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.

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.

We can build an economy that does not destroy its natural support systems, a global community where the basic needs of all the Earth's people are satisfied, and a world that will allow us to think of ourselves as civilized. This is entirely doable.

One way or another, the choice will be made by our generation, but it will affect life on earth for all generations to come

Saving Greenland is both a metaphor and a precondition for saving civilization. If its ice sheet melts, sea levels will rise 23 feet. Hundreds of coastal cities will be abandoned. The rice growing river deltas of Asia will be under water. There will be hundreds of millions of rising-sea refuges. The word that comes to mind is chaos. If we cannot mobilize to save the Greenland ice sheet; we probably cannot save civilization as we know it.

Children whose developing lungs are particularly vulnerable suffer the most from air pollution. For children, breathing the air in cities with the worst pollution, such as Beijing, Calcutta, Mexico City, Shanghai, and Tehran, is equivalent to smoking two packs of cigarettes a day.

The foundation is being laid for the emergence of both wind and solar cells as cornerstones of the new energy economy.