By Michael “House” Tain
Tree appraisal is the term used to describe the valuation of trees in the landscape. And although many an ol’ crusty climber or feller may jump to discussions of board feet, tree appraisal is actually something quite different than how many truckloads of clear grain lumber might be gotten out of that big oak. Tree appraisal puts a value on trees either existing in the landscape, or removed from the landscape. And although timber value could play a role, more often the question to be decided is how much the tree adds, or did add, to the value of the property along with what monetary value it would take to replace the tree if possible. Tree appraisal is not necessarily a precise process; and can be quite problematic if litigation is involved. In reality, the valuation of trees is a skill — like so many in the tree care industry — that takes a good deal of education, training and experience to master; and in many cases is best left to specialists such as consulting arborists who focus on tree appraisal. However, some basic knowledge of terms and methods can assist crew members in not only understanding tree appraisal, but also help them realize whether or not it is a subspecialty in which they are interested in pursuing further training and education.
There are a variety of methods for tree appraisal. An excellent primer to the whole process is the “Guide for Plant Appraisal” available from the International Society of Arboriculture. But three basic methods are replacement cost, loss in assessed value, and formula. Arborists new to the idea of tree appraisal should not only get a copy of the “Guide for Plant Appraisal,” but also select whichever of the three basic methods is simplest and most appropriate to the tree(s) to be appraised.
This method is often the simplest to compute, but also one that is only going to be appropriate in very specific circumstances. In short, the appraiser gathers information on what would be the cost of replacing the trees from a local nursery — factoring in all the costs involved such as planting, removing the damaged/dead trees to be replaced, etc. Obviously this method is primarily going to be applicable to smaller trees in a landscape, as even the most experienced and motivated arborists do have some limits on how large a tree can be purchased, moved and transplanted. In some cases, the appraisal may not involve trees that have been damaged or removed, but simply a curious customer wishing to know the value of their woody friends. Once again, for smaller trees this is a fairly simple estimation, but one that does not necessarily take into account the value the trees bring to the ecosystem of the landscape or aesthetically.
Loss in assessed value
This is also a fairly simple method, but one that in most cases will involve consulting with another professional such as a Realtor or property assessor. The goal in this method of tree appraisal is to come up with a monetary amount that the tree or trees add, or did add, to the home or property. Digital photography is quite valuable in the use of this method, particularly when the tree(s) are still in existence. The basic process is to have the real estate or property professional estimate the value of the home/landscape both with and without the trees. In the case of trees that have been damaged or destroyed, simple before-and-after pictures will suffice for an estimate. When the trees are still present, and the goal is to put a number on their effect on the assessed value, any number of photo editing tools can be used to remove them from the digital pictures used in the assessment.
This method is one that is widely used; and is particular helpful in the case of large trees that are difficult, if not impossible, on which to put a replacement value. Just as there are several methods available for tree appraisal, there are also different formulas available. But a relatively simple one involves the following factors: cross section area, base value, species class, condition class, and location class. These factors are multiplied together to arrive at a tree value; and will certainly require further training, education, and the “Guide for Plant Appraisal” for any interested users.
- Cross section area: There are tables available to determine this value, but, in short, it expresses tree size in a number that works with the formula. Quick and dirty it can be determined by squaring the diameter then multiplying that value by 0.7854. An example would be a 10-inch diameter tree results in 100 X 0.7854, which equals a cross section area of 78.5 inches.
- Base value: This is the amount that one cross section unit of a tree’s trunk is worth. It is determined by finding the cost of a replacement tree from a nursery — typically the largest available — and then dividing that number by the cross section area to arrive at a value per square inch. This allows the user to place a value per square inch on trees for which a replacement is unavailable. In the 10-inch-diameter tree example used earlier, the appraiser would most likely use the base value from a smaller tree, which, when multiplied by the cross section area, would translate roughly to the size of the tree to be valued/replaced.
- Species class: This factor refers to the species of the tree to be valued; and has to do with positive, or negative, characteristics of that species. It is assigned a percentage value from 1 to 100 percent; and is then converted to a decimal figure prior to “plugging into” the formula. Flowering, fruit, form, and the many other characteristics of differing species can help the appraiser determine the species class, but there are also tables readily available that delineate various species classes for different geographic locations.
- Condition class: The condition class is one with which a professional arborist should be quite comfortable, as it has to do with the condition of the tree — something every crew should determine as part of their tree risk assessment prior to working on a tree. Once again, it is assigned a value from 1 to 100 percent, which is then converted to a decimal figure for formula use. This is also an area in which the arborist’s knowledge of species characteristics can come into play, as some species deal with, and survive, defects and diseases better than others. Once again, there are descriptions/tables available to help novice appraisers better assign a condition class to a particular tree.
- Location class: This factor attempts to value what the tree brings to the site both in beauty and in brawn. It is certainly a factor that asks much of the appraiser’s judgment, although there are helpful guides available. The aesthetic impact of the tree is considered, along with functional attributes it possesses (wind break, shade, screening), as is its actual location and importance in the landscape. As previously, location value is rated from 1 to 100 percent and converted to decimal form.
This should be considered as no more than a basic introduction to tree appraisal, but it does provide some terms and concepts that can help interested arborists start down the road toward providing a value to the woody friends they work on, and in, every day. As can be seen from the brief descriptions shared here, tree appraisal can be a complex process that involves a variety of disciplines — from basic mathematics to aesthetic judgment. But once understood and practiced, tree appraisal can be an excellent tool in any professional arborist’s mental toolbox.
Michael “House” Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions www.northamericantrainingsolutions.com and Arbor Canada Training and Education www.arborcanada.com. He is currently located in Lancaster, Ky., and can be reached via e-mail at email@example.com