Calculating the value of the tropical, urban tree Albizia saman

Abstract

This study compared estimated appraised value of trees using cost- and benefit-based approaches. Benefit-based appraisals provide estimates which highlight the relative contribution of different benefit types. Cost-based approaches are linked to regional market and nursery stock prices and/or tabulated through a point rating system with the inclusion of a monetary factor. The approaches used were the Council of Tree and Landscape Appraisers trunk formula, and the Helliwell approach. There were striking differences in the appraised value of the same trees (Albizia saman) between the two methods but this tended to be limited to trees of smaller girth sizes. The proposed benefit-based approach used in this study used a product score obtained through the rating of some 11 attributes/factors with no association to a monetary conversion factor (MCF). The same tree species used as in the cost-based methods were used in the benefit-based approach but this approach required the selection of four different specimens ranging from weak to highly desirable. The data collected showed that on each extreme end of the scale, there was some 98.6% difference in appraised value of trees. The key objective in the development of this proposed methodology was to allow for a rapid, effective decision-making process on tree removal and/or replacement for field arborists. Where the situation warrants a cost-based system for issues such as compensation, there are already established cost-based methodologies in place, which can serve this purpose. There is, therefore, no added advantage to introduce a new system with a MCF; rather a simplistic benefit-based methodology was an advantageous alternative. This provided fair and reasonable estimates of the value of trees by illustrating the relative contribution of the different benefits. Ultimately, the employment of both cost- and benefit-based methodologies may be necessary in some situations where a holistic approach is required for tree valuation. Although assigning a monetary value to a tree is based predominantly on the perception of the appraiser, establishing the value of trees is still fundamental to arboriculture and urban forestry. Without an estimate of tree value, there is little to motivate investment in tree management.