How Much Is A Tree Worth?
"Using satellite imagery and aerial photography, [a]nonprofit organization [American Forests] documented the gradual decline of the region's urban canopy, an area covering 3.2 million acres, as a result of sprawl and development...While the study shows today's trees are providing financial and ecological benefits worth millions of dollars, millions more would have been saved and the environment would have remained cleaner if more trees had been retained and protected during the study period." [Link to 12-page report in PDF format (1.04MB - approx. 2.5 minutes at 56kbps). Report includes color maps.]
Thanks to Abhijeet Chavan