Martha, but once they are burned or rot the CO2 goes back into the air, trust me on this one, I'm a science teacher
. This isn't politics it is the Law of conservation of matter. The CO2 stays 'locked up' while the tree is alive or the CO2 is in the form of wood. Most christmas trees are burned/pulped and the CO2 is recylcled back into the air.
Did they also factor in the fuel you burn fetching them and taking them to the dump?