306 Vogt et al.: The Costs of Maintaining and Not Maintaining the Urban Forest Economics of removal decisions Two recent studies examine the economics of tree removal. Scott and Betters (2000) presented a method for evaluating on an economic basis whether to remove and replace a tree, or retain and maintain a tree. The authors advocated use of the individual tree appraisal methods (re- placement) developed by the Council of Tree and Landscape Appraisers (CTLA) to calculate the replacement value of a single tree as a type of capital asset, taking into account species, lo- cation, and condition. To extrapolate the benefits of a replacement tree (i.e., the value of a future tree), the authors used a discount rate of 2.5% per year. In considering only whether to remove a tree (regardless of replacement), they proposed calculating the present net value of the existing tree as the difference between benefits now and benefits in the future, less the discounted stream of periodic maintenance costs incurred over the time period between the present and the time at which the tree would be removed. In determining whether to remove and replace the tree, these au- thors added to the present net value of the existing tree the discounted “land expectation value,” or the value of a replacement tree with a given life expectancy assuming replacement recurs into the infinite future. Scott and Betters (2000) presented an example of applying their methods to a single elm tree (Ulmus americana) on the Colorado State University campus. Present net value of retaining the existing elm and engaging in maintenance (annual treatment) for a period of eight years was USD $95 ($70 in 2000$) (Scott and Betters 2000). Replacing the existing tree immediately yielded present net benefits of $92 ($68 in 2000$), while retaining and maintaining the tree for eight years and then removing and replacing yields benefits of $413 ($305 in 2000$) (Scott and Bet- ters 2000). Thus, for this example, the greatest benefit was to retain and treat the elm tree for eight years and then replace the tree with a Dutch elm disease- (DED) resistant elm (Scott and Bet- ters 2000). In this example, the “cost” of removal and replacement was the lost stream of benefits resulting from premature removal of the tree. Tinus and LaMana (2013) reframed tree removal costs by quantifying the economics of harvesting urban trees and recovering, as lumber and other ©2015 International Society of Arboriculture wood products, the wood waste that would other- wise have been disposed of in a landfill. Tinus and LaMana (2013) compared the value of recovered forest products and avoided landfill disposal costs to standard tree removal and disposal costs. They found an average avoided disposal cost per job site of USD $877, compared to an average hauling cost of $842, yielding only a marginal difference of $35 to landowners (excluding additional milling costs and the value of secondary products (Tinus and LaMana 2013). However, this analysis omitted the costs of hauling wood to a disposal site, although the cost of hauling wood to a milling site was included. In addition to the studies cited here, several others have examined the economic costs of tree removal and replacement decisions in the con- text of diseased trees or those threatened by pests or disease (see section "Pest and disease manage- ment" for a more complete discussion of pest costs). Non-economic costs of removal A non-economic (i.e., non-monetizable) cost of tree removal may be impacts on the remaining trees in the landscape. An interesting study by Kane (2008) examined the impact of recent maintenance activi- ties at a campsite, including pruning and removal of other trees, on the likelihood of the failure of trees at that site. He found that removal of other trees at a campsite increased the likelihood of root-related tree failures due to increased root exposure and increased exposure to winds and decreased crown contact with neighboring trees (Kane 2008). While this study did not explicitly examine costs, it can be inferred that an additional cost of tree removal, at a site where trees are in close proximity, increased risk of failure for the remaining trees at that site. Unlike the tree pruning in which pruning cycles can be increased (time between pruning events lengthened) during periods of budget crisis, the removal of dead and high-risk trees should never be deferred unless property dam- age and personal injury can be avoided by closure of areas with high-risk trees (e.g., closing a park area to avoid human contact). Of course, there are oſten costs to these alternative actions as well. If tree removal is deferred and alternate precautionary steps are not taken, the costs can include injury liability and damages paid in court settlements (see section "Tree risk management").
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