Harriet Tregoning, director of urban and economic development

Harriet Tregoning, director of urban and economic development at the U.S. Environmental Protection Agency, reports that 94 to 95 percent of development in the U.S. is on “greenfield,”or undeveloped, sites. Even with a tenfold increase in infill (a best-case scenario), 40 percent of growth still will be on greenfield sites 25 years from now. “During the next 20 years we will be able to have a lot of good new urbanist development on greenfield sites,” she says.