Live trees actively photosynthesize as they grow from saplings, which removes carbon dioxide from the atmosphere. After they have been cut and Christmas is over, they're usually chipped for mulch. As mulch, the bits of tree very slowly decompose, releasing carbon dioxide back into the atmosphere. So in the end, a real Christmas tree is carbon neutral, putting the same amount of carbon dioxide back into the air as it took out (albeit much more slowly).
The tree farms that grew the trees also replant after the trees are cut.
trees, on the other hand, don't come out even in the carbon balance. Petroleum is used to make the plastics in the trees and lots of carbon dioxide-creating energy is required to make and transport them.
Because these trees just end up in landfills after a few years' use, "those greenhouse gases are lost forever," Springer said. "There's really no opportunity to recycle those."
Buy a real Christmas tree this year.