Which is the “greener” Christmas tree, real or artificial?

New York Times : Which is better for the environment? A real pine tree or an artificial one? John Collins Rudolf takes up the question in his New York Times article. “The natural tree is a better option,” answers Jean-Sébastien Trudel, founder of Ellipsos, a Montreal environmental consulting firm that released an independent study in 2009. The firm found that an artificial tree would have to be reused for more than 20 years to be greener than buying a fresh-cut tree annually, because of such factors as the carcinogens produced during manufacture, the nonrecyclable plastic and metal used in their construction, and the shipping from Asia where most of them are made. Living trees, in contrast, contribute oxygen to the atmosphere while growing and can be composted or mulched after use.