This is pretty cool stuff when it comes to figuring out the value of trees in the environment (particularly in your neighborhood)
Pittsburgh did a study through Tree Pittsburgh to find out how much value the trees were adding to the city in terms of air They only sampled small plots of city-owned trees (not those on private property) to come up with some pretty interesting numbers,
“A 2011 analysis of Pittsburgh’s total tree cover, which involved sampling more than 200 small plots throughout the city, showed a value of between $10 and $13 million in annual benefits based on the entire urban forest’s contributions to aesthetics, energy use and air quality.” “Landscape Insider”, Feb 25.
i-Tree is a free tool for evaluating the value of trees. It’s open source and I have not played with it but if you know folks in your area who are in the tree business, you may want to pass these along.