You might look in your own backyard. A satellite photo of Salt Lake City, for example, discloses the stark contrast between the downtown neighborhoods and their surroundings. Satellite depiction's of most U.S. metropolitan centers show the same thing. Green space is vanishing while impervious surfaces span our urban landscapes. Man-made urban ecosystems, exploding with little forethought and less control, are dominated by concrete, blacktop and buildings.
Society needs that energy.
Various specialists are attempting to explain problems threatening the world's growing urban populations. Nearly 80 percent of Americans live in urban ecosystems. The world's big cities are growing by a million people a week, while rural populations will be declining in real terms, the World Bank reports. American cities are losing an average four trees for every one planted. The dollar value of these trees is immense.