The Environmental Food Crisis
Water is essential not only to survival but is also equally or even more important than nutrients in food production. Agriculture ac- counts for nearly 70% of the water consumption, with some es- timates as high as 85% (Hanasaki et al ., 2008a,b). Water scarcity will affect over 1.8 billion people by 2025 (WHO, 2007). This could have major impacts on health, particularly in rural areas, and thus also major impacts on farmer productivity. Although of great sig- nificance, such indirect effects are not considered here. Current projections suggest that water demand is likely to double by 2050 (Figure 20). Estimates project water withdrawals to increase by 22– 32% by 2025 (De Fraiture et al ., 2003) and nearly double by 2050, for all SRES scenarios (Shen et al ., 2008). For poor countries with rapid population growth and depletion of groundwater, water-defi- cit induced food insecurity is a growing problem (Rosegrant and Cai, 2002; Yang et al ., 2003). One major factor beyond agricultural, industrial and urban consumption of water is the destruction of watersheds and natural water towers, such as forests in watersheds and wetlands, which also serve as flood buffers (UNEP, 2005). IMPACTS OF WATER SCARCITY ON YIELD
Studies of 128major river basins and drainage regions show that approximately 20 to 50% of the mean annual river flow in different basins needs to be allocated to freshwater-de- pendent ecosystems in order to maintain them in good eco- logical condition. In large parts of Asia and North Africa and some parts of Australia, North America and Europe, current total direct water withdrawals (primarily for irriga- tion) already tap into the estimated environmental water re- quirements (Smakhtin et al ., 2004). The global consump- tion of both “blue’’ water (withdrawn for irrigation from rivers, lakes and aquifers) and “green’’ water (precipitation) by rainfed and irrigated agriculture and other terrestrial ecosystems is steadily rising (Rost et al ., 2008). Water is probably one of the most limiting factors in increas- ing food production. Yields on irrigated croplands are, on average, 2–3 times higher than those on rainfed lands. Ir- rigated land currently produces 40% of the world’s food on 17% of its land (FAO, 1999), most of it downstream and de- pendent upon glacial and snowmelt from the Hindu Kush Himalayas. It is evident that in regions where snow and glacial mass are the primary sources of water for irrigation, such as in Central Asia, parts of the Himalayas Hindu Kush, China, India, Pakistan and parts of the Andes, melting will eventually lead to dramatic declines in the water available for irrigation, and hence, food production (Figure 21). The melting glaciers will impact certain countries more than others, and also substantially impact hydropower production. The Indus River and its tributaries, for example, in addition to providing nearly 60% of the water utilized for irrigation, also provide 45% of the electrical energy in Pakistan. Of great importance, therefore, is the effect of climate change on the extent of snow and glacial mass (UNEP, 2007) and on the subsequent supply of water for irrigation. Climate change could seriously endanger the current food produc- tion potential, such as in the Greater Himalayas Hindu Kush region and in Central Asia (Figure 21). Currently, nearly 35% of the crop production in Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal and Pakistan is based on ir- rigation, sustaining over 2.5 billion people. Here, water de- mand is projected to increase by at least 70–90% by 2050.
Water requirements for food production (km 3 /year)
Increases, over 2002 water requirements,
Increase, over 2002 water requirements, needed to meet the 2015 hunger target needed to eradicate poverty by 2030 and 2050 respectively
Figure 20: Historic and projected changes in water consumption for food production, 1960-2050. (Source: ).
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