Even viewed conservatively, trees are worth far more than they cost toplant and maintain. The U.S. Forest Service's Center for Urban ForestResearch found a ten-degree difference between the cool of a shadedpark in Tucson and the open Sonoran desert. A tree planted in theright place, the center estimates, reduces the demand for airconditioning and can save 100 kilowatt hours in annual electrical use,about 2 to 8 percent of total use. Strategically planted trees canalso shelter homes from wind, and in cold weather they can reduceheating fuel costs by 10 to 12 percent. A million strategicallyplanted trees, the center figures, can save 0 million in energycosts. And trees increase property values, as much as 1 percent foreach mature tree. These savings are offset somewhat by the cost ofplanting and maintaining trees, but on balance, if we had to pay forthe services that trees provide, we couldn't afford them. Becausetrees offer their services in silence, and for free, we take them forgranted.