At Science 2 dot 0, Kimberly Crandell considers real versus artificial trees from an environmental perspective. A nugget:
While chopping down a living tree may see like the most un-environment friendly thing you can do, in this situation it actually appears to be the “greener” choice. Because it’s not so much about how many uses you can get from your tree… as it is about what the tree is made of, and what it does to the environment when it is created and when you dispose of it.
Artificial trees are manufactured using a polyvinyl chloride (or PVC), which is a petroleum-derived plastic. The raw material for fake Christmas trees is both non-renewable and polluting. Furthermore, PVC production results in the unhealthy emission of a number of carcinogens, such as dioxin, ethylene dichloride and vinyl chloride.
More at the link.