* Photo: Offer Wolberger * To many Americans, ecological nirvana is a bucolic existence surrounded by wilderness. But the Thoreauvian desire for more elbow room has led to sprawl, malls, and cougar attacks. The edge-city upshot is a national cadre of 3.5 million "extreme commuters," who spend more than three hours a day in transit, many of them spewing carbon dioxide between exurb home and city office. Automobile exhaust in the US contributes roughly 1.9 billion tons a year to the global carbon cloud, more than the emissions of India, Japan, or Russia. Even worse are the 40 million lawn mowers used to tame the suburban backcountry: Each spews 11 cars' worth of pollutants per hour.

The fact is, urban living is kinder to the planet, and Manhattan is perhaps the greenest place in the US. A Manhattanite's carbon footprint is 30 percent smaller than the average American's. The rate of car ownership is among the lowest in the country; 65 percent of the population walks, bikes, or rides mass transit to work. Large apartment buildings are the most efficient dwellings to heat and cool.

And guess what high-speed means of transportation emits less atmospheric carbon than trains, planes, and automobiles? The humble counterweight elevator put into service in 1857, which has made vertical density possible from Dubai to Taipei.

Related Inconvenient Truths: Get Ready to Rethink What it Means to Be Green 1: Live in Cities 2: A/C Is OK 3: Organics Are Not The Answer 4: Farm the Forests 5: China Is the Solution 6: Accept Genetic Engineering 7: Carbon Trading Doesn't Work 8: Embrace Nuclear Power 9: Used Cars — Not Hybrids 10: Prepare for the Worst