Parking lots are coming under fire from environmentalists. The lots can’t absorb rain, so water runs off the pavement, carrying pollution and causing erosion. At the same time, the lots absorb heat from sunlight, releasing it at night and raising temperatures in urban areas from six to 12 degrees compared to nearby rural areas. The increased heat in turn pushes people to turn up their air conditioners and drive rather than do errands on foot. As alternatives or improvements, enviros and municipal officials recommend parking garages, which take up less ground; white concrete, which doesn’t heat up as much; and islands of trees and shrubs in parking lots.