[en] Results of the 3-year Chicago Urban Forest Climate Project indicate that there are an estimated 50.8 million trees in the Chicago area of Cook and DuPage Counties; 66 percent of these trees rated in good or excellent condition. During 1991, trees in the Chicago area removed an estimated 6,145 tons of air pollutants, providing air cleansing valued at $9.2 million dollars. These trees also sequester approximately 155,000 tons of carbon per year, and provide residential heating and cooling energy savings that, in turn, reduce carbon emissions from power plants by about 12,600 tons annually. Shade, lower summer air temperatures, and a reduction in windspeed associated with increasing tree cover by 10 percent can lower total heating and cooling energy use by 5 to 10 percent annually ($50 to $90 per dwelling unit). The projected net present value of investment in planting and care of 95,000 trees in Chicago is $38 million ($402 per planted tree), indicating that the long-term benefits of trees are more than twice their costs

[en] Large-scale urban tree planting is advocated to conserve energy and improve environmental quality, yet little data exist to evaluate its economic and ecologic implications. This paper describes an economic-ecologic model applied to the Trees for Tucson/Global ReLeaf reforestation program. The program proposes planting 500,000 desert-adapted trees before 1996. The computer simulation accounts for planting locations, planting rates, growth rates, and mortality rates when projecting average annual benefits and costs. Projected net benefits are $236.5 million for the 40-year planning horizon. The benefit-cost ratio and internal rate of return for all trees is 2.6 and 7.11, respectively. Trees planted in parks are projected to provide the highest benefit-cost ratio (2.7) and trees along residential streets the lowest (2.2). Tree removal costs are the most important management expense and air conditioning energy savings provide the greatest benefits. Average annual cooling energy benefits per tree are projected to be 227 kWh ($16.34) for evapotranspirational cooling and 61 kWh ($4.39) for direct shade. Ninety-seven percent (464 lb) of the total carbon conserved annually per mature tree is attributed to reduced power plant emissions

[en] Urban trees can produce a number of benefits, among them improved air quality. Biogenic volatile organic compounds (BVOCs) emitted by some species are ozone precursors. Modifying future tree planting to favor lower-emitting species can reduce these emissions and aid air management districts in meeting federally mandated emissions reductions for these compounds. Changes in BVOC emissions are calculated as the result of transitioning to a lower-emitting species mix in future planting. A simplified method for calculating the emissions reduction and a Tree BVOC index based on the calculated reduction is described. An example illustrates the use of the index as a tool for implementation and monitoring of a tree program designed to reduce BVOC emissions as a control measure being developed as part of the State Implementation Plan (SIP) for the Sacramento Federal Nonattainment Area. - Highlights: → A Tree BVOC index based on reduced emissions from low emitting trees is described. → An example illustrates use of the index as an implementation and monitoring tool. → This index could be useful for including urban trees in air quality mitigation plans. - A tree BVOC index is presented that calculates reduced BVOC emissions from planting lower-emitting urban tree species that has potential application for SIP compliance.