There are a number of reasons for these bleak trends, but none is more powerful than the way that we have allowed our metropolitan regions to grow. Greater Chicago, for example, has grown in the last twenty years in area at a rate ten times faster than its growth in population. The developed area of greater Cleveland has grown some 43 percent in the last decade, even while the region's overall population has decreased. Metropolitan Phoenix now reaches to an area equivalent to Delaware. With ever-outward sprawl, destinations become farther and farther apart.
Communities become unsuitable for walking.
New suburban densities become too low to support regular transit service. Driving can only go up and up. Energy use rises directly with increased driving, exacerbating fossil fuel dependence and global warming. Increased vehicle use also is projected to exacerbate air pollution to the extent that, in the next decade, progress made because of improvements in vehicle technology will be reversed. Farmland, wildlife habitat, and valuable open space are paved over.