Humanity's greatest challenge may soon be just making it to the next harvest.

The biggest threat to global stability is the potential for food crises in poor countries to cause government collapse.

In this era of tightening world food supplies, the ability to grow food is fast becoming a new form of geopolitical leverage, and countries are scrambling to secure their own parochial interests at the expense of the common good.

In the Middle East, where populations are growing fast, the world is seeing the first collision between population growth and water supply at the regional level. For the first time in history, grain production is dropping in a geographic region with nothing in sight to arrest the decline. Each day now brings 10,000 more people to feed and less irrigation water with which to feed them.

Rising oil prices have focused the world's attention on the depletion of oil reserves. But the depletion of underground water resources from overpumping is a far more serious issue. Excessive pumping for irrigation to satisfy food needs today almost guarantees a decline in food production tomorrow.

A sustainable economy represents nothing less than a higher social order one as concerned with future generations as with our own, and more focused on the health of the planet and the poor than on material acquisitions and military might. While it is a fundamentally new endeavor, with many uncertainties, it is far less risky than continuing with business as usual.

No civilization has survived the ongoing destruction of its natural support systems. Nor will ours.