Well, here's a great article on Christmas Trees. This time I'm just plain cutting and pasting from the NYT since I suspect you won't be able to access the article in a few days. (But if you'd rather check out the original, just go here.)
Q: What is the environmental impact of the loss of evergreens for Christmas trees?
A. In countries like the United States, where there is a big industry that grows Christmas trees rather than having thousands of people raid natural forests, growers say that the loss of the trees' services to absorb greenhouse gases is minimized.
But Dr. Allen Hershkowitz, senior scientist at the Natural Resources Defense Council, argues that tree farming is really the lesser of two evils. He points out that the trees have a short replacement cycle, harvested every six to nine years, and are grown quickly with chemicals to suppress competing flora, stimulate growth and kill pests. These herbicides, fertilizers and insecticides run off and add to water pollution, Dr. Hershkowitz said, and birds are deprived of food.
The frequent disruption of the soil also releases the greenhouse gas carbon dioxide, he said, "so much of the benefit of growing Christmas trees in terms of absorbing greenhouse gases is undermined," he argued.
Proper disposal of used trees is also important. "If burned, they generate nitrogen oxides, which contribute to smog, and even properly chipped and mulched, they release carbon dioxide," Dr. Hershkowitz said.
Alternatives present their own problems. "Artificial trees come overwhelmingly from nonrenewable petroleum-based products, and refining them also produces some of the most hazardous chemicals," Dr. Hershkowitz said. If practical, it would be better to plant a growing tree in the yard and decorate it for years, or skip greenery altogether, he said.