Projections for the future

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Seckler et al. (1999) estimates that by 2025 cereal production will have to increase by 38% to meet world food demands. The World Water Vision, an outcome of the Second World Water Forum in The Hague in 2000, estimated a similar increase of 40% based on various projections and modelling exercises. These figures are based on an econometric model showing that grain production will increase about 2% per year for the 2000-2020 period (Koyama, 1998). Following UN mid-range population estimates of 8.9 billion people, combined with the minimum caloric requirement of 2200 calories per day, means that a total of about 20 trillion consumable calories have to be produced. Current levels are at about 14 trillion calories, which means an increase of 42% is needed. However, given the range in population estimates provided by the UN, this figure can be between 14% and 71%.

The increase in food production and related water requirements coincides with an alarming increase in water scarcity. One-third of the world's total population of 5.7 billion lives under conditions of relative water scarcity and 450 million people are living under severe water stress (UNEP, 1998). This relative water scarcity and severe water stress are defined using the Relative Water Demand (RWD), expressed as the fraction of water demand over water supply. A RWD larger than 0.2 indicates relative water scarcity, while a RWD greater than 0.4 indicates severe water stress. However, the UN values are based on national-level totals, ignoring the fact that especially in bigger countries, huge spatial differences can occur. Vorosmarty et al. (2000) show that, including these in-country differences, 1.8 billion people live in areas with severe water stress. Using a global water model and projections for climate change, population growth and economic growth, they concluded that the number of people living in severe water stress will have grown to 2.2 billion by the year 2025.

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