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Long Live Trees

Jeff Harlan Esq., LEED AP

In the pantheon of environmental activists, Dr. Martin Luther King, Jr. isn’t the first person to come to mind. And while usually known for his contributions to the nation’s civil rights movement in the 1960’s, Dr. King often wove a thread of environmentalism in his speeches. He is widely cited as stating, “Even if I knew that tomorrow the world would go to pieces, I would still plant my apple tree.”

Dr. King’s suggestion that we should always care for our natural resources and be good stewards for future generations has some new scientific support. In a recent study of nearly 700,000 trees, 37 scientists from 16 nations determined that, contrary to other animals and living things, trees grow faster the older they get.

Contrary to many other living things, trees grow wider and faster the older they get.

Contrary to many other living things, trees grow wider and faster the older they get.

According to the study, published in the January 2014 issue of Nature, tree growth rate increases continuously as trees get bigger and bigger. While trees seem to reach a height limit, they continue to add mass and get wider with age.

Co-author Nate Stephenson, a forest ecologist with the U.S. Geological Survey based in California’s Sequoia and Kings Canyon national parks (home to some of the world’s largest and awe inspiring trees), explains, “It’s as if, on your favorite sports team, you find out the star players are a bunch of 90-year-olds. They’re the most active. They’re the ones scoring the most points.”

This is particularly important in considering the role trees play in reducing carbon dioxide, the gas most commonly associated with climate change. Trees naturally absorb carbon dioxide from the air and store it as carbon in their wood; and the older, larger ones do it in greater quantities.

So if you were to draft an All Star team to combat climate change, you’d pass on the flashy rookie sapling and load up on the (very) seasoned veteran trees. A solid bench of mature trees—an old growth forest, for example—holds a lot of carbon.

Sustainable forestry practices can ensure that beautiful wooden architecture can be enjoyed for many generations to come.

Sustainable forestry practices can ensure that beautiful wooden architecture can be enjoyed for many generations to come.

And while growing bigger, more mature trees is a sustainable forestry practice, it also has practical applications. There’s a story about a building at New College in Oxford, England, where the main hall, built in the 1600s, was constructed with huge oak beams. By the 1950s, the 40-foot long by 2-foot thick beams were rotting, and replacing them at current prices was prohibitive.

The school’s building committee ultimately consulted the College Forester, who replied, “We’ve been wondering when you would ask this question. When the present building was constructed 350 years ago the architects specified that a grove of trees be planted and maintained to replace the beams in the ceiling when they would suffer from dry rot.” Clearly a forester with foresight understands how long-term stewardship and resource management plays a critical role in our natural and built environments.

Selecting the appropriate location for urban trees can mean the difference between growing an asset and planting a liability.

Selecting the appropriate location for urban trees can mean the difference between growing an asset and planting a liability.

Cities across the United States are focusing on improving their green infrastructure, expanding tree planting and instituting sustainable management practices to optimize the benefits trees provide. New York City is one of the most well-known examples, and Great Ecology’s assessments of and restoration designs for the Central Park Woodlands illustrates how communities can improve a resource’s functionality in an urban context.

Promoting long-term growth of trees also depends on understanding how these living organisms require certain planting conditions to survive and thrive. In their recently released paper, “Trees in Urban Design,” professional engineer Paul Crabtree and certified arborist Lysistrata Hall offer a set of principles and tools to guide effective and sustainable tree planting in our city streetscapes. One of these principles—design the tree from the roots up—recognizes the idea that trees need sufficient space, especially in urban conditions.

Large trees need up to 1000 cubic feet of soil for their roots.

Large trees need up to 1000 cubic feet of soil for successful planting.

Selecting the appropriate tree for a particular location can mean the difference between growing an asset and planting a liability. For example, comparing one tree planted in 150 cubic feet of soil to the same tree in 1,000 cubic feet, the former provides about -$3,500 net lifecycle costs, while the latter provides over $25,000 in benefits during its longer lifetime. According to Crabtree and Hall, a tree in less soil would have to be replanted five times because its lifespan is only 7-10 years (in comparison to one tree in significantly more soil living 50+ years).

So the next time you gaze at a towering redwood in an old-growth forest, admire the wood-beamed structure of a building, or enjoy the beauty and shade of a canopied street, think of those who planned for the long-term. In Dr. King’s words, this kind of stewardship will ensure the “world will not go to pieces.” Knock on wood.

About the Author:

Jeff Harlan, Senior PlannerJeff Harlan is Great Ecology’s Senior Planner with over 15 years of experience as a community planner, specializing in sustainable development, strategic planning, and environmental design. Trained as an environmental attorney, Jeff has an expert knowledge of community development and brings a unique approach to complex land use problems.

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