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Column: You can calculate benefit of trees


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“Trees are good.” It’s a sound bite used by the International Society of Arboriculture that attempts to capture that shared sense that trees provide many benefits.

From technical applications, such as strip mine reclamation to shading the yard, we know that trees have value. But how much?

The Council of Landscape and Tree Appraisers counts at least four methods for estimating the dollar value of a tree in the landscape. It’s an inexact science but one that is used every day to settle insurance claims or to estimate the contribution of mature trees to the real estate value of a property.

Another way to look at tree value is in a tree’s delivery of environmental services. Even though we may believe that “Trees are good,” that’s not enough in the world of tight budgets where it is often necessary to justify the expense of maintaining or protecting public trees.

Those environmental services have a dollar value, and the profession has now found ways to estimate those contributions, tree by tree.

The National Tree Benefit Calculator, an online tool, asks you for ZIP code, location type, species and diameter, rewarding you with several figures estimating the environmental services provided by the tree.

Taking the two remaining trees at the Bartholomew County Annex on State Street as an example, we learn that, together, they:

Capture about 13,000 gallons of stormwater each year.

Help to conserve about 254 kilowatt hours of energy for cooling annually.

Capture about 240 pounds of atmospheric carbon each year.

Absorb pollutants, intercept particulates, release oxygen, and help to reduce the production of ozone and other pollutants.

How to determine values

To have a look at one of the methods used to estimate the dollar value of a tree in the landscape, see extension.purdue.edu/extmedia/FNR/FNR-473-W.pdf

One online tool for determining environmental services value of trees, called the National Tree Benefit Calculator, can be found at treebenefits.com/calculator

Given weather patterns that include more severe events and unprecedented flooding, stormwater avoidance numbers might get serious attention. Most cities and towns know what it costs to handle stormwater and can do the math on what lost trees might cost them. Power savings also is a plus on several fronts, depending on how it is generated, and could include reduced cost, avoidance of pollutants and greenhouse gases from generation, and avoidance of the health impacts and costs related to illnesses that can be made worse by emissions.

So how about the estimated dollar value of those trees as real estate? Depending on the formula you use, the value could range into the tens of thousands.

The formulas place the highest values on a healthy tree with a full, live crown, since a small, stunted or half-dead tree does little in the way of environmental services or real estate value. Given the challenges of drought — fading in memory but still killing trees — and insects such as emerald ash borer and other pests, trees need the best possible care to reach that full live crown stage.

Start with best practices for planting, mulching and watering. (Tear down any mulch volcanoes in your life.) Avoid the damage that comes from over-fertilizing. (Any fertilizer is usually too much.) With mature trees in the landscape, a regular cycle of pruning (not topping) is a good habit to develop.

Now that we have national standards for pruning and a system for arborist certification, hiring an arborist for tree work isn’t nearly the mystery it used to be. Standards for protection during construction exist, which can help to preserve trees and their value when things are being torn up.

For more on any of these items, feel free to contact our office. We’ll be happy to get you the information you need so that all of your trees are good.

Kris Medic is Purdue Extension Bartholomew County’s interim extension director. Her program areas are agriculture, natural resources, economic and community development. She is a board-certified master arborist. She can be reached by email at kmedic@purdue.edu or by calling 379-1665.

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