Sustainable agriculture is more complex and

Impacts of AKST on Development and Sustainability Goals | 151 increasingly by small-scale private investments. Irrigation was essential to achieving the gains from high-yielding fertilizer-responsive crop varieties. Approximately 70 of the world’s irrigated land is in Asia Brown, 2005, where it accounts for almost 35 of cultivated land Molden et al., 2007a. Forty percent of the world cereal production is from irrigated land and as much as 80 of China’s grain harvest comes from irrigated land. By contrast, there is very little irrigation in sub-Saharan Africa. Trends have changed from the 1970s and early 1980s when donor spending on agricultural water reached a peak of more than US1 bil- lion a year. Funding fell to less than half that level by the late 1980s; beneit-cost ratios deteriorated; and as falling cereal prices and rising construction costs highlighted the poor performance of large-scale irrigation systems, opposi- tion mounted to the environmental degradation and social dislocation sometimes caused by large dams. Today, there appears to be consensus that the appropriate scale of in- frastructure should be determined by the speciic environ- mental, social, and economic conditions and goals with the participation of all stakeholders Molden et al., 2007a. Increased fertilizer use is closely associated with crop pro- ductivity gains in regions that have been most successful at reducing undernourishment. Goals N, H, L, E, S Certainty A Range of Impacts +2 to +5 Scale G Specificity Especially in Asia On a global scale, total fertilizer consumption has increased from approximately 31 million in 1961 to 142 million tonnes in 2002 FAOSTAT, 2007. From almost no use in the early 1960s, total fertilizer consumption rates in the devel- oping countries of Asia 140 kg ha -1 yr -1 now exceed those in industrialized nations FAOSTAT, 2006 and have been a principal driver of improved crop productivity. In sub- Saharan Africa where cereal productivity has increased only modestly since the 1960s, average fertilizer consumption re- mains exceptionally low—under 20 kg ha -1 yr -1 FAOSTAT, 2006. For cereal crops, approximately 50 of the yield increases observed after the introduction of modern crop The breeding and dissemination of Modern Varieties MV has had a major impact on food production. Goals N, L, D Certainty A Range of Impacts -2 to +5 Scale G Specificity Widespread applicability The breeding and dissemination of Modern Varieties with greater yield potential, better pest and disease resistance and improved organoleptic quality have, in conjunction with irrigation, fertilizer, pesticides and mechanization, had a major impact on food production Figure 3-1. Modern Varieties, especially of cereals but also of root, protein and horticultural crops, have been widely adopted; Asia grows modern cereal varieties on 60-80 of the cultivated area Evenson and Gollin, 2003a. Modern Varieties are also widely grown in Latin America but there has been less im- pact in sub-Saharan Africa and CWANA. Other than in CWANA there has been little impact of Modern Varieties on protein crops mostly annual legumes. Evidence relating farm size to productivity and efficiency is weak. Goals N, H, L, E, S, D Certainty C Range of Impacts -4 to +4 Scale G Specificity Variable Farms operated by small-scale producers are typically more eficient the smaller they are Feder et al., 1988; Place and Hazell, 1993; Deininger and Castagnini, 2006. However, in large-scale mechanized farming economies of scale are important. For example, some regionally speciic research has concluded that productivity and eficiency are positively related to farm size Yee et al., 2004; Hazarika and Alwang, 2003, although there is also evidence that some large-scale mechanized farms are less eficient than smaller family farms Van Zyl, 1996. The lack of clarity about the rela- tionship between farm size and productivity and eficiency Sender and Johnston, 2004 suggests confounding factors, such as land quality, and access to labor, markets, sources of credit and government farm policies Van Zyl, 1996; Chen, 2004; Gorton and Davidova, 2004. For example, land per capita has been found to be a major determinant of overall household income Jayne et al., 2003. Good management, on large- and small-scale farms, may be the most impor- tant factor affecting production eficiency. Typically, large- scale farmers with inancial resources intensify agrichemi- cal inputs and seek economies of scale, while resource-poor small-scale farmers reduce inputs, diversify, and seek risk aversion Leakey, 2005a. Interestingly, it is often among the latter group that some of the best examples of sustain- able agriculture are found, especially in the tropics Palm et al., 2005b. Globally there has been an extensive increase in irrigated areas, but investment trends are changing. Goals N, E Certainty B Range of Impacts -1 to +5 Scale G Specificity Globally except SSA Since 1961, the area of irrigated land has doubled to 277 million ha in 2000—about 18 of farmed land, fund- ed initially by investments by international development banks, donor agencies, and national governments but later Figure 3-3. Trend in nitrogen fertilizer efficiency of crop production calculated as annual global cereal productionannual global application of N. Source: Tilman et al., 2002. 152 | IAASTD Global Report eficiency change contributing 0.9 and technical change 1.2 Coelli and Rao, 2003. The highest growth was ob- served in Asia e.g., China 6 and North America and the lowest in South America followed by Europe and Africa. However, a positive trend does not necessarily imply a sus- tainable system since rapid productivity gains from new technologies may mask the effects of serious resource deg- radation caused by technology-led intensiication, at least in the short to medium-term Ali and Byerlee, 2002. 3.2.1.1.2 Agriculture has impacts on natural capital and resource quality In regions with the highest rates of rural poverty and un- dernourishment, depletion of soil nutrients is a pervasive and serious constraint to sustaining agricultural produc- tivity. Goals N, H, L, E, S, D Certainty A Range of Impacts -1 to -5 Scale R Specificity SSA, ESAP To sustain long-term agricultural production, nutrients ex- ported from the agroecosystem by harvest and through en- vironmental pathways e.g., leaching, erosion must be sufi- ciently balanced by nutrient inputs e.g., fertilizer, compost, atmospheric deposition, in situ biological nitrogen ixation. In the tropical countries where shifting agriculture is the traditional approach to regenerating soil fertility, increas- ing population pressure has resulted in shorter periods of fallow and often severe reductions in soil stocks of organic carbon and nutrients Palm et al., 2005a. Nutrient deple- tion is particularly acute in many of the continuous cereal production systems on the Indian sub-Continent, Southeast Asia, and sub-Saharan Africa, especially since many of the soils in these regions have low native fertility Cassman et al., 2005. With reduced land availability for fallows, low use of fertilizer amendments, and in some circumstances high rates of erosion, many soils in sub-Saharan Africa are highly degraded with respect to nutrient supply capacity Lal, 2006; Vanlauwe and Giller, 2006. It has been esti- mated that 85 of the arable land in Africa ca. 185 million ha has net depletion rates of nitrogen, phosphorous and potassium NPK that exceed 30 kg ha -1 yr -1 Henao and Baanante, 2006 with 21 countries having NPK depletion rates in excess of 60 kg ha -1 yr -1 . In high-yielding agriculture, the application of modern production technologies is often associated with environ- mental damage. In some cases, this damage is most attrib- uted to inappropriate policies and management practices rather than to the technologies per se. Goals E Certainty B Range of Impacts 0 to -5 Scale G Specificity Widespread The adoption of MVs and yield enhancing technologies like inorganic fertilizer use and irrigation have been linked to a loss of biodiversity, reduced soil fertility, increased vulnera- bility to pestsdiseases, declining water tables and increased salinity, increased water pollution, and damage to fragile lands through expansion of cropping into unsuitable areas. A detailed assessment of the environmental impacts asso- varieties in countries such as India can be attributed to in- creased fertilizer use Bruinsma, 2003. However, there is also evidence of declining eficiency of nitrogen applications in cropping systems Figure 3-3. Tractors and other sources of mechanization are increas- ingly important to agriculture in developing countries, but many systems remain dependent on traditional forms of human and animal power. Goals N, H, L, E, S, D Certainty B Range of Impacts -1 to +3 Scale G Specificity Developing countries In developing countries, human, draft animal, and tractor power are used in approximately equivalent proportions in terms of total land under cultivation. There are, however, signiicant differences between and within countries and be- tween regions and different types of agricultural systems. In SSA, about two-thirds of all agricultural land is cultivated by hand, whereas in LAC approximately 50 of the land is mechanically cultivated Bruinsma, 2003. Although it is dificult to directly establish cause and effect relationships between single classes of assets and human welfare, it is generally recognized that households with animal or me- chanical power tend to have better crop yields, more oppor- tunities to pursue off-farm employment, and greater food security Bishop-Sambrook, 2004. Pesticide use is increasing on a global scale, but increases are not universally observed; several of the most hazardous materials are being phased out in well-regulated markets. Goals N, H, L, E, S, D Certainty C Range of Impacts -5 to +4 Scale G Specificity Developed and developing countries In constant dollars, global expenditures on agricultural pes- ticide imports has increased more than 1000 since 1960 Tilman et al., 2001 with some estimates placing recent growth rates for pesticide use at between 4.0 and 5.4 per annum Yudelman et al., 1998. There are exceptions to these trends, particularly in OECD countries. For example, in the US, agricultural pesticide use declined signiicantly after peaking in the late 1970s and has remained relatively constant since the 1990s Aspelin, 2003. Moreover, regula- tory and technological advances have, in some cases, result- ed in the phase-out of particularly toxic organic compounds and the introduction of pesticides with lower non-target toxicity, which are less persistent in the environment and can be applied at lower rates Aspelin, 2003; MA, 2005. Total factor productivity has increased worldwide, with some regional variation. Goals D Certainty C Range of Impacts -1 to +3 Scale G Specificity Especially in intensive systems Total Factor Productivity TFP, i.e., the eficiency with which all the factors of agricultural production land, wa- ter, fertilizer, labor, etc. are utilized, has improved over the last ifty years Coelli and Rao, 2003. The index of TFP for world agriculture has increased from 100 in 1980 to 180 in 2000. The average increase in TFP was 2.1 per year, with