Real versus fake Christmas trees: Which is more environmentally friendly?

The typical rules of sustainability do not apply when it comes to choosing the most environmentally friendly Christmas tree.

The Christmas tree debate on real versus artificial, and which is better for the environment, has been ongoing for decades, Gary Chastagner a professor of plant pathology at Washington State University who has earned the nickname "Dr. Christmas Tree" for his extensive research on them, told ABC News.

When it comes to the centerpiece of Christmas decorations, the alternative that gets discarded at the end of every holiday season is, almost counterintuitively, the greenest way to go, according to experts.

Being able to reuse artificial trees year after year is convenient, but it doesn't make them the most sustainable option.

"The common misconception starts in longevity," Rosa Rivera, philanthropy officer for nonprofit organization One Tree Planted, told ABC News. "Artificial Christmas trees can last many years if they're well cared for, which kind of seems to make them the obvious sustainable choice, but they do have drawbacks."

Here is why real Christmas trees are better for the environment than fake trees:

Christmas tree farms help to produce oxygen and sequester carbon

The general consensus among plant experts is that, from a carbon lifecycle standpoint, the amount of oxygen released from the trees compared to the relatively low amount of energy it takes to produce them makes real trees more sustainable than artificial trees, Chastagner said.

Through photosynthesizing, the trees take carbon out of the atmosphere, combine it with water, and then releases clean, breathable oxygen, Bill Ulfelder, executive director of The Nature Conservancy, told ABC News.

Christmas trees are a renewable agricultural crop, Chastagner said. For every tree that is harvested, growers typically replant at least one seedling, sometimes more, he added.

Sustainable tree farms will grow and cut in phases, leaving certain sections open for harvesting each year and keeping others closed to give space for younger trees to grow, Rivera said.

The tree is then grown for seven to 10 years before it is harvested, and during that time it is sequestering carbon and releasing oxygen.

Separately, there is likely not much of an environmental difference among choosing different species of Christmas trees, Chastagner added.

"Some are a little shorter rotation than others, but they take about the same length of time to produce those trees," he said.

Purchasing at a Christmas tree farm also bolsters the local economy, as most tree farms are family-owned, Chastagner said.

Artificial tree production has a high carbon footprint

While real Christmas trees provide environmental benefits during their planting and growth, the greenhouse gases emitted during the production of artificial trees, most of which are made of plastic and metal, actively contribute to global warming.

The production of one artificial Christmas tree results in about 88 pounds of carbon dioxide -- an output 10 times higher than that of any sustainably grown real Christmas tree, Rivera said.

"There's a really important dimension to the growth of a real tree versus the fabrication or making a factory of a plastic tree that's using a bunch of fossil fuels," Ulfelder said.

An artificial tree must be kept for at least 10 years in order for it to have the same carbon utilization impact as purchasing a real Christmas tree each year, Rivera said.

Real trees are recyclable and biodegradable

A "distinct advantage" real trees have over fake trees is that there are recyclable, Chastagner said.

Some tree farms even make the trees available in pots or balled in burlap so that they can be replanted at the end of the season, averting the need to recycle altogether, Chastagner said.

Many cities have Christmas tree recycling programs in which the trees are chipped and turned to mulch. In New York City, that mulch is supplied to parks around the five boroughs, Ulfelder said.

In addition, many environmental and animal welfare organizations take the mulch for different purposes such as beefing up riparian areas, which is the interface between land and a river or stream, and also protecting dunes, sheltering wildlife and providing animal enclosure enrichment, Rivera said.

For crafty consumers, the trees can be cut up and used as natural drink coasters or creating vine frames for gardens, Rivera added.

Once an artificial tree hits a landfill, it could take thousands of years or more to break down, adding even more pollutants to landfills and oceans, Rivera said.

"We highly advocate to recycle your real trees and make the most out of them," Rivera said.

Make sure to properly care for the tree once at home

The most important thing for consumers to do once they purchase a real tree is to make sure it is properly displayed in a water-holding stand so that it can retain water, Chastagner said.

"Numerous studies have shown that if you take a fresh cut tree and display it in water and maintain it in water, not only does it maintain the water content in the trees, but it also significantly reduce problems with needle shedding," he said.

Fresh cut trees have the potential to use about one quart of water per inch of stem diameter, meaning a tree with a four-inch diameter in its stem needs to be placed in a stand that can hold at least one gallon of water.