The Value of Trees

How can we determine the value of trees? How can we measure the monetary value of the services and products a tree gives us. "Trees Make Effective Sound Barriers, Trees Produce Oxygen,Trees Become Carbon Sinks,Trees Clean the Air,Trees Shade and Cool,Trees Act as Windbreaks,Trees Fight Soil Erosion,Trees Increase Property Values" so says Steve Nix. A discussion can be seen here about the value of a tree. Even when they are interesting to read I doubt whether the true value of a tree can ever be measured in monetary terms.