Yet, most of the readily accessible reserves of oil formed over hundreds of millions of years will be consumed within a single generation, spanning the years from 1960 to 1995.

Our early 21st century civilization is in trouble. We need not go beyond the world food economy to see this. Over the last few decades we have created a food production bubble-one based on environmental trends that cannot be sustained, including overpumping aquifers, overplowing land, and overloading the atmosphere with carbon dioxide.

It takes 1,000 tons of water to produce 1 ton of grain. As water becomes scarce and countries are forced to divert irrigation water to cities and industry, they will import more grain. As they do so, water scarcity will be transmitted across national borders via the grain trade. Aquifer depletion is a largely invisible threat, but that does not make it any less real.

Nations are in effect ceding portions of their sovereignty to the international community and beginning to create a new system of international environmental governance.

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

The 20th century was the time when the world turned to use of fossil fuels and the 21st century will be the century of the renewables.

Today, more than ever, we need political leaders who can see the big picture, who understand the relationship between the economy and its environmental support systems.