A growing population coupled with diminishing fresh water supplies should force major changes in the way the world's farmers tend their crops in coming decades, a recent study recommends. Since agriculture uses about 70 percent of the globe's fresh water every year, farming should be the focus of intense conservation efforts, Cornell University professor David Pimentel said, according to a Dow Jones report.

"We in the U.S. waste a lot of water in contrast to other people," said Pimentel, whose study appeared in the October issue of the journal BioScience. "Agriculture is going to have to give up water as the population grows," he said. "States like California, Colorado, Texas and Nebraska are going to have to make some major changes."

The study said farmers should use water-conserving irrigation methods combined with water and soil conservation practices to minimize run-off. It also suggests governments eliminate water subsidies to farmers to encourage more efficient use, work to reduce water pollution and protect forests and wetlands.

In parts of Arizona, water from major aquifers is being withdrawn more than 10 times faster than it can be recharged by rainfall. In California, agriculture accounts for about 3 percent of the state's economic production but consumes 85 percent of the fresh water.

"The pace of the problem is proceeding faster than the pace of the solution," Postel said. By 2050, "water will to be the most critical resource issue we face in the entire world," said Bob Stallman, president of the American Farm Bureau Federation and a Texas-based rice farmer. "Frankly, I think wars will be fought over water. There are already border disputes in some parts of the world between countries over water."