Water scarcity is the single biggest threat to global food production. Tensions over water have the potential to incite civil unrest, spur migration, further impoverish already poor regions, destabilize governments, and even ignite armed conflicts.

Irrigation is important because some 40 percent of the world's food now come from the 17 percent of cropland that is irrigated-and we are betting on that share to increase. But, history tells us that irrigation brings serious risks along with its benefits.

Irrigation has been a powerful tool of human advancement for 6,000 years. It remains a cornerstone of agriculture today. Farmers strive to meet the increasing food demands of growing populations. We face the challenge of mounting water scarcity and salinization of soils to rising tensions between countries over shared rivers. The rise and fall of early civilizations can be traced, in many cases, to the failure of irrigated agriculture. Irrigated farmlands are being converted to subdivisions. The water is being converted to municipal uses and the price paid for the right to divert and use the water is ever increasing.

The recent news that 136 miles of the Middle Rio Grande is a protected habitat for the silvery minnow has placed new demands on the finite and overappropriated water of the Middle Rio Grande. This will increase the price of water rights further and faster.

Here are some facts to think about:

1. It takes about 1,000 tons of water to grow one ton of wheat.

2. In the next 25 years, the number of people living in water-stressed areas will increase sixfold to 3 billion.

3. A tenth of the world's grain supply is propped up by unsustainable water use.

4. As water becomes scarce, competition for it is increasing - between neighboring states and countries, between farms and cities, and between people and their environment.

5. Many major rivers now run dry for most of the year.