Falling Water Tables

Half the world's population lives in countries where water tables are falling and wells are going dry.

The big three grain producers-china, India and the United States, which account for nearly half the world grain harvest-are showing falling water tables and drying wells due to overpumping. Other countries where underground aquifers are being overpumped include Iran, Israel, Mexico, Pakistan, Saudi Arabia and Yemen. The population in countries where wells are drying up will increase by nearly 3 billion people by 2050.

Despite depressed prices for wheat and corn, the world price for rice -- a crop particularly vulnerable to water shortages -- has climbed by more than 30 percent to $260 a ton in the last year, according to government figures. In the Philippines temperatures rose an average of 2 degrees between 1979 and 2003. In research published by the National Academy of Sciences last year, a team of nine scientists concluded that rice yields typically decline by 10 percent with each 2-degree Fahrenheit increase in temperature during the growing season.