main prod
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PROOF COPY vegetable oil imports fo
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PROOF COPY constraints can be signi
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PROOF COPY Figure 1.8 Irrigated are
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PROOF COPY Figure 1.9 World cereals
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PROOF COPY for both food and non-fo
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PROOF COPY 2050, reaching a peak of
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PROOF COPY 436 million in the over
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PROOF COPY CHAPTER 2 PROSPECTS FOR
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PROOF COPY Figure 2.1 kcal/person/d
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PROOF COPY The FAO estimates of und
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PROOF COPY by people. In particular
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PROOF COPY production potential. Th
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PROOF COPY Table: Growth in Populat
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PROOF COPY (Figure2.6), at 7.4 bill
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PROOF COPY Table 2.4 GDP assumption
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PROOF COPY Modest reductions in the
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PROOF COPY Such optimism notwithsta
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PROOF COPY in North Africa have hig
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PROOF COPY (which in our data appea
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PROOF COPY The other major commodit
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PROOF COPY Table 2.6 Changes in the
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PROOF COPY • Despite this slow pa
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PROOF COPY undernourishment and the
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PROOF COPY commodities and waste. F
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PROOF COPY Where does this leave us
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PROOF COPY Figure A.2.1.6 shows the
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PROOF COPY cereals for ethanol 41 .
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PROOF COPY consumption was heavily
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PROOF COPY Figure 3.2 Net agricultu
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PROOF COPY It is noted, however, th
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PROOF COPY Figure 3.4 Per capita fo
Page 79 and 80: PROOF COPY 2005/07. 45 Not all of t
Page 81 and 82: PROOF COPY Table 3.3 Net trade bala
Page 83 and 84: PROOF COPY growth in the ruminant s
Page 85 and 86: PROOF COPY Table 3.4 Meat: aggregat
Page 87 and 88: PROOF COPY countries in per capita
Page 89 and 90: PROOF COPY associated with such lar
Page 91 and 92: PROOF COPY Figure 3.8 World feed us
Page 93 and 94: PROOF COPY The production of biodie
Page 95 and 96: PROOF COPY the exports of the two m
Page 97 and 98: 3.5 Roots, tubers and plantains 3.5
Page 99 and 100: PROOF COPY the two factors that mak
Page 101 and 102: PROOF COPY Net exports from develop
Page 103 and 104: PROOF COPY Figure 3.14 Sugar net tr
Page 105 and 106: PROOF COPY Climate change In evalua
Page 107 and 108: PROOF COPY Table 4.1 Increases in p
Page 109 and 110: PROOF COPY involved are considerabl
Page 111 and 112: PROOF COPY cropping intensities (6
Page 113 and 114: PROOF COPY No data exist on total h
Page 115 and 116: PROOF COPY Box 4.2 Agro-ecological
Page 117 and 118: PROOF COPY under cultivation. It is
Page 119 and 120: PROOF COPY products facing finite n
Page 121 and 122: PROOF COPY place in sub-Saharan Afr
Page 123 and 124: PROOF COPY The bulk of arable land
Page 125 and 126: PROOF COPY Figure 4.7 Area equipped
Page 127 and 128: PROOF COPY The developed countries
Page 129: PROOF COPY 4.2.5 Irrigation water r
Page 133 and 134: PROOF COPY Figure 4.10 Annual growt
Page 135 and 136: PROOF COPY million ha at an average
Page 137 and 138: PROOF COPY producers 81 are about h
Page 139 and 140: PROOF COPY the often unfavourable a
Page 141 and 142: PROOF COPY Table 4.15 Fertilizer co
Page 143 and 144: PROOF COPY under way for some time,
Page 145 and 146: PROOF COPY Livestock production is
Page 147 and 148: Argentina Bolivia (Plurinational St
Page 149 and 150: Wheat Rice Maize Barley Millet Sorg
Page 151 and 152: PROOF COPY and yields by irrigated
Page 153 and 154: PROOF COPY References Alexandratos,
Page 155 and 156: PROOF COPY FAO (1996), Food, Agricu
Page 157 and 158: PROOF COPY Ma, Hengyun, Jikun Huang
Page 159 and 160: PROOF COPY van der Mensbrugghe, D.,
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