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 challenge is either to build an economy that is sustainable or to stay with our unsustainable economy until it declines. It is not a goal that can be compromised. One way or another, the choice will be made by our generation, but it will affect life on earth for all generations to come.

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.

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

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.

Population growth is exceeding farmers' ability to keep up...Our oldest enemy, hunger, is again at the door.

The throwaway economy that has been evolving over the last half-century is an aberration, now itself headed for the junk heap of history.