According to the US Energy Information Administration (EIA) estimates, in 2006 urban trees accounted for nearly all (90 percent) of the carbon sequestration attributed to the combination of urban tree growing, plus land-filled yard trimmings and food scraps. [We assume that the sequestration tons for yard waste and food scraps are for landfilling. Compost degrades relatively fast.] Via:USEIA, Energy Information Administration, Office of Integrated Analysis and Forecasting U.S. Department of Energy, Emissions of Greenhouse Gases in the United States 2007 Available as ftp download of pdf file here.Because of the high rate at which US cities have been sprawling for the last 20 years (with both urban and suburban plantings now filling in) it's no surprise that the short-term C02 sequestration value has been going up.
Although the definition of "urban" is quirky, it would be interesting to subtract from the tree sequestration values, carbon lost from trees cut to make way for sprawl. But who knows how much wood was cut each year, and how much was landfilled vs burned vs turned into mulch?
Deep In the Forest
Urban Tree Salvage: Saving Forests with City Trees
Urban Tree Harvest
Backyard Fruit Trees A Barely Tapped Resource For Urban Gleaning ...
Urban Hardwoods: Saving Forests One Tree At A Time