There are about 7 billion people in the world. With an estimated 868 million hungry people, 12 percent, or 1 in 8 people, are hungry.
The Intergovernmental Panel on Climate Change predicts yields from rain-dependent agriculture could be down by 50 percent by 2020.
Climate change could force an additional 1.8 billion people to live in a water scarce environment by 2080
There is evidence that the global climate is changing. A global temperature increase of 3-4°C could cause changed run-off patterns and glacial melt will force an additional 1.8 billion people to live in a water scarce environment by 2080.
Climate change is predicted to have a whole range of impacts on water resources. Variation in temperature and rainfall may affect water availability, increase the frequency and severity of floods and droughts, and disrupt ecosystems that maintain water quality.
Irrigation increases yields of most crops by 100 to 400 percent, and irrigated agriculture currently contributes to 40 percent of the world's food production on 20 percent of the cultivated land.
The daily drinking water requirement per person is 2-4 litres, but it takes 2 000 to 5 000 litres of water to produce one person's daily food.
Global population growth projections of 2–3 billion people over the next 40 years, combined with changing diets, result in a predicted increase in food demand of 60 % by 2050. Future global agricultural water consumption (including both rainfed and irrigated agriculture) is expected to increase by 19 percent (to 8 515 km3 per year) in the same period.
Diets are shifting from predominantly starch-based food to meat and dairy, which requires more water. Meat consumption in particular is expected to rise from 37 kg per person per year in 1999/2001 to 52 kg in 2050 (from 27 to 44 kg in developing countries), implying that much of the additional crop production will be used as feed for livestock production. This dietary shift has had the greatest impact on water use over the past 30 years, and is likely to continue well into the middle of the twenty-first century.
By 2050, rising populations in flood-prone lands, climate change, deforestation, loss of wetlands and rising sea levels are expected to increase the number of people vulnerable to flood disaster to 2 billion.