What was once a relatively small stream of resources flowing into early cities, however, has in this century become a deluge. To satisfy resource-hungry human colonies, land is often stripped bare or trampled, or overgrazed, soil is subjected to erosion, and farmland is transformed into desert. Cities and suburbs also produce sizable amounts of waste. Air pollution, hazardous waste, sewage sludge, garbage, and other wastes pour out of our cities, far in excess of the environments s ability to assimilate them, threatening not only the health of urban inhabitants but the health of the entire biosphere. The problem with human colonies is that they violate the conditions required for sustainability.
Metropolitan areas are out of balance with the environment upon which they depend . . .
The ever persistent spread of cities will continue to devour valuable farmland, forests, and pasture. Gobbling up land and polluting the water and air upon which all life depends, our cities are on a collision course with the future. Redevelopable and infill sites should develop under utilized parcels with new uses that allow them to function as walkable, mixed-use districts. Existing uses which are complementary, economical, and physically viable, should be integrated into the form and function of the neighborhood. In addition, much of the development that has taken place in the past thirty or forty years tends to be deliberately isolated, monofunctional and auto-dependent.