The world must double its agricultural production by 2050 (http://www.weforum.org/issues/agriculture-and-food-security) when the human population is predicted to reach 9.3 billion (http://esa.un.org/unpd/wpp/index.htm). If only freshwater was as available as is light. While both these resources are unevenly distributed, the 120,000 terawatts of solar energy that the earth receives is unlikely to be the major limiting factor in plant production – crops harvest only a very small fraction of this energy. In contrast, water availability will undoubtedly be one of the problems for future food production. Currently, 70% of fresh water usage is devoted to agriculture (http://www.fao.orgr/water/aquastat/water_use/index.stm). It does not take a genius to realise that increasing food production will put enormous strain on a scarcer and scarcer resource. The profligate way that water is used today (at least in most countries) is similar to the way electricity was used 100 years ago. But supposing we used water with the same sophistication as we now use electricity?
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