New York, Dec. 19: When it comes to Christmas trees, Americans increasingly prefer plastic pines over the real thing. Sales of fake trees are expected to approach 13 million this year, a record, as quality improves and they get more convenient, with features like built-in lights and easy collapsibility. All told, well over 50 million artificial Christmas trees will grace living rooms and dens this season, according to the industry’s main trade group, compared to about 30 million real trees.

Ms Kim Jones, who was shopping for a tree at a Target store in Brooklyn this week, was convinced that she was doing the planet a favour by buying a $200 fake balsam fir made in China instead of buying a carbon-sipping pine that had been cut down for one season’s revelry.

“I’m very environmentally conscious,” Ms Jones said. “I’ll keep it for 10 years, and that’s 10 trees that won’t be cut down.” But Ms Jones and the millions of others buying fake trees might not be doing the environment any favours.

In the most definitive study of the perennial real versus fake question, an environmental consulting firm in Montreal 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. The calculations included greenhouse gas emissions, use of resources and human health impacts.

“The natural tree is a better option,” said Mr Jean-Sebastien Trudel, founder of the firm, Ellipsos, that released the independent study last year.

The annual carbon emissions associated with using a real tree every year were just one-third of those created by an artificial tree over a typical six-year lifespan. Most fake trees also contain polyvinyl chloride, or PVC, which produces carcinogens during manufacturing and disposal.

Ellipsos specifically studied the market for Christmas trees bought in Montreal and either grown in Quebec or manufactured in China. Mr Trudel said the results would most likely differ for other cities and regions. Excessive driving by consumers to purchase real trees could tip the scales back in favour of artificial trees, at least in terms of carbon emissions.

Over all, the study found that the environmental impact of real Christmas trees was quite small, and significantly less than that of artificial trees — a conclusion shared by environmental groups and some scientists.

“You’re not doing any harm by cutting down a Christmas tree,” said Mr Clint Springer, a botanist and professor of biology at Saint Joseph’s University in Philadelphia. “A lot of people think artificial is better because you’re preserving the life of a tree. But in this case, you’ve got a crop that’s being raised for that purpose.”

Makers of fake trees argue that the environmental evidence isn’t quite so clear-cut.“If you buy an artificial Christmas tree and reuse it for at least five years, it’s absolutely a green thing to do,” said Mr Thomas Harman, founder and chief executive of Balsam Hill, a maker of premium artificial trees. He said that the average amount of car travel by consumers to buy a real Christmas tree outweighed the added energy and pollution costs of buying an artificial tree from China.

The American Christmas Tree Association, the main trade group for artificial tree makers and retailers, says its own study found that it took 10 years of use before a fake tree became better for the environment than a real one, at least in terms of carbon emissions.

Yet the trade-offs are not immediately apparent to consumers and even some tree growers. The balance tilts in favor of natural Christmas trees because of the way they are grown and harvested.