Do you know what the real value of a tree encompasses? When certified arborists evaluate the value of a tree they take into consideration the species, the location and the condition. Arbor Day Foundation website has a great on-line guide to finding the value of your tree. This is called the National Tree Benefit Calculator. The Tree Benefit Calculator uses formulas that certified arborists use. These can be very complicated and add in a great deal of factors. The Arbor Day Foundation has based their Tree Benefit Calculator on industry standards used by certified arborists to provide you with accurate information. The Arbor Day Foundation has broken down the process into various categories to demonstrate to you what is factored into the monetary value of a tree. Besides arborists, real estate agents and home buyers place a value on the trees which increase the value of a residential property between 10 to 23 percent.
What factors are involved in assessing the value of a tree? The industry standards that are factored into the value of a tree are property value, stormwater, energy, air quality and atmospheric carbon dioxide reduction. The property value of a tree is based on the square feet of the leaf surface area of the tree. One can expect that the leaf surface area will increase each growing season as the tree grows to maturity. So the older the tree and larger the tree, the more value it will add to your property. If you have a property with a large number of trees, you will have more leaf surface area. Naturally, real estate agents do tend to see trees on the property as great "curb" appeal.
Trees help with stormwater runoff. Think about the amount of leaf surface area and the water that can sit on the leaf surface and evaporate as well as the branches and bark surface. The root system of a tree can filtrate and store the rainwater runoff. The root system of a tree helps with erosion control. As an example, if you have a plum tree that is 10 inches in width at breast height, then your plum could potentially intercept 661 gallons of runoff water. With runoff water comes surface pollutants such as salts, oil or gasoline, other pesticide/herbicide residue and any other debris. With trees helping to intercept the runoff water, they are slowing or decreasing the amount of pollutants washed into community waterways.
With that same 10 inch plum, it will conserve 26 kilowatt hours of electricity for cooling and reduce consumption of natural oil or gas by 3 therm(s). It is easy to see how the leaf surface area of a tree can shade a home as well as reduce the wind speed. Transpiration adds to the cooling effect. The process of transpiration is the absorption of water through roots and the loss of water to the atmosphere through openings called stomata in the underside of the leaf surface. Add to this evapotranspiration the loss of water from the soil as well as the transpiration from the stomata of leaves and you get even more cooling effect.
As trees intercept rain water runoff, they also help intercept air pollutants. Leaves can intercept ash, dust and smoke as well as other pollutants such as ozone, nitrogen dioxide and sulfur dioxide. Plants in general, generate oxygen and use carbon dioxide in the process of photosynthesis. One mature tree can produce enough oxygen for 10 people for a year according to the Arbor Day Foundation.
Trees sequester carbon dioxide in their roots, trunks, branches and leaves as they grow. If a tree is harvested for wood, the carbon dioxide remains in the wood. So a 10 plum can reduce atmospheric carbon by 90 pounds. The amount of carbon sequestered varies from one species to another. According to the U.S. Department of Energy's Method for Calculating Carbon Sequestration by Trees in Urban and Suburban Settings, a one year old fast-growing hardwood sequesters 4 pounds of carbon a year. As the hardwood matures to 50 years, it sequesters 122.7 pounds of carbon a year. One acre of trees absorb enough carbon dioxide to equal the amount of carbon dioxide produced driving a car 26,000 miles according to US Forest Service.
Undoubtably, the value of a tree is more than monetary. The beauty they provide in our landscapes and the healing capacity they have can make them invaluable. Research is now finding that patients who are recuperating from surgery recuperate faster and need less pain medicine if they can view a tree from their hospital room window. Their are historical values placed on trees as well as emotional values. There are plenty of literary authors in the world that demonstrate our attachment to trees. "If you would know strength and patience, welcome the company of trees," by Hal Borland.
Here on the eastern plains of Colorado, we are grateful for the value of trees as windbreaks and shade trees. Trees have many different values. Understanding the type of tree you have and its cultural needs, goes along way to extending a tree's life, no matter how you value your trees.