Major rivers including the Colorado, Amu Darya, and the Yellow are running dry. Water shortages are affecting grain trading routes and shaping the future of world food shortage. Another problem facing food supply is a finite amount of land. Several causes of land shortage are construction of housing, soil erosion and land degradation, population growth and lost momentum in raising land productivity. Land scarcity could affect many areas of human activity including transportation policy and recreation.
Malnutrition is the most visible and problematic effect of land and water shortage.
Overfed and underfed people face similar health problems. They suffer from an increased susceptibility to illness, reduced life expectancy and reduced productivity. There are 600 million overweight people world wide. 97 million of those are adults in the United States. The industrialized nations have experienced the greatest increase in the share of population that is overweight.