304 Vogt et al.: The Costs of Maintaining and Not Maintaining the Urban Forest changes in pruning costs and condition class (Miller and Sylvester 1981). Cost was generated as the reduction in tree value as condition class declined for each one-year increase in the pruning cycle length; marginal return, or marginal benefit, was generated based on the net decrease in pruning costs as the pruning cycle was increased in increments of one year (Miller and Sylvester 1981). Comparison of savings in pruning costs versus reductions in tree population value suggested the optimal pruning cycle to be between four and five years (Figure 6b). Costs of not pruning The costs of not pruning trees have rarely been examined outside of the context of utility arboriculture or pruning cycles. The only study this literature review found that explicitly examines this question is Ryder and Moore (2013, see sidebar The Costs of Not Pruning). The Costs of Not Pruning Ryder and Moore (2013) have authored one of the few papers that explicitly examine the costs of not maintaining trees (i.e., de- ferring maintenance). These authors asked: “If a tree is formatively pruned in the early stage of life, what will the cost-saving be if the same defects had not been rectified?” (p. 17). Seventy-eight percent of all plant- ed trees in their sample showed structural defects that required formative pruning (Ryder and Moore 2013). Formative pruning costs (all currency is in AUD$) averaged $2.79 per tree, while structural pruning for a mature tree averaged $44.59 (Ryder and Moore 2013). The authors estimated that using inflation rates of 3%–5%, trees not formatively pruned today would cost $78 to $112 to structurally prune in 20 years (Ryder and Moore 2013). Thus, the cost of not per- forming formative pruning on recently plant- ed trees can be calculated as the difference between the costs of formative pruning plus normal structural pruning (~$48) and struc- tural pruning for non-formatively pruned trees ($78–$112), or between $30 and $64. Planting Kielbaso et al. (1982) and Kielbaso (1990) attrib- uted 14% of city forestry budgets expenditures to planting costs (the cost of the tree, labor, ma- terials, water, mulch, and other things at time of planting). Tschantz and Sacamano (1994) reported planting at 13.9%. Time-of-planting costs can account for 80% or more of total maintenance- related costs during the life of a tree (McPherson et al. 1997). Pauliet et al. (2002) reported results from a survey of cities in 17 European coun- tries that revealed street tree planting and estab- lishment costs range widely from EUR €250 to €1,875 (200–1,500 in 2002€). McPherson (2003) reported that planting and establishment costs vary by species, and range from USD $0.01 annu- ally per tree for hackberry (Celtis sinensis) ($0.01 annually in 1997$) to $3.16 annually per tree for ginkgo (Ginkgo biloba) ($2.18 annually in 1997$). McPherson et al. (1997) and others have argued that time-of-planting costs can be reduced signif- icantly by properly matching the tree to the site, which calls to mind the urban forest management axiom: right tree, right time, right place. Plant- ing and establishment practices can influence subsequent maintenance needs and costs. Harris (1985) argued that adequate root conditions for healthy establishment could make trees easier to maintain later in life. Chapman (1981) specified that proper tree selection could reduce annual maintenance costs “by 20 to 50 percent” (p. 316), a significant potential savings where mainte- nance costs can range “from 20 to 50 percent of the planted price” (p. 313); however, Chapman provided no numerical data to support purported monetary savings. McPherson (1992) stated that “funds spent initially to promote tree establish- ment, rapid growth and strong crown structure can reduce long-term tree care costs by prolonging the serviceable life of the tree” (McPherson 1992, p. 47); however, this article provided no long-term data to back this conclusion. McPherson (1992) suggested a specific accounting approach for tree- planting projects, and demonstrates the utility of the approach using the city of Tucson, Arizona, U.S. The author found that costs of planting ini- tially exceed the benefits of planted trees, but within five years of planting, benefits exceed costs at a rate of 3-to-1 or greater (McPherson 1992). ©2015 International Society of Arboriculture
November 2015
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