Is the Common Tree Leaving an Uncommonly Large Carbon Footprint?

The Boston Common tree is a great tradition, but some scientists day it's not so great for the environment.

When thousands of lights flicker on, illuminating the 50-foot tree at Thursday night's , most people won't be thinking about carbon footprints or just how "green" the tree is. 

After a four day trek, the white spruce arrived Friday, Nov. 26 on a flatbed truck. It was wrapped in pine branches to prevent it from drying out during the trip. However, the nearly 600-mile journey from Nova Scotia to Boston, and the tree farming process in general, have some scientists taking a closer look at the environmental impact of the tradition. 

Bill Moomaw, professor of International Environmental Policy at Tufts University, said the process of obtaining a carbon footprint is bigger than just removing the one tree to send a thankful gesture. 

"I'm sure it's more carbon to bring it down here on a truck that emits about 10 pounds of carbon every mile, than to leave the tree there and provide nutrients for the ecosystem," he said. "It's a nice gesture they cut this beautiful tree and give it away, but I think it's useful to raise a question of why do we do this? Is it just because it endures?"

Choosing the right tree

Residents of Nova Scotia first began sending over Christmas trees 39 years ago as a 'thank you' gift to Boston for the city's rapid assistance to a devastating munitions ship explosion in Halifax Harbor in 1917.  

Tree farming brings in about $25 million per year to Nova Scotia's economy, said Nova Scotia Department of Natural Resources Communications Adviser David Salter. Some 1,200 families are involved in the cultivation of nearly 2 million Christmas trees each year. Giving back takes precedence in this tradition, and Nova Scotians believe this is the most appropriate gift they can give to Bostonians during the Christmas season, he said.  
"The Boston tree is about Nova Scotians showing their gratitude with this symbol of thanks for helping in our time of need," Salter said. 

The Department chooses the winning tree based on how easy it is to access and how uniform and symmetrical it is. The tree must be 40 to 50 feet high, and be healthy with a medium to heavy density. The attractive winner is usually a Balsam fir, red spruce or white spruce, which grow an average of 75 to 100 years. To be as shapely as past winners, the tree is typically grown out in the open.

Environmental costs

In 2009, the city of Boston began to come up with ways to improve energy costs and become more environmentally friendly for the ceremony. For the first time, the lights on smaller trees lining the Boston Common and the main stage were LED lights, which use 10 percent less energy than typical holiday lights, said  Executive Director Mary Hines. 

The lights were just one step in the process of making the ceremony more sustainable. After each holiday season is over, the trees are turned into compost, which is then used locally, she said.

But some environmental scientists say sustainability could be in jeopardy if the methods of obtaining the trees are not changed in the future.

Peter Busher, Natural Sciences Division Chair at Boston University's College of General Studies, said if you look at the entire Nova Scotia Christmas tree industry, you would have to account for the carbon the trees remove from the atmosphere versus the amount released when they are "recycled."

"I think that you will find that the input of carbon to the atmosphere is considerable," Busher said. "You have to consider that cutting the trees stops them from removing carbon from the atmosphere, the use of 2-cycle chain saws to cut them, which produce very high emission for small equipment, and also their ultimate disposal (by burning) will be rapid carbon emissions."

But Matthew Wright, executive director of the Christmas Tree Council of Nova Scotia, said while cutting down one tree may contribute negatively to the carbon cycle, that tree also produced oxygen for all the years of its life, equaling close to a half acre or more.

"So, the amount of oxygen produced is enormous compared to the amount of carbon when it travels," he said. "When I look at the balance of things, it strikes me that the potential human enrichment that this tree offers outweighs a lot of other things." 

Wright said open grown trees chosen as exports are also cut at the height of their lifecycle because once a tree becomes too mature, it burns more oxygen than it produces.    

But from a carbon cycle viewpoint, Moomaw, from Tufts, said it would be better to leave the tree growing. But it seems using a plastic, recyclable tree wouldn't have the same effect. 

"The tree provides so much joy to so many people throughout its life," Boston Parks Director Hines said. "It's a huge deal that the people of Nova Scotia continue to do this for our city each year." 


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