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About 350 million trees grow on Christmas tree farms in the United States, according to the National Christmas Tree Association. About 30 million of these trees are harvested annually.These farms have environmental costs of their own, noted Thomas Harman, who sells artificial Christmas trees. “If you use an artificial tree for 10 years, you need 10 trees, and that is 70 years’ worth of growing trees,” he told Weather.com in 2013. "You have 70 years of water and pesticide consumption."Researchers say, however, that pesticides aren't actually too much of an issue on Christmas tree farms.“If you look at the continuum of chemical use in U.S. agriculture, Christmas trees production certainly ranks on the low end,” Cregg told Mother Jones in an earlier interview.Christmas tree farms can also serve as important habitats for local birds, insects and other wildlife.