"For the real Christmas tree, cultivation (planting, fertilizing, watering, etc.) is the largest contributor of environmental impacts, with one exception. The end-of-life phase of the real Christmas tree results in the largest contribution of greenhouse gas emissions in the real Christmas tree’s life cycle. This difference is, in part, due to modeling decisions concerning the handling of carbon sequestration in the cultivation phase and carbon release in the end-of-life stage.This calculation that an artificial tree used for more than five years has less environmental effect than a series of one-year natural trees is consistent with previous research. My discussion of studies done a few years ago, including the previous time that the American Christmas Tree Association commissioned a life-cycle analysis on this question, is here.
"For the artificial tree, the raw materials used in manufacturing, specifically polyvinylchloride followed by steel sheets, comprises the largest source of impacts in the artificial tree. Among the various life cycle phases, raw materials and transportation are seen to have largest impacts. Raw materials are primarily responsible for greenhouse gas emissions, eutrophication of water sources and use of non-renewable energy. Transportation mainly causes acidification of water, air and soil and smog in the atmosphere.
"Given the quantification of environmental impacts across both of the trees’ life cycles, a comparative assertion shows the breakeven point between the two trees is 4.7 years. That is to say an artificial tree purchased and used for at least 4.7 years demonstrates a lower contribution to environmental impact than 4.7 real Christmas trees purchased over 4.7 years."